List of chemical elements

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A chemical element is any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Elements are the fundamental materials of which all matter is composed. Here, the elements are ordered alphabetically. Each element is followed by its atomic number, the total number of protons in the atomic nucleus. (See also periodic table of the elements.)

Chemical compound

Print Cite Share MoreWRITTEN BYRichard O.C. NormanSee All ContributorsRector, Exeter College, University of Oxford. Professor of Chemistry, University of York, England, 1956–87. Author of Principles of Organic Synthesis.See Article History

Chemical compound, any substance composed of identical molecules consisting of atoms of two or more chemical elements.

Reaction types

The electronic features of functional groups are responsible for the types of reactions that are characteristic of each group (see above Functional groups). Because there is a great deal of similarity in the electronic characteristics of the different functional groups, there is a corresponding similarity in the types of reaction that different groups undergo. Just as the properties of the multitude of organic compounds are made more comprehensible by considering the reactions of a specific functional group, so too can the plethora of organic reactions be made more understandable by categorization into common types of chemical reaction, such as substitution, elimination, addition, hydrolysis, condensation, and acid-base and oxidation-reduction reactions.

Organic compounds

In general, organic compounds are substances that contain carbon (C), and carbon atoms provide the key structural framework that generates the vast diversