Patient advocacy

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Patient_advocacy 

Patient advocacy is a process in health care concerned with advocacy for patients, survivors, and caregivers. The patient advocate may be an individual or an organization, concerned with healthcare standards or with one specific group of disorders. The terms patient advocate and patient advocacy can refer both to individual advocates providing services that organizations also provide, and to organizations whose functions extend to individual patients. Some patient advocates are independent (with no conflict-of-loyalty issues) and some work for the organizations that are directly responsible for the patient's care.

Typical advocacy activities are the following: safeguarding patients from errors, incompetence and misconduct; patient rights, matters of privacy, confidentiality or informed consent, patient representation, awareness-building, support and education of patients, survivors and their carers.

Patient advocates give a voice to patients, survivors and their carers on healthcare-related (public) fora, informing the public, the political and regulatory world, health care providers (hospitals, insurers, pharmaceutical companies etc.), organizations of health care professionals, the educational world, and the medical and pharmaceutical research communities.

Nurses can perform a de facto role of patient advocacy, though this role may be limited and conflicted due their employment within an organization. Patients can advocate for themselves through self-advocacy and the ability for this self-advocacy can be learnt or improved through training.

History

Patient advocacy, as a hospital-based practice, grew out of this patient rights movement: patient advocates (often called patient representatives) were needed to protect and enhance the rights of patients at a time when hospital stays were long and acute conditions—heart disease, stroke and cancer—contributed to the boom in hospital growth. Health care reformers at the time critiqued this growth by quoting Roemer's law: a built hospital bed is a bed likely to be filled. And more radical health analysts coined the term health empires to refer to the increasing power of these large teaching institutions that linked hospital care with medical education, putting one in the service of the other, arguably losing the patient-centered focus in the process. It was not surprising, then, that patient advocacy, like patient care, focused on the hospital stay, while health advocacy took a more critical perspective of a health care system in which power was concentrated on the top in large medical teaching centers and a dominance of the medical profession.

Patient advocacy in the United States emerged in the 1950s in the context of cancer research and treatment. In those early days of cancer treatment, patients and their families raised ethical concerns around the tests, treatment practices, and clinical research being conducted. For instance, they expressed concern to the National Institute of Health (NIH) about the cruelty of the repeated collection of blood samples (for blood marrow examination) and raised questions about whether this was more harmful than beneficial to the patient. Sidney Farber, a Harvard physician and cancer researcher, coined the term total care, to describe the treatment of children with leukemia. Under total care, a physician "treated the family as a whole, factoring in its psychosocial and economic needs", rather than focusing purely on physical health concerns. Previous researchers had dealt with concerns raised by families, because physicians emphasized patient physical health rather than the inclusion of bedside manners with the families. The practice of patient advocacy emerged to support and represent patients in this medico-legal and ethical discussion.

The 1970s were also an important time in the US for patient advocacy as the Patient Rights movement grew. As a major advocacy organization during the time, the National Welfare Rights Organization's (NWRO) materials for a patient's bill of rights influenced many additional organizations and writings, including hospital accreditation standards for the Joint Commission in 1970 and the American Hospital Association's Patient Bill of Rights in 1972. The utilization of advocates by individual patients gained momentum in the early 2000s in the US, and Australia 10 years later, and the profession is now perceived as a mainstream option to optimize outcomes in both hospital- and community-based healthcare.

Self-advocacy

See also: Patient participation and Patient and public involvement

Communication skills, information-seeking skills and problem-solving skills were found to correlate with measures of a patient's ability to advocate for themselves. Conceptualizations of the qualities have defined self-knowledge, communication skills, knowledge of rights, and leadership as components of advocacy.

A number of interventions have been tried to improve patients' effectiveness at advocating for themselves. Studies have found peer-led programs where an individual with a condition is taught interview skills were effective in improving self-advocacy. Writing interventions, where people with conditions received training and practiced writing essays advocating for themselves, were shown to improve self-advocacy.

Patient advocacy processes

At a conceptual level patient advocacy consists of three processes: valuing, apprising and interceding. Valuing consists of understanding the patient's unique attributes and desires. Apprising consists of informing the patient and advising the patient. Interceding consists of interacting with processes to ensure that the patient's unique attributes and desires are represented in these processes, and may include interceding in family interactions as well as healthcare processes.

Examples of patient advocacy include:

