Age discrimination in the United States

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

In the United States, all states have passed laws that restrict age discrimination, and age discrimination is restricted under federal laws such as the Age Discrimination in Employment Act of 1967 (ADEA).

Credit transactions

The Equal Credit Opportunity Act (ECOA) is a United States law (codified at 15 U.S.C. § 1691 et seq.), enacted 28 October 1974, that makes it unlawful for any creditor to discriminate against any applicant, with respect to any aspect of a credit transaction, on the basis of (among other things) age, provided the applicant has the capacity to contract.

Elected office

Some U.S. political offices have qualifications that discriminate on the basis of age. For example, pursuant to the Constitution of the United States the President of the United States must be at least 35 years old; a United States senator must be at least 30; and a member of the United States House of Representatives must be at least age 25.

Employment

The Age Discrimination in Employment Act of 1967 (ADEA) (29 U.S.C. § 621 to 29 U.S.C. § 634) is a federal law that provides certain employment protections to workers who are over the age of forty, who work for an employer who has twenty or more employees. For protected workers, the ADEA prohibits discrimination at all levels of employment, from recruitment and hiring, through the employment relationship, and through decisions for layoffs or termination of the employment relationship. An age limit may only be legally specified for protected workers in the circumstance where age has been shown to be a "bona fide occupational qualification [BFOQ] reasonably necessary to the normal operation of the particular business" (see 29 U.S.C. § 623(f)(1)). In practice, BFOQs for age are limited to the obvious (hiring a young actor to play a young character in a movie), when a job is physically demanding (police, firefighters, military service), or when public safety is a concern (for example, in the case of age limits for pilots, truck drivers, and bus drivers).

Some states like New York and New Jersey including District of Columbia have laws that protect younger workers from reverse age discrimination, a practice not prohibited under the ADEA. In these jurisdictions, employers are legally prohibited from discriminating against workers 18 and older for their age unless a bona fide occupational qualification exists (i.e., employers may require bartenders to be at least 21 to comply with the legal drinking age).

In 1968, the EEOC declared age restrictions on flight attendants' employment to be illegal sex discrimination under Title VII of the Civil Rights Act of 1964.

Mandatory retirement

Mandatory retirement due to age is generally unlawful in the United States, except in certain industries and occupations that are regulated by law, and are often part of the government (such as military service and federal police agencies, such as the Federal Bureau of Investigation). Minnesota has statutorily established mandatory retirement for all judges at age 70 (more precisely, at the end of the month a judge reaches that age). The Minnesota Legislature has had the constitutional right to set judicial retirement ages since 1956, but did not do so until 1973, setting the age at 70. The Federal Age Discrimination in Employment Act, which became law in 1986, ended mandatory age-related retirement at age 70 for many jobs, not including the Minnesota judiciary; another exception was all postsecondary institutions (colleges, etc.) This exception ended on December 31, 1993. The Fair Treatment for Experienced Pilots Act (Public Law 110-135) went into effect on December 13, 2007, raising the mandatory retirement age for pilots to 65 from the previous 60.

Minimum wage

In 1986, the Fair Labor Standards Act was amended to allow the United States Secretary of Labor to provide special certificates to allow an employer to pay less than the minimum wage to individuals whose earning or productive capacity is impaired by age, physical or mental deficiency, or injury. These employees must still be paid wages that are related to the individual's productivity and commensurate with those paid to similarly located and employed nonhandicapped workers.

Federal minimum wage laws allow for employers to pay lower wages to young workers. Many state and local minimum wage laws mirror such an age-based, tiered minimum wage.

Employment of minors

In the United States, a person must generally be at least 14 years old to seek a job, and workers face additional restrictions on their work activities until they reach age 16. Additional age restrictions for workers vary by state. For example, many states require workers under 18 years of age to have work permits and not fulfill occupations deemed hazardous.

Notable case law

In Western Air Lines, Inc v Criswell 472 US 400 (1985) the United States Supreme Court held it was lawful to require airline pilots to retire at 60, because the Federal Aviation Authority forbid using pilots over 60 in aviation. But the Court held that refusing to employ flight engineers over that age was unjustified as there were no such FAA requirements. (Note that The Fair Treatment for Experienced Pilots Act (Public Law 110-135) went into effect on December 13, 2007, raising the mandatory retirement age for pilots to 65 from the previous 60.)