• Educating and walking patients through the management of their disease or chronic illnesses. The social determinants of health can vary significantly from patient to patient. It is the role of the patient advocate to cater to the patient's needs and assist with these factors, such as where to find treatment to manage their illness, assisting with healthcare access due to socioeconomic barriers, or helping find additional health services. Assistance with the management of their illnesses or disease can also include assisting with cooperative purchases of health care materials.
• Support with sourcing and navigating second opinions where patients seek input about diagnosis, treatment options and prognosis.
• Establishing a network of contacts. Examples of contacts patient advocates can assist in connecting patients to include: in the public sector (political and regulatory), in public and private health insurance, in the sector of medical service providers, with medical practitioners, and with pharmaceutical and medical research to provide patients with help in the care and management of their diseases.
• Providing emotional support in dealing with their health concerns, illnesses, or chronic conditions. According to the National Institute of Mental Health, individuals with chronic illnesses are at a higher risk of depression of than patients with other mental health conditions. When managing their illnesses, patients and survivors experience the direct effect of the consequences their disease has on their quality of life, and may also go through difficult phases of adaptation of their daily routine and lifestyle to accommodate the disease. Part of the role of patient advocates can include providing emotional support for patients or connecting them to mental health resources.
• Attending appointments with a patient. Patients can find doctor's appointments intimidating, but also difficult to understand. Issues may stem from differences in language proficiency, educational background, or background in health literacy. A patient advocate's presence can ensure that patient's concerns are highlighted and adequately addressed by physicians. Patient advocates may also be responsible for assisting with scheduling additional appointments as well.
• Assisting with health insurance and other financial aspects of healthcare. The Institute of Medicine in the United States says fragmentation of the U.S. health care delivery and financing system is a barrier to accessing care. Within the financing system, health insurance plays a significant role. According to a United Health survey, only 9% of Americans surveyed understood health insurance terms, which presents a significant issue for patients, given the importance of health insurance in terms of providing access to healthcare. The patient advocate may help with researching or choosing health insurance plans.

Nurse advocacy

The American Nurses Association (ANA) includes advocacy in its definition of nursing:

Nursing is the protection, promotion, and optimization of health and abilities, prevention of illness and injury, facilitation of healing, alleviation of suffering through the diagnosis and treatment of human response, and advocacy in the care of individuals, families, groups, communities, and populations.

Advocacy in nursing finds its theoretical basis in nursing ethics. For instance, the ANA's Code of Ethics for Nurses includes language relating to patient advocacy:

• The nurse's primary commitment is to the patient, whether an individual, family, group, or community.
• The nurse promotes, advocates for, and strives to protect the health, safety, and rights of the patient.

Several factors can lead a patient to use nurses for advocacy, including impairments in their ability to express wishes due to speech impairments or limited consciousness, lack of independence due to illiteracy, sociocultural weakness, or separation from friends or family caused by hospitalization. Nurses are more able to advocate if they are independent, professionally committed, and have self-confidence as well as having legal and professional knowledge, as well as knowing a patient's wishes. The act of patient advocacy improved nurses' sense of professional well-being and self-concept, job motivation and job satisfaction, and enhances the public image of nurses; however, advocating for a patient could have social and professional consequences.

Conflict of interest between a nurse's responsibilities to their employer and their responsibilities to the patient can be a barrier to advocacy. Additionally, a nurse is concerned about all of the patients they care for rather any individual patient. Gadow and Curtis argue that the role of patient advocacy in nursing is to facilitate a patient's informed consent through decision-making, but in mental health nursing there is a conflict between the patient's right to autonomy and nurses' legal and professional duty to protect the patient and the community from harm, since patients may experience delusions or confusion which affect their decision-making. In such instances, the nurse may engage in persuasion and negotiation in order to prevent the risk that they perceive.

Private advocacy

Main article: Health advocacy

Private advocates (also known as independent patient/health/health care advocates) often work parallel to the advocates that work for hospitals. As global healthcare systems started to become more complex, and as the role of the cost of care continues to place more of a burden on patients, a new profession of private professional advocacy began to take root in the mid-2000s. At that time, two organizations were founded to support the work of these new private practitioners, professional patient advocates. The National Association of Healthcare Advocacy Consultants was started to provide broad support for advocacy. The Alliance of Professional Health Advocates was started to support the business of being a private advocate. Some regions require that those detained for the treatment of mental health disorders are given access to independent mental health advocates who are not involved in the patient's treatment.

Proponents of private advocacy, such as Australian advocate Dorothy Kamaker and L. Bradley Schwartz, have noted that the patient advocates employed by healthcare facilities frequently have an inherent conflict of interest in situations where the needs of an individual patient are at odds with the corporate interests of an advocate's employer. Kamaker argues that hiring a private advocate eliminates this conflict because the private advocate "…has only one master and very clear priorities."

Kamaker founded patientadvocates.com.au in 2013 and, in partnership with Alicia Dunn, followed with disabilityhealthsupport.com.au in 2021 when research revealed that vulnerable groups achieved sub-optimal outcomes and encountered barriers and prejudice in the mainstream health and hospital systems in Australia. "Based on the limited data available, we know that the overall health of people with disabilities is much worse than that of the general population", with "people with disabilities rarely identified as a priority population group in public health policy and practice". Patients supported by advocates have been shown to experience fewer treatment errors and require fewer readmissions post discharge. In Australia there has been some movement by private health insurers to engage private patient advocates to reduce costs, improve outcomes and expedite return to work for employees.

Schwartz is the founder and president of GNANOW.org, where he states, "Everyone employed by a health care company is limited to what they can accomplish for patients and families. Hospital-employed patient advocates, navigators, social workers, and discharge planners are no different. They became health care professionals because they are passionate about helping people. But they have heavy caseloads and many work long hours with limited resources. Independent Patient Advocates work one-on-one with patients and loved ones to explore options, improve communication, and coordinate with overworked hospital staff. In fact, many Independent Patient Advocates used to work for hospitals and health care companies before they decided to work directly for patients."

Patient advocacy organizations

See also: Health policy, Health advocacy, and Patient participation § Formation of health policy as stakeholders

Patient advocacy organizations, PAO, or patient advocacy groups are organizations that exist to represent the interests of people with a particular disease. Patient advocacy organizations may fund research and influence national health policy through lobbying. Examples in the US include the American Cancer Society, American Heart Association, and National Organization for Rare Disorders.

Some patient advocacy groups receive donations from pharmaceutical companies. In the US in 2015, 14 companies donated $116 million to patient advocacy groups. A database identifying more than 1,200 patient groups showed that six pharmaceutical companies contributed $1 million or more in 2015 to individual groups representing patients who use their drugs, and 594 groups in the database received donations from pharmaceutical companies. Fifteen patient groups relied on pharmaceutical companies for at least 20 percent of their revenue in the same year, and some received more than half of their revenue from pharmaceutical companies. Recipients of donations from pharmaceutical companies include the American Diabetes Association, Susan G. Komen, and the Caring Ambassadors Program.

Patient opinion leaders, also sometimes called patient advocates, are individuals who are well versed in a disease, either as patients themselves or as caretakers, and share their knowledge on the particular disease with others. Such POLs can have an influence on health care providers and may help persuade them to use evidence-based therapies or medications in the management of other patients. Identifying such people and persuading them is one goal of market access groups at pharmaceutical and medical device companies.

Organizations

Professional groups

Solace

Solace is an American professional organization where private advocates can list their business and allow consumers to book conversations with advocates directly.

Alliance of Professional Health Advocates

The Alliance of Professional Health Advocates (APHA) is an international membership organization for private, professional patient advocates, and those who are exploring the possibility of becoming private advocates. It provides business support such as legal, insurance and marketing. It also offers a public directory of member advocates called AdvoConnection. Following the 2011 death of Ken Schueler — a charter member of the APHA, described as "the Father of Private Patient Advocacy" — the organization established the H. Kenneth Schueler Patient Advocacy Compass Award. The award recognizes excellence in private practice including the use of best practices, community outreach, support of the profession and professional ethics.

Dialysis Patient Citizens

Dialysis Patient Citizens is an American patient-led, non-profit organization dedicated to improving dialysis citizens' quality of life by advocating for favorable public policy. One of DPC's goals is to provide dialysis patients with the education, access and confidence to be their own advocates. Through their grassroots advocacy campaigns, Patient Ambassador program; Washington, D.C. patient fly-ins; conference calls and briefings, DPC works to train effective advocates for dialysis-related issues. Membership is free.

National Association of Healthcare Advocacy Consultants

National Association of Healthcare Advocacy Consultants (NAHAC) is an American nonprofit organization located in Berkeley, California. Joanna Smith founded NAHAC on July 15, 2009, as a broad-based, grassroots organization for health care and patient advocacy. To that end, it is a multi-stakeholder organization, with membership open to the general public.

National Patient Advocate Foundation

The National Patient Advocate Foundation is a non-profit organization in the United States dedicated to "...improving access to, and reimbursement for, high-quality healthcare through regulatory and legislative reform at the state and federal levels." The National Patient Advocate Foundation was founded simultaneously with the non-profit Patient Advocate Foundation, "...which provides professional case management services to Americans with chronic, life-threatening and debilitating illnesses."

Patient Advocates Australia

Patient Advocates Australia, founded by Dorothy Kamaker, is a support option for consumers of aged, health and disability care in Australia. For the elderly, an emerging need has arisen for patient advocacy in residential aged facilities. The Aged Care Royal Commission Report published in 2021 has made recommendations regarding a need for vigilant advocacy for residents of nursing homes to protect them against rampant abuse and neglect, with one submission calling for the routine provision of independent patient advocates. For the disabled, funding for support to overcome healthcare barriers is available through the National Disability Insurance Scheme.

Greater National Advocates (GNA)

Greater National Advocates is a non-profit organization with the goal of raising Americans' awareness of the lifesaving benefits of independent patient advocacy and to provide patients and loved ones with immediate online access to a trusted network of qualified practitioners. GNA uses fact-based media to spread awareness and steer patients and their loved ones to GNANOW.org where they can learn more and find the professional support they need.

Center for Patient Partnerships

Founded in 2000, the interprofessional Center for Patient Partnerships (CPP) at University of Wisconsin–Madison offers a health advocacy certificate with a focus on either patient advocacy or system-level health policy advocacy. The chapter "Educating for Health Advocacy in Settings of Higher Education" in Patient Advocacy for Health Care Quality: Strategies for Achieving Patient-Centered Care describes CPP's pedagogy and curriculum.

Government agencies

United States

In the United States, state governmental units have established ombudsmen to investigate and respond to patient complaints and to provide other consumer services.

New York

In New York, the Office of Patient Advocacy within the New York State Office of Alcoholism and Substance Abuse Services (OASAS) is responsible for protecting the rights of patients in OASAS-certified programs. The office answers questions from patients and their families; provides guidance for health care professionals on topics related to patient rights, state regulations, and treatment standards, and intervenes to resolve problems that cannot be handled within treatment programs themselves.