DeMarco v. Holy Cross High School 4 F.3d 166 (2nd Cir. 1993) was an employment discrimination case brought under the ADEA (Age Discrimination in Employment Act of 1967). The appellant, Guy DeMarco, was released from employment prior to his eligibility for tenure at the age of forty-nine. Holy Cross High School argued that it was not subject to ADEA laws, and if it were that this case against it was in violation of the Free Exercise Clause and the Establishment Clause of the First Amendment. The defendant also argued that the plaintiff failed to utilize the administrative remedies available. The court noted that other anti-discrimination statutes were held to be applicable to religious organizations, with the exception of statutes that prohibited discrimination based on religious belief. Since statutes prohibiting discrimination by race, gender and national origin were already found applicable to religious organizations, it was logical (and a reasonable interpretation of the legislative history) to extend the prohibition against age discrimination to religious organizations as well. The decision of the district court was reversed and the case remanded for further proceedings.

Hazen Paper Co. v. Biggins 507 U.S. 604 (1993) was a United States Supreme Court case in which the court held that a disparate treatment claim cannot succeed unless the employee's protected trait had a determinative influence on the employer's decisionmaking. This case concerned how Hazen Paper fired Biggins, 62, a few weeks before his service would have reached the required number of years for his pension to vest. Biggins sued Hazen Paper alleging a violation of the Age Discrimination in Employment Act of 1967.

In Kimel v. Florida Bd. of Regents, 528 U.S. 62 (2000), the United States Supreme Court held that state employees cannot sue states for monetary damages under the Age Discrimination in Employment Act of 1967 in federal court. The EEOC may still enforce the ADEA against states, and state employees may still sue state officials for declaratory and injunctive relief.

In Gomez-Perez v. Potter (2008), the United States Supreme Court allowed federal workers who experience retaliation as a result of reporting age discrimination under the law to sue for damages.

The United States Supreme Court, in Meacham v. Knolls Atomic Power Lab, 554 U.S. 84 (2008), held that the employer, not the employee, bears the burden of proving that a layoff or other action that hurts older workers more than others was based not on age but on some other “reasonable factor.”

In 2009, the United States Supreme Court issued its opinion on Gross v. FBL Financial Services, Inc.. In a 5–4 opinion, the Court ruled that private-sector plaintiffs must prove that age was the "but for" cause of the adverse employment action they are suing over. That is, the plaintiff must prove that age discrimination was the determining reason for the adverse employment action (e.g. the action would not have been taken 'but for' the plaintiff's age). However, the Supreme Court's opinion did not explicitly mention public-sector workers. A later opinion, University of Texas Southwestern Medical Center v. Nassar (2013) applied the same 'but for' standard to retaliation claims.

In September 2016, California passed state bill AB-1687, an anti-ageism law taking effect on 1 January 2017, requiring "commercial online entertainment employment" services that allow paid subscribers to submit information and resumes (such as IMDB Pro), to honor requests to have their ages and birthdays removed. The bill was supported by SAG-AFTRA's former and current presidents Ken Howard and Gabrielle Carteris, who felt that the law would help to reduce ageism in the entertainment industry. On 23 February 2017, U.S. District Judge Vince Girdhari Chhabria issued a stay on the bill pending a further trial, claiming that it was "difficult to imagine how AB 1687 could not violate the First Amendment" because it inhibited the public consumption of factual information. In February 2018, Girdhari ruled that the law was unconstitutional, arguing that the state of California "[had] not shown that partially eliminating one source of age-related information will appreciably diminish the amount of age discrimination occurring in the entertainment industry." The ruling was criticized by SAG-AFTRA, alleging that the court "incorrectly concluded there were no material disputed factual issues, while precluding the parties from acquiring additional evidence or permitting the case to go to trial". The ruling was eventually appealed, but the Ninth Circuit Court of Appeals upheld it in 2020.

Babb v. Wilkie, No. 18-882, , 589 U.S. ___ (2020), is a case of the United States Supreme Court in which the justices considered the scope of protections for federal employees in the Age Discrimination in Employment Act of 1967. Specifically, the Court ruled that plaintiffs only need to prove that age was a motivating factor in the decision in order to sue. However, establishing but for causation is still necessary in determining the appropriate remedy. If a plaintiff can establish that the age was the determining factor in the employment outcome, they may be entitled to compensatory damages or other relief relating to the end result of the employment decision.