California

In California, the Office of the Patient Advocate (OPA), an independent state office established in July 2000 in conjunction with the Department of Managed Health Care, is responsible for the creation and distribution of educational materials for consumers, public outreach, evaluation and ranking of health care service plans, collaboration with patient assistance programs, and policy development for government health regulation.

Such state government offices may also be responsible for intervening in disputes within the legal and insurance systems and in disciplinary actions against health care professionals. Some hospitals, health insurance companies, and other health care organizations also employ people specifically to assume the role of patient advocate. Within hospitals, the person may have the title of ombudsman or patient representative.

Isotope

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Isotope

 

Nuclear physics

The three naturally occurring isotopes of hydrogen. The fact that each nuclide has 1 proton makes them all isotopes of hydrogen: the identity of the isotope is given by the number of protons and neutrons. From left to right, the isotopes are protium (¹H) with 0 neutrons, deuterium (²H) with 1 neutron, and tritium (³H) with 2 neutrons.

Isotopes are distinct nuclear species (or nuclides) of the same chemical element. They have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), but different nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have virtually the same chemical properties, they have different atomic masses and physical properties.

The term isotope comes from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place": different isotopes of an element occupy the same place on the periodic table. It was coined by Scottish doctor and writer Margaret Todd in a 1913 suggestion to the British chemist Frederick Soddy, who popularized the term.

The number of protons within the atom's nucleus is called its atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.

For example, carbon-12, carbon-13, and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons so that the neutron numbers of these isotopes are 6, 7, and 8 respectively.

Isotope vs. nuclide

A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. Thus the terms are roughly synonymous, but the nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number greatly affects nuclear properties, but its effect on chemical properties is negligible for most elements. Even for the lightest elements, whose ratio of neutron number to atomic number varies the most between isotopes, it usually has only a small effect although it matters in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to affect biology strongly). The term isotopes (originally also isotopic elements, now sometimes isotopic nuclides) is intended to imply comparison (like synonyms or isomers). For example, the nuclides ¹²
₆C, ¹³
₆C, ¹⁴
₆C are isotopes (nuclides with the same atomic number but different mass numbers), but ⁴⁰
₁₈Ar, ⁴⁰
₁₉K, ⁴⁰
₂₀Ca are isobars (nuclides with the same mass number). As the older and better-known term, isotope is however still used in some contexts where nuclide might be more appropriate, such as in nuclear technology and nuclear medicine.

Notation

An explanation of the superscripts and subscripts seen in AZE notation.

An isotope/nuclide is specified by the name of the element (this indicates the atomic number) followed by a hyphen and the mass number (e.g. helium-3, helium-4, carbon-12, carbon-14, uranium-235 and uranium-239). When a chemical symbol is used, e.g. "C" for carbon, standard notation (also known as "AZE notation" as it is written ^A_ZE where A is the mass number, Z the atomic number, and E the element name) is to indicate the mass number (number of nucleons) with a superscript at the upper left of the chemical symbol and to indicate the atomic number with a subscript at the lower left (e.g. ³
₂He, ⁴
₂He, ¹²
₆C, ¹⁴
₆C, ²³⁵
₉₂U, and ²³⁹
₉₂U). Because the atomic number is already fixed by the element symbol, it is common to state only the mass number in the superscript and leave out the atomic number subscript (e.g. ³He, ⁴He, ¹²C, ¹⁴C, ²³⁵U, and ²³⁹U). The letter m (for metastable) is appended after the mass number to indicate a nuclear isomer, a metastable or energetically excited nuclear state (as opposed to the lowest-energy ground state), for example ^180m
₇₃Ta (tantalum-180m); a number can be appended to it to distinguish different metastable states, though this is rare in practice.

The common pronunciation of the AZE notation is different from how it is written: ⁴
₂He is commonly pronounced helium-four instead of four-two-helium, and ²³⁵
₉₂U uranium two-thirty-five (American English) or uranium-two-three-five (British) instead of 235-92-uranium or 235-uranium. This is not an error but the original spoken usage for isotope names, originating before AZE notation became established.

Radioactive, primordial, and stable isotopes

Some isotopes/nuclides are radioactive, and are therefore called radioisotopes or radionuclides, whereas others have never been observed to decay radioactively and are called stable isotopes or stable nuclides. For example, ¹⁴C is a radioactive form of carbon, while ¹²C and ¹³C are stable isotopes. There are about 339 naturally occurring nuclides on Earth, of which 286 are primordial nuclides, meaning that they have existed since the Solar System's formation.

Primordial nuclides include 35 nuclides with very long half-lives (over 100 million years) and 251 that are considered "stable nuclides", as they have not been observed to decay. In most cases, if an element has stable isotopes, those isotopes predominate in the elemental abundance found on Earth and in the Solar System. However, in the cases of three elements (tellurium, indium, and rhenium) the most abundant isotope found in nature is actually one (or two) extremely long-lived radioisotope(s) of the element, despite these elements having one or more stable isotopes.

Theory predicts that many apparently "stable" nuclides are radioactive, with extremely long half-lives (discounting the possibility of proton decay, which would make all nuclides ultimately unstable). Some stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, and so these isotopes are said to be "observationally stable". The predicted half-lives for these nuclides often greatly exceed the estimated age of the universe, and in fact, there are also 31 known radionuclides (see primordial nuclide) with half-lives longer than the age of the universe.

The total of all known nuclides, of which most have been created only artificially, is several thousand, of which 987 are stable or have a half-life longer than one hour; see List of nuclides.

History

Radioactive isotopes

The existence of isotopes was first suggested in 1913 by the radiochemist Frederick Soddy, based on studies of radioactive decay chains that indicated about 40 different species referred to as radioelements (i.e. radioactive elements) between uranium and lead, although the periodic table only allowed for 11 elements between lead and uranium inclusive.

Several attempts to separate these new radioelements chemically had failed. For example, Soddy had shown in 1910 that mesothorium (later shown to be ²²⁸Ra), radium (²²⁶Ra, the longest-lived isotope), and thorium X (²²⁴Ra) are impossible to separate. Attempts to place the radioelements in the periodic table led Soddy and Kazimierz Fajans independently to propose their radioactive displacement law in 1913, to the effect that alpha decay produced an element two places to the left in the periodic table, whereas beta decay emission produced an element one place to the right. Soddy recognized that emission of an alpha particle followed by two beta particles led to the formation of an element chemically identical to the initial element but with a mass four units lighter and with different radioactive properties.

Soddy proposed that several types of atoms (differing in radioactive properties) could occupy the same place in the table. For example, the alpha-decay of uranium-235 forms thorium-231, whereas the beta decay of actinium-230 forms thorium-230. The term "isotope", Greek for "at the same place", was suggested to Soddy by Margaret Todd, a Scottish physician and family friend, during a conversation in which he explained his ideas to her. He received the 1921 Nobel Prize in Chemistry in part for his work on isotopes.

In the bottom right corner of J. J. Thomson's photographic plate are the separate impact marks for the two isotopes of neon: neon-20 and neon-22.

In 1914 T. W. Richards found variations between the atomic weight of lead from different mineral sources, attributable to radiogenic variations in isotopic composition; the natural radioactive series ending with three different isotopes of lead.

Stable isotopes

The first evidence for multiple isotopes of a stable (non-radioactive) element was found by J. J. Thomson in 1912 as part of his exploration into the composition of canal rays (positive ions). Thomson channelled streams of neon ions through parallel magnetic and electric fields, measured their deflection by placing a photographic plate in their path, and computed their mass to charge ratio using a method that became known as the Thomson's parabola method. Each stream created a glowing patch on the plate at the point it struck. Thomson observed two separate parabolic patches of light on the photographic plate (see image), which suggested two species of nuclei with different mass-to-charge ratios. He wrote "There can, therefore, I think, be little doubt that what has been called neon is not a simple gas but a mixture of two gases, one of which has an atomic weight about 20 and the other about 22. The parabola due to the heavier gas is always much fainter than that due to the lighter, so that probably the heavier gas forms only a small percentage of the mixture."

F. W. Aston subsequently discovered multiple stable isotopes for numerous elements using a mass spectrograph, related to Thomson's method. In 1919 Aston studied neon with sufficient resolution to show that the two isotopic masses are very close to the integers 20 and 22, and that neither is equal to the known molar mass (20.2) of neon gas. This is an example of Aston's whole number rule for isotopic masses, now known to be exceptionless, which states that large deviations of elemental molar masses from integers are due to the fact that the element is a mixture of isotopes. Aston similarly showed in 1920 that the molar mass of chlorine (35.45) is a weighted average of the almost integral masses for the two isotopes ³⁵Cl and ³⁷Cl.

Neutrons

After the discovery of the neutron by James Chadwick in 1932, the ultimate root cause for the existence of isotopes was clarified, that is, the nuclei of different isotopes for a given element have different numbers of neutrons, albeit having the same number of protons.

Variation in properties between isotopes

Chemical and molecular properties

A neutral atom has the same number of electrons as protons. Thus different isotopes of a given element all have the same number of electrons and share a similar electronic structure. Because the chemical behaviour of an atom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behaviour.

The main exception to this is the kinetic isotope effect: due to their larger masses, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element. This is most pronounced by far for protium (¹
H), deuterium (²
H), and tritium (³
H), because deuterium has twice the mass of protium and tritium has three times the mass of protium. These mass differences also affect the behavior of their respective chemical bonds, by changing the center of gravity (reduced mass) of the atomic systems. However, for heavier elements, the relative mass difference between isotopes is much less so that the mass-difference effects on chemistry are usually negligible. (Heavy elements also have relatively more neutrons than lighter elements, so the ratio of the nuclear mass to the collective electronic mass is slightly greater.) There is also an equilibrium isotope effect.

Isotope half-lives. Z = number of protons. N = number of neutrons. The plot for stable isotopes diverges from the line Z = N as the element number Z becomes larger

Similarly, two molecules that differ only in the isotopes of their atoms (isotopologues) have identical electronic structures, and therefore almost indistinguishable physical and chemical properties (again with deuterium and tritium being the primary exceptions). The vibrational modes of a molecule are determined by its shape and by the masses of its constituent atoms; so different isotopologues have different sets of vibrational modes. Because vibrational modes allow a molecule to absorb photons of corresponding energies, isotopologues have different optical properties in the infrared range.