Our Lady of Guadalupe School v. Morrissey-Berru, 591 U.S. ___ (2020), is a United States Supreme Court case involving the ministerial exception of federal employment discrimination laws. The case extends from the Supreme Court's prior decision in Hosanna-Tabor Evangelical Lutheran Church & School v. Equal Employment Opportunity Commission (2012) which created the ministerial exception based on the Establishment and Free Exercise Clauses of the United States Constitution, asserting that federal discrimination laws cannot be applied to leaders of religious organizations. The Supreme Court case Our Lady of Guadalupe School v. Morrissey-Berru, along with the consolidated St. James School v. Biel (Docket 19-348), both arose from rulings in the United States Court of Appeals for the Ninth Circuit that found that federal discrimination laws do apply to others within a religious organization that serve an important religious function but lack the title or training to be considered a religious leader under Hosanna-Tabor. One of those rulings in the United States Court of Appeals for the Ninth Circuit was the ruling in Morrissey-Berru v. Our Lady of Guadalupe School, in 2019, in which the United States Court of Appeals for the Ninth Circuit allowed a Catholic elementary school teacher's age discrimination suit to move forward. The religious organization challenged that ruling on the basis of Hosanna-Tabor. The Supreme Court ruled in a 7–2 decision called Our Lady of Guadalupe School v. Morrissey-Berru on July 8, 2020 that reversed the Ninth Circuit's ruling, affirming that the principles of Hosanna-Tabor, that a person can be serving an important religious function even if not holding the title or training of a religious leader, satisfied the ministerial exception in employment discrimination.rally funded programs

The Older Americans Amendments of 1975 (Pub.L. 94–135) is an Act of the 94th U.S. Congress amending the Older Americans Act of 1965. It prohibits discrimination based on age in programs or activities that receive federal financial assistance, for instance, financial assistance to schools and colleges, provided by the U.S. Department of Education.

Hate crimes

The District of Columbia and twelve states (California, Florida, Iowa, Hawaii, Kansas, Louisiana, Maine, Minnesota, Nebraska, New Mexico, New York, and Vermont) define age as a specific motivation for hate crimes.

Voting

The Twenty-sixth Amendment to the United States Constitution reads:

Section 1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.

Section 2. The Congress shall have power to enforce this article by appropriate legislation.

That amendment was ratified in 1971. Prior to that:

In 1943 and 1955 respectively, the Georgia and Kentucky legislatures approved measures to lower the voting age to 18.

On June 22, 1970, President Richard Nixon signed an extension of the Voting Rights Act of 1965 that required the voting age to be 18 in all federal, state, and local elections. In his statement on signing the extension, Nixon said:

Despite my misgivings about the constitutionality of this one provision, I have signed the bill. I have directed the Attorney General to cooperate fully in expediting a swift court test of the constitutionality of the 18-year-old provision.

Subsequently, Oregon and Texas challenged the law in court, and the case came before the Supreme Court in 1970 as Oregon v. Mitchell. By this time, four states had a minimum voting age below 21: Georgia, Kentucky, Alaska and Hawaii. In Oregon v. Mitchell (1970), the Supreme Court considered whether the voting-age provisions Congress added to the Voting Rights Act in 1970 were constitutional. The Court struck down the provisions that established 18 as the voting age in state and local elections. However, the Court upheld the provision establishing the voting age as 18 in federal elections. The Court was deeply divided in this case, and a majority of justices did not agree on a rationale for the holding. The decision resulted in states being able to maintain 21 as the voting age in state and local elections, but being required to establish separate voter rolls so that voters between 18 and 21 years old could vote in federal elections.

Activism

The Newsboys Strike of 1899 fought ageist employment practices targeted against youth by large newspaper syndicates in the Northeast. The strikers demonstrated across the city for several days, effectively stopping circulation of the two papers, along with the news distribution for many New England cities. The strike lasted two weeks, causing Pulitzer's New York World to decrease its circulation from 360,000 papers sold per day to 125,000. Although the price of papers was not lowered, the strike was successful in forcing the World and Journal to offer full buybacks to their sellers, thus increasing the amount of money that newsies received for their work.

The American Youth Congress, or AYC, was formed in 1935 to advocate for youth rights in U.S. politics. It ended in 1940.

The AARP was founded in 1958 by Ethel Percy Andrus (a retired educator from California) and Leonard Davis (later the founder of the Colonial Penn Group of insurance companies). Its stated mission is "to empower people to choose how they live as they age". It is an influential lobbying group in the United States focusing largely on issues affecting the elderly.

The Gray Panthers was formed in 1970 by Maggie Kuhn, with a goal of eliminating mandatory retirement; they now work on many social justice issues including eliminating ageism.

Youth Liberation of Ann Arbor started in 1970 to promote youth and fight ageism.

Three O'Clock Lobby formed in 1976 to promote youth participation throughout traditionally ageist government structures in Michigan.

OWL - The Voice of Women 40+ was founded as the Older Women's League by Tish Sommers and Laurie Shields, following the White House Mini-Conference on Older Women in Des Moines, Iowa in October 1980. It advocated for women in the U.S. who were age 40 and over. In March 2017, it was reported that the national organization had decided to disband, but local chapters may continue to function under the OWL name or possibly another name.

Old Lesbians Organizing for Change was founded in 1987; the mission of the organization is to "eliminate the oppression of ageism and to stand in solidarity against all oppressions" through “[the] cooperative community of Old Lesbian feminist activists from many backgrounds working for justice and the well-being of all old lesbians.” Their initial meeting was inspired by the publication of the book Look Me in the Eye: Old Women, Aging and Ageism by Barbara Macdonald and Cynthia Rich in 1983.

Americans for a Society Free from Age Restrictions formed in 1996 to advance the civil and human rights of young people through eliminating ageist laws targeted against young people, and to help youth counter ageism in America.

The National Youth Rights Association started in 1998 to promote awareness of the legal and human rights of young people in the United States.

The Freechild Project was formed in 2001 to identify, unify and promote diverse opportunities for youth engagement in social change by fighting ageism. In 2002 the Freechild Project created an information and training initiative to provide resources to youth organizations and schools focused on youth rights.

Bioinorganic chemistry

From Wikipedia, the free encyclopedia

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

Bioinorganic chemistry is a field that examines the role of metals in biology. Bioinorganic chemistry includes the study of both natural phenomena such as the behavior of metalloproteins as well as artificially introduced metals, including those that are non-essential, in medicine and toxicology. Many biological processes such as respiration depend upon molecules that fall within the realm of inorganic chemistry. The discipline also includes the study of inorganic models or mimics that imitate the behaviour of metalloproteins.

As a mix of biochemistry and inorganic chemistry, bioinorganic chemistry is important in elucidating the implications of electron-transfer proteins, substrate bindings and activation, atom and group transfer chemistry as well as metal properties in biological chemistry. The successful development of truly interdisciplinary work is necessary to advance bioinorganic chemistry.

Composition of living organisms

About 99% of mammals' mass are the elements carbon, nitrogen, calcium, sodium, chlorine, potassium, hydrogen, phosphorus, oxygen and sulfur. The organic compounds (proteins, lipids and carbohydrates) contain the majority of the carbon and nitrogen and most of the oxygen and hydrogen is present as water. The entire collection of metal-containing biomolecules in a cell is called the metallome.

History

Paul Ehrlich used organoarsenic (“arsenicals”) for the treatment of syphilis, demonstrating the relevance of metals, or at least metalloids, to medicine, that blossomed with Rosenberg's discovery of the anti-cancer activity of cisplatin (cis-PtCl₂(NH₃)₂). The first protein ever crystallized (see James B. Sumner) was urease, later shown to contain nickel at its active site. Vitamin B₁₂, the cure for pernicious anemia was shown crystallographically by Dorothy Crowfoot Hodgkin to consist of a cobalt in a corrin macrocycle. The Watson-Crick structure for DNA demonstrated the key structural role played by phosphate-containing polymers.

Themes in bioinorganic chemistry

Several distinct systems are of identifiable in bioinorganic chemistry. Major areas include:

Metal ion transport and storage

A diverse collection of transporters (e.g. the ion pump NaKATPase), vacuoles, storage proteins (e.g. ferritin), and small molecules (e.g. siderophores) are employed to control metal ions concentration and bio-availability in living organisms. Crucially, many essential metals are not readily accessible to downstream proteins owing to low solubility in aqueous solutions or scarcity in the cellular environment. Organisms have developed a number of strategies for collecting and transporting such elements while limiting their cytotoxicity.

Enzymology

Many reactions in life sciences involve water and metal ions are often at the catalytic centers (active sites) for these enzymes, i.e. these are metalloproteins. Often the reacting water is a ligand (see metal aquo complex). Examples of hydrolase enzymes are carbonic anhydrase, metallophosphatases, and metalloproteinases. Bioinorganic chemists seek to understand and replicate the function of these metalloproteins.