Nuclear properties and stability

See also: Stable nuclide, Stable isotope ratio, List of nuclides, and List of elements by stability of isotopes

Atomic nuclei consist of protons and neutrons bound together by the residual strong force. Because protons are positively charged, they repel each other. Neutrons, which are electrically neutral, stabilize the nucleus in two ways. Their copresence pushes protons slightly apart, reducing the electrostatic repulsion between the protons, and they exert an attractive nuclear force on each other and on protons. For this reason, one or more neutrons are necessary for two or more protons to bind into a nucleus. As the number of protons increases, so does the ratio of neutrons to protons necessary to ensure a stable nucleus (see graph at right). For example, although the neutron:proton ratio of ³
₂He is 1:2, the neutron:proton ratio of ²³⁸
₉₂U is greater than 3:2. A number of lighter elements have stable nuclides with the ratio 1:1 (Z = N). The nuclide ⁴⁰
₂₀Ca (calcium-40) is observationally the heaviest stable nuclide with the same number of neutrons and protons. All stable nuclides heavier than calcium-40 contain more neutrons than protons.

Numbers of isotopes per element

Of the 80 elements with a stable isotope, the largest number of stable isotopes observed for any element is ten (for the element tin). No element has nine or eight stable isotopes. Five elements have seven stable isotopes, seven have six stable isotopes, eleven have five stable isotopes, nine have four stable isotopes, five have three stable isotopes, 16 have two stable isotopes (counting ^180m
₇₃Ta as stable), and 26 elements have only a single stable isotope (of these, 19 are so-called mononuclidic elements, having a single primordial stable isotope that dominates and fixes the atomic weight of the natural element to high precision; two radioactive mononuclidic elements occur as well). In total, there are 251 nuclides that have not been observed to decay. For the 80 elements that have one or more stable isotopes, the average number of stable isotopes is 251/80 ≈ 3.14 isotopes per element.

Even and odd nucleon numbers

Main article: Even and odd atomic nuclei

Even/odd Z, N (¹
H as OE)

p, n	EE	OO	EO	OE	Total
Stable	145	5	53	48	251
Long-lived	23	4	3	5	35
All primordial	168	9	56	53	286

The proton:neutron ratio is not the only factor affecting nuclear stability. It depends also on evenness or oddness of its atomic number Z, neutron number N and, consequently, of their sum, the mass number A. Oddness of both Z and N tends to lower the nuclear binding energy, making odd nuclei, generally, less stable. This remarkable difference of nuclear binding energy between neighbouring nuclei, especially of odd-A isobars, has important consequences: unstable isotopes with a nonoptimal number of neutrons or protons decay by beta decay (including positron emission), electron capture, or other less common decay modes such as spontaneous fission and cluster decay.

Most stable nuclides are even-proton-even-neutron, where all numbers Z, N, and A are even. The odd-A stable nuclides are divided (roughly evenly) into odd-proton-even-neutron, and even-proton-odd-neutron nuclides. Stable odd-proton-odd-neutron nuclides are the least common.

Even atomic number

The 146 even-proton, even-neutron (EE) nuclides comprise ~58% of all stable nuclides and all have spin 0 because of pairing. There are also 24 primordial long-lived even-even nuclides. As a result, each of the 41 even-numbered elements from 2 to 82 has at least one stable isotope, and most of these elements have several primordial isotopes. Half of these even-numbered elements have six or more stable isotopes. The extreme stability of helium-4 due to a double pairing of 2 protons and 2 neutrons prevents any nuclides containing five (⁵
₂He, ⁵
₃Li) or eight (⁸
₄Be) nucleons from existing long enough to serve as platforms for the buildup of heavier elements via nuclear fusion in stars (see triple alpha process).

Even-odd long-lived

	Decay	Half-life
113 48Cd	beta	7.7×1015 a
147 62Sm	alpha	1.06×1011 a
235 92U	alpha	7.04×108 a

Only five stable nuclides contain both an odd number of protons and an odd number of neutrons. The first four "odd-odd" nuclides occur in low mass nuclides, for which changing a proton to a neutron or vice versa would lead to a very lopsided proton-neutron ratio (²
₁H, ⁶
₃Li, ¹⁰
₅B, and ¹⁴
₇N; spins 1, 1, 3, 1). The only other entirely "stable" odd-odd nuclide, ^180m
₇₃Ta (spin 9), is thought to be the rarest of the 251 stable nuclides, and is the only primordial nuclear isomer, which has not yet been observed to decay despite experimental attempts.

Many odd-odd radionuclides (such as the ground state of tantalum-180) with comparatively short half-lives are known. Usually, they beta-decay to their nearby even-even isobars that have paired protons and paired neutrons. Of the nine primordial odd-odd nuclides (five stable and four radioactive with long half-lives), only ¹⁴
₇N is the most common isotope of a common element. This is the case because it is a part of the CNO cycle. The nuclides ⁶
₃Li and ¹⁰
₅B are minority isotopes of elements that are themselves rare compared to other light elements, whereas the other six isotopes make up only a tiny percentage of the natural abundance of their elements.