Metal-containing electron transfer proteins are also common. They can be organized into three major classes: iron–sulfur proteins (such as rubredoxins, ferredoxins, and Rieske proteins), blue copper proteins, and cytochromes. These electron transport proteins are complementary to the non-metal electron transporters nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD). The nitrogen cycle make extensive use of metals for the redox interconversions.

4Fe-4S clusters serve as electron-relays in proteins.

Toxicity

Several metal ions are toxic to humans and other animals. The bioinorganic chemistry of lead in the context of its toxicity has been reviewed.

Oxygen transport and activation proteins

Main article: Transition metal dioxygen complex

Aerobic life make extensive use of metals such as iron, copper, and manganese. Heme is utilized by red blood cells in the form of hemoglobin for oxygen transport and is perhaps the most recognized metal system in biology. Other oxygen transport systems include myoglobin, hemocyanin, and hemerythrin. Oxidases and oxygenases are metal systems found throughout nature that take advantage of oxygen to carry out important reactions such as energy generation in cytochrome c oxidase or small molecule oxidation in cytochrome P450 oxidases or methane monooxygenase. Some metalloproteins are designed to protect a biological system from the potentially harmful effects of oxygen and other reactive oxygen-containing molecules such as hydrogen peroxide. These systems include peroxidases, catalases, and superoxide dismutases. A complementary metalloprotein to those that react with oxygen is the oxygen evolving complex present in plants. This system is part of the complex protein machinery that produces oxygen as plants perform photosynthesis.

Myoglobin is a prominent subject in bioinorganic chemistry, with particular attention to the iron-heme complex that is anchored to the protein.

Bioorganometallic chemistry

Bioorganometallic systems feature metal-carbon bonds as structural elements or as intermediates. Bioorganometallic enzymes and proteins include the hydrogenases, FeMoco in nitrogenase, and methylcobalamin. These naturally occurring organometallic compounds. This area is more focused on the utilization of metals by unicellular organisms. Bioorganometallic compounds are significant in environmental chemistry.

Structure of FeMoco, the catalytic center of nitrogenase.

Metals in medicine

Main article: Metals in medicine

A number of drugs contain metals. This theme relies on the study of the design and mechanism of action of metal-containing pharmaceuticals, and compounds that interact with endogenous metal ions in enzyme active sites. The most widely used anti-cancer drug is cisplatin. MRI contrast agent commonly contain gadolinium. Lithium carbonate has been used to treat the manic phase of bipolar disorder. Gold antiarthritic drugs, e.g. auranofin have been commercialized. Carbon monoxide-releasing molecules are metal complexes have been developed to suppress inflammation by releasing small amounts of carbon monoxide. The cardiovascular and neuronal importance of nitric oxide has been examined, including the enzyme nitric oxide synthase. (See also: nitrogen assimilation.) Besides, metallic transition complexes based on triazolopyrimidines have been tested against several parasite strains.

Environmental chemistry

Main article: Environmental chemistry

Environmental chemistry traditionally emphasizes the interaction of heavy metals with organisms. Methylmercury has caused major disaster called Minamata disease. Arsenic poisoning is a widespread problem owing largely to arsenic contamination of groundwater, which affects many millions of people in developing countries. The metabolism of mercury- and arsenic-containing compounds involves cobalamin-based enzymes.

Biomineralization

Main article: Biomineralization

Biomineralization is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. Such tissues are called mineralized tissues. Examples include silicates in algae and diatoms, carbonates in invertebrates, and calcium phosphates and carbonates in vertebrates. Other examples include copper, iron and gold deposits involving bacteria. Biologically-formed minerals often have special uses such as magnetic sensors in magnetotactic bacteria (Fe₃O₄), gravity sensing devices (CaCO₃, CaSO₄, BaSO₄) and iron storage and mobilization (Fe₂O₃•H₂O in the protein ferritin). Because extracellular iron is strongly involved in inducing calcification, its control is essential in developing shells; the protein ferritin plays an important role in controlling the distribution of iron.

Types of inorganic substances in biology

Alkali and alkaline earth metals

Like many antibiotics, monensin-A is an ionophore that tightly bind Na⁺ (shown in yellow).

The abundant inorganic elements act as ionic electrolytes. The most important ions are sodium, potassium, calcium, magnesium, chloride, phosphate, and bicarbonate. The maintenance of precise gradients across cell membranes maintains osmotic pressure and pH. Ions are also critical for nerves and muscles, as action potentials in these tissues are produced by the exchange of electrolytes between the extracellular fluid and the cytosol. Electrolytes enter and leave cells through proteins in the cell membrane called ion channels. For example, muscle contraction depends upon the movement of calcium, sodium and potassium through ion channels in the cell membrane and T-tubules.

Transition metals

The transition metals are usually present as trace elements in organisms, with zinc and iron being most abundant. These metals are used as protein cofactors and signalling molecules. Many are essential for the activity of enzymes such as catalase and oxygen-carrier proteins such as hemoglobin. These cofactors are tightly to a specific protein; although enzyme cofactors can be modified during catalysis, cofactors always return to their original state after catalysis has taken place. The metal micronutrients are taken up into organisms by specific transporters and bound to storage proteins such as ferritin or metallothionein when not being used. Cobalt is essential for the functioning of vitamin B12.

Main group compounds

Many other elements aside from metals are bio-active. Sulfur and phosphorus are required for all life. Phosphorus almost exclusively exists as phosphate and its various esters. Sulfur exists in a variety of oxidation states, ranging from sulfate (SO₄²⁻) down to sulfide (S²⁻). Selenium is a trace element involved in proteins that are antioxidants. Cadmium is important because of its toxicity.

Noble metal

From Wikipedia, the free encyclopedia

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

 

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Periodic table extract showing approximately how often each element tends to recognized as a noble metal:

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 7  most often (Ru, Rh, Pd, Os, Ir, Pt, Au)  1  often (Ag)  2  sometimes (Cu, Hg)  6  in a limited sense (Tc, Re, As, Sb, Bi, Po)

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The thick black line encloses the seven to eight metals most often to often so recognized. Silver is sometimes not recognized as a noble metal on account of its greater reactivity.

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* may be tarnished in moist air or corrode in an acidic solution containing oxygen and an oxidant † attacked by sulfur or hydrogen sulfide
§ self-attacked by radiation-generated ozone

A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, osmium, iridium) are most often so classified. Silver, copper and mercury are less often to sometimes included as noble metals although each of these usually occurs in nature combined with sulfur.

In more specialized fields of study and applications the number of elements counted as noble metals can be smaller or larger. In physics, there are only three noble metals: copper, silver and gold. In dentistry, silver is not always counted as a noble metal since it is subject to corrosion when present in the mouth. In chemistry, the term noble metal is sometimes applied more broadly to any metallic or semimetallic element that does not react with a weak acid and give off hydrogen gas in the process. This broader set includes copper, mercury, technetium, rhenium, arsenic, antimony, bismuth and polonium, as well as gold, the six platinum group metals, and silver.

Meaning and history

While noble metal lists can differ, they tend to cluster around the six platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum) plus gold.

In addition to this term's function as a compound noun, there are circumstances where noble is used as an adjective for the noun metal. A galvanic series is a hierarchy of metals (or other electrically conductive materials, including composites and semimetals) that runs from noble to active, and allows one to predict how materials will interact in the environment used to generate the series. In this sense of the word, graphite is more noble than silver and the relative nobility of many materials is highly dependent upon context, as for aluminium and stainless steel in conditions of varying pH.

The term noble metal can be traced back to at least the late 14th century and has slightly different meanings in different fields of study and application.

Prior to Mendeleev's publication in 1869 of the first (eventually) widely accepted periodic table, Odling published a table in 1864, in which the "noble metals" rhodium, ruthenium, palladium; and platinum, iridium, and osmium were grouped together, and adjacent to silver and gold.

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  Chalcopyrite, which is copper iron sulfide (CuFeS₂), is the most abundant copper ore mineral
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  One half of a ruthenium bar. Size ~ 40 × 15 × 10 mm. Weight ~44 g

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  Rhodium: 1 g powder, 1g pressed cylinder, 1 g pellet.
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  Palladium
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  Acanthite, or silver sulfide (Ag₂S), is the most important silver ore
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  Osmium crystals, 2.2 g
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  Pieces of pure iridium, 1 g, size: 1–3 mm each
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  Crystals of pure platinum
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  Gold nugget from Australia, nearly 9,000 g or 64 oz
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  Cinnabar or mercury sulfide (HgS) is the most common source ore for refining elemental mercury

Properties

Abundance of the chemical elements in the Earth's crust as a function of atomic number. The rarest elements (shown in yellow, including the noble metals) are not the heaviest, but are rather the siderophile (iron-loving) elements in the Goldschmidt classification of elements. These have been depleted by being relocated deeper into the Earth's core. Their abundance in meteoroid materials is relatively higher. Tellurium and selenium have been depleted from the crust due to formation of volatile hydrides.