Odd atomic number

53 stable nuclides have an even number of protons and an odd number of neutrons. They are a minority in comparison to the even-even isotopes, which are about 3 times as numerous. Among the 41 even-Z elements that have a stable nuclide, only two elements (argon and cerium) have no even-odd stable nuclides. One element (tin) has three. There are 24 elements that have one even-odd nuclide and 13 that have two odd-even nuclides. Of 35 primordial radionuclides there exist four even-odd nuclides (see table at right), including the fissile ²³⁵
₉₂U. Because of their odd neutron numbers, the even-odd nuclides tend to have large neutron capture cross-sections, due to the energy that results from neutron-pairing effects. These stable even-proton odd-neutron nuclides tend to be uncommon by abundance in nature, generally because, to form and enter into primordial abundance, they must have escaped capturing neutrons to form yet other stable even-even isotopes, during both the s-process and r-process of neutron capture, during nucleosynthesis in stars. For this reason, only ¹⁹⁵
₇₈Pt and ⁹
₄Be are the most naturally abundant isotopes of their element.

48 stable odd-proton-even-neutron nuclides, stabilized by their paired neutrons, form most of the stable isotopes of the odd-numbered elements; the very few odd-proton-odd-neutron nuclides comprise the others. There are 41 odd-numbered elements with Z = 1 through 81, of which 39 have stable isotopes (technetium (
₄₃Tc) and promethium (
₆₁Pm) have no stable isotopes). Of these 39 odd Z elements, 30 elements (including hydrogen-1 where 0 neutrons is even) have one stable odd-even isotope, and nine elements: chlorine (
₁₇Cl), potassium (
₁₉K), copper (
₂₉Cu), gallium (
₃₁Ga), bromine (
₃₅Br), silver (
₄₇Ag), antimony (
₅₁Sb), iridium (
₇₇Ir), and thallium (
₈₁Tl), have two odd-even stable isotopes each. This makes a total 30 + 2(9) = 48 stable odd-even isotopes.

There are also five primordial long-lived radioactive odd-even isotopes, ⁸⁷
₃₇Rb, ¹¹⁵
₄₉In, ¹⁸⁷
₇₅Re, ¹⁵¹
₆₃Eu, and ²⁰⁹
₈₃Bi. The last two were only recently found to decay, with half-lives greater than 10¹⁸ years.

Odd neutron number

Neutron number parity (¹
H as even)

N	Even	Odd
Stable	193	58
Long-lived	28	7
All primordial	221	65

Actinides with odd neutron number are generally fissile (with thermal neutrons), whereas those with even neutron number are generally not, though they are fissionable with fast neutrons. All observationally stable odd-odd nuclides have nonzero integer spin. This is because the single unpaired neutron and unpaired proton have a larger nuclear force attraction to each other if their spins are aligned (producing a total spin of at least 1 unit), instead of anti-aligned. See deuterium for the simplest case of this nuclear behavior.

Only ¹⁹⁵
₇₈Pt, ⁹
₄Be, and ¹⁴
₇N have odd neutron number and are the most naturally abundant isotope of their element.

Occurrence in nature

See also: Abundance of the chemical elements

Elements are composed either of one nuclide (mononuclidic elements), or of more than one naturally occurring isotopes. The unstable (radioactive) isotopes are either primordial or postprimordial. Primordial isotopes were a product of stellar nucleosynthesis or another type of nucleosynthesis such as cosmic ray spallation, and have persisted down to the present because their rate of decay is very slow (e.g. uranium-238 and potassium-40). Post-primordial isotopes were created by cosmic ray bombardment as cosmogenic nuclides (e.g., tritium, carbon-14), or by the decay of a radioactive primordial isotope to a radioactive radiogenic nuclide daughter (e.g. uranium to radium). A few isotopes are naturally synthesized as nucleogenic nuclides, by some other natural nuclear reaction, such as when neutrons from natural nuclear fission are absorbed by another atom.

As discussed above, only 80 elements have any stable isotopes, and 26 of these have only one stable isotope. Thus, about two-thirds of stable elements occur naturally on Earth in multiple stable isotopes, with the largest number of stable isotopes for an element being ten, for tin (
₅₀Sn). There are about 94 elements found naturally on Earth (up to plutonium inclusive), though some are detected only in very tiny amounts, such as plutonium-244. Scientists estimate that the elements that occur naturally on Earth (some only as radioisotopes) occur as 339 isotopes (nuclides) in total. Only 251 of these naturally occurring nuclides are stable, in the sense of never having been observed to decay as of the present time. An additional 35 primordial nuclides (to a total of 286 primordial nuclides), are radioactive with known half-lives, but have half-lives longer than 100 million years, allowing them to exist from the beginning of the Solar System. See list of nuclides for details.

All the known stable nuclides occur naturally on Earth; the other naturally occurring nuclides are radioactive but occur on Earth due to their relatively long half-lives, or else due to other means of ongoing natural production. These include the afore-mentioned cosmogenic nuclides, the nucleogenic nuclides, and any radiogenic nuclides formed by ongoing decay of a primordial radioactive nuclide, such as radon and radium from uranium.

An additional ~3000 radioactive nuclides not found in nature have been created in nuclear reactors and in particle accelerators. Many short-lived nuclides not found naturally on Earth have also been observed by spectroscopic analysis, being naturally created in stars or supernovae. An example is aluminium-26, which is not naturally found on Earth but is found in abundance on an astronomical scale.