Geochemical

The noble metals are siderophiles (iron-lovers). They tend to sink into the Earth's core because they dissolve readily in iron either as solid solutions or in the molten state. Most siderophile elements have practically no affinity whatsoever for oxygen: indeed, oxides of gold are thermodynamically unstable with respect to the elements.

Copper, silver, gold, and the six platinum group metals are the only native metals that occur naturally in relatively large amounts.^{[citation needed]}

Corrosion resistance

Copper is dissolved by nitric acid and aqueous potassium cyanide.

Ruthenium can be dissolved in aqua regia, a highly concentrated mixture of hydrochloric acid and nitric acid, only when in the presence of oxygen, while rhodium must be in a fine pulverized form. Palladium and silver are soluble in nitric acid, with the solubility of silver being limited by the formation of silver chloride precipitate.

Rhenium reacts with oxidizing acids, and hydrogen peroxide, and is said to be tarnished by moist air. Osmium and iridium are chemically inert in ambient conditions. Platinum and gold can be dissolved in aqua regia. Mercury reacts with oxidising acids.

In 2010, US researchers discovered that an organic "aqua regia" in the form of a mixture of thionyl chloride SOCl₂ and the organic solvent pyridine C₅H₅N achieved "high dissolution rates of noble metals under mild conditions, with the added benefit of being tunable to a specific metal" for example, gold but not palladium or platinum.

Electronic

In physics, the expression "noble metal" is sometimes confined to copper, silver, and gold, since their full d-subshells contribute to what noble character they have. In contrast, the other noble metals, especially the platinum group metals, have notable catalytic applications, arising from their partially filled d-subshells. This is the case with palladium which has a full d-subshell in the atomic state but in condensed form has a partially filled sp band at the expense of d-band occupancy.

The difference in reactivity can be seen during the preparation of clean metal surfaces in an ultra-high vacuum: surfaces of "physically defined" noble metals (e.g., gold) are easy to clean and keep clean for a long time, while those of platinum or palladium, for example, are covered by carbon monoxide very quickly.

Electrochemical

Standard reduction potentials in aqueous solution are also a useful way of predicting the non-aqueous chemistry of the metals involved. Thus, metals with high negative potentials, such as sodium, or potassium, will ignite in air, forming the respective oxides. These fires cannot be extinguished with water, which also react with the metals involved to give hydrogen, which is itself explosive. Noble metals, in contrast, are disinclined to react with oxygen and, for that reason (as well as their scarcity) have been valued for millennia, and used in jewellery and coins.

Electrochemical properties of some metals and metalloids

Element	Z	G	P	Reaction	SRP(V)	EN	EA
Gold ✣	79	11	6	Au3+ + 3 e− → Au	1.5	2.54	223
Platinum ✣	78	10	6	Pt2+ + 2 e− → Pt	1.2	2.28	205
Iridium ✣	77	9	6	Ir3+ + 3 e− → Ir	1.16	2.2	151
Palladium ✣	46	10	5	Pd2+ + 2 e− → Pd	0.915	2.2	54
Osmium ✣	76	8	6	OsO 2 + 4 H+ + 4 e− → Os + 2 H 2O	0.85	2.2	104
Mercury	80	12	6	Hg2+ + 2 e− → Hg	0.85	2.0	−50
Rhodium ✣	45	9	5	Rh3+ + 3 e− → Rh	0.8	2.28	110
Silver ✣	47	11	5	Ag+ + e− → Ag	0.7993	1.93	126
Ruthenium ✣	44	8	5	Ru3+ + 3 e− → Ru	0.6	2.2	101
Polonium ☢	84	16	6	Po2+ + 2 e− → Po	0.6	2.0	136
Water				2 H 2O + 4 e− +O 2 → 4 OH−	0.4
Copper	29	11	4	Cu2+ + 2 e− → Cu	0.339	2.0	119
Bismuth	83	15	6	Bi3+ + 3 e− → Bi	0.308	2.02	91
Technetium ☢	43	7	6	TcO 2 + 4 H+ + 4 e− → Tc + 2 H 2O	0.28	1.9	53
Rhenium	75	7	6	ReO 2 + 4 H+ + 4 e− → Re + 2 H 2O	0.251	1.9	6
ArsenicMD	33	15	4	As 4O 6 + 12 H+ + 12 e− → 4 As + 6 H 2O	0.24	2.18	78
AntimonyMD	51	15	5	Sb 2O 3 + 6 H+ + 6 e− → 2 Sb + 3 H 2O	0.147	2.05	101
Z atomic number; G group; P period; SRP standard reduction potential; EN electronegativity; EA electron affinity
✣ traditionally recognized as a noble metal; MD metalloid; ☢ radioactive

The adjacent table lists standard reduction potential in volts; electronegativity (revised Pauling); and electron affinity values (kJ/mol), for some metals and metalloids.