The tabulated atomic masses of elements are averages that account for the presence of multiple isotopes with different masses. Before the discovery of isotopes, empirically determined noninteger values of relative atomic mass confounded scientists. For example, a sample of chlorine contains 75.8% chlorine-35 and 24.2% chlorine-37, giving an average atomic mass of 35.5 daltons.

According to generally accepted cosmology theory, only isotopes of hydrogen and helium, traces of some isotopes of lithium and beryllium, and perhaps some boron, were created at the Big Bang, while all other nuclides were synthesized later, in stars and supernovae, and in interactions between energetic particles such as cosmic rays, and previously produced nuclides. (See nucleosynthesis for details of the various processes thought responsible for isotope production.) The respective abundances of isotopes on Earth result from the quantities formed by these processes, their spread through the galaxy, and the rates of decay for isotopes that are unstable. After the initial coalescence of the Solar System, isotopes were redistributed according to mass, and the isotopic composition of elements varies slightly from planet to planet. This sometimes makes it possible to trace the origin of meteorites.

Atomic mass of isotopes

The atomic mass of an isotope (nuclide) is determined mainly by its atomic mass number (i.e. number of nucleons in its nucleus). Small corrections are due to the binding energy of the nucleus (see mass defect), the slight difference in mass between proton and neutron, and the mass of the electrons associated with the atom, the latter because the electron:nucleon ratio differs among isotopes.

The mass number is a dimensionless quantity. The atomic mass, on the other hand, is measured using the dalton (symbol Da), which is defined in terms of the mass of the carbon-12 atom. It is also called the unified atomic mass unit (symbol u).

The atomic masses of naturally occurring isotopes of an element determine the standard atomic weight of the element. When the element contains N isotopes, the expression below is applied for the average atomic mass ${\displaystyle {\overline{m}}_a}$:

${\displaystyle {\overline{m}}_a=m_1{x}_1+m_2{x}_2+...+m_N{x}_N}$

where m₁, m₂, ..., m_N are the atomic masses of each individual isotope, and x₁, ..., x_N are the relative abundances of these isotopes.

Applications of isotopes

Purification of isotopes

Main article: isotope separation

Several applications exist that capitalize on the properties of the various isotopes of a given element. Isotope separation is a significant technological challenge, particularly with heavy elements such as uranium or plutonium. Lighter elements such as lithium, carbon, nitrogen, and oxygen are commonly separated by gas diffusion of their compounds such as CO and NO. The separation of hydrogen and deuterium is unusual because it is based on chemical rather than physical properties, for example in the Girdler sulfide process. Uranium isotopes have been separated in bulk by gas diffusion, gas centrifugation, laser ionization separation, and (in the Manhattan Project) by a type of production mass spectrometry.

Use of chemical and biological properties

Main articles: isotope geochemistry, cosmochemistry, and paleoclimatology

• Isotope analysis is the determination of isotopic signature, the relative abundances of isotopes of a given element in a particular sample. Isotope analysis is frequently done by isotope ratio mass spectrometry. For biogenic substances in particular, significant variations of isotopes of C, N, and O can occur. Analysis of such variations has a wide range of applications, such as the detection of adulteration in food products or the geographic origins of products using isoscapes. The identification of certain meteorites as having originated on Mars is based in part upon the isotopic signature of trace gases contained in them.
• Isotopic substitution can be used to determine the mechanism of a chemical reaction via the kinetic isotope effect.
• Another common application is isotopic labeling, the use of unusual isotopes as tracers or markers in chemical reactions. Normally, atoms of a given element are indistinguishable from each other. However, by using isotopes of different masses, even different nonradioactive stable isotopes can be distinguished by mass spectrometry or infrared spectroscopy. For example, in 'stable isotope labeling with amino acids in cell culture (SILAC)' stable isotopes are used to quantify proteins. If radioactive isotopes are used, they can be detected by the radiation they emit (this is called radioisotopic labeling).
• Isotopes are commonly used to determine the concentration of various elements or substances using the isotope dilution method, whereby known amounts of isotopically substituted compounds are mixed with the samples and the isotopic signatures of the resulting mixtures are determined with mass spectrometry.

Use of nuclear properties

• A technique similar to radioisotopic labeling is radiometric dating: using the known half-life of an unstable element, one can calculate the amount of time that has elapsed since a known concentration of isotope existed. The most widely known example is radiocarbon dating used to determine the age of carbonaceous materials.
• Several forms of spectroscopy rely on the unique nuclear properties of specific isotopes, both radioactive and stable. For example, nuclear magnetic resonance (NMR) spectroscopy can be used only for isotopes with a nonzero nuclear spin. The most common nuclides used with NMR spectroscopy are ¹H, ²D, ¹⁵N, ¹³C, and ³¹P.
• Mössbauer spectroscopy also relies on the nuclear transitions of specific isotopes, such as ⁵⁷Fe.
• Radionuclides also have important uses. Nuclear power and nuclear weapons development require relatively large quantities of specific isotopes. Nuclear medicine and radiation oncology utilize radioisotopes respectively for medical diagnosis and treatment.