The simplified entries in the reaction column can be read in detail from the Pourbaix diagrams of the considered element in water. Noble metals have large positive potentials; elements not in this table have a negative standard potential or are not metals.

Electronegativity is included since it is reckoned to be, "a major driver of metal nobleness and reactivity".

On account of their high electron affinity values, the incorporation of a noble metal in the electrochemical photolysis process, such as platinum and gold, among others, can increase photoactivity.

Arsenic and antimony are usually considered to be metalloids rather than noble metals. However, physically speaking their most stable allotropes are metallic. Semiconductors, such as selenium and tellurium, have been excluded.

The black tarnish commonly seen on silver arises from its sensitivity to hydrogen sulfide: 2Ag + H₂S + 1/2O₂ → Ag₂S + H₂O. Rayner-Canham contends that, "silver is so much more chemically-reactive and has such a different chemistry, that it should not be considered as a 'noble metal'." In dentistry, silver is not regarded as a noble metal due to its tendency to corrode in the oral environment.

The relevance of the entry for water is addressed by Li et al. in the context of galvanic corrosion. Such a process will only occur when:

"(1) two metals which have different electrochemical potentials are...connected, (2) an aqueous phase with electrolyte exists, and (3) one of the two metals has...potential lower than the potential of the reaction (H
₂O + 4e +O
₂ = 4 OH^•) which is 0.4 V...The...metal with...a potential less than 0.4 V acts as an anode...loses electrons...and dissolves in the aqueous medium. The noble metal (with higher electrochemical potential) acts as a cathode and, under many conditions, the reaction on this electrode is generally H
₂O − 4 e^• − O
₂ = 4 OH^•)."

The superheavy elements from hassium (element 108) to livermorium (116) inclusive are expected to be "partially very noble metals"; chemical investigations of hassium has established that it behaves like its lighter congener osmium, and preliminary investigations of nihonium and flerovium have suggested but not definitively established noble behavior. Copernicium's behaviour seems to partly resemble both its lighter congener mercury and the noble gas radon.

Oxides

Oxide melting points, °C

Element	I	II	III	IV	VI	VII
Copper		1326
Ruthenium				d1300 d75+
Rhodium			d1100 ?
Palladium		d750
Silver	d200
Rhenium						327
Osmium				d500
Iridium				d1100 ?
Platinum				450 d100
Gold			d150
Mercury		d500
Strontium‡		2430
Molybdenum‡					801 d70
AntimonyMD			655
Lanthanum‡			2320
Bismuth‡			817
d = decomposes; if there are two figures, the 2nd is for the hydrated form; ‡ = not a noble metal; MD = metalloid

As long ago as 1890, Hiorns observed as follows:

"Noble Metals. Gold, Platinum, Silver, and a few rare metals. The members of this class have little or no tendency to unite with oxygen in the free state, and when placed in water at a red heat do not alter its composition. The oxides are readily decomposed by heat in consequence of the feeble affinity between the metal and oxygen."

Smith, writing in 1946, continued the theme:

"There is no sharp dividing line [between 'noble metals' and 'base metals'] but perhaps the best definition of a noble metal is a metal whose oxide is easily decomposed at a temperature below a red heat."

"It follows from this that noble metals...have little attraction for oxygen and are consequently not oxidised or discoloured at moderate temperatures."

Such nobility is mainly associated with the relatively high electronegativity values of the noble metals, resulting in only weakly polar covalent bonding with oxygen. The table lists the melting points of the oxides of the noble metals, and for some of those of the non-noble metals, for the elements in their most stable oxidation states.

Catalytic properties

Many of the noble metals can act as catalysts. For example, platinum is used in catalytic converters, devices which convert toxic gases produced in car engines, such as the oxides of nitrogen, into non-polluting substances.

Gold has many industrial applications; it is used as a catalyst in hydrogenation and the water gas shift reaction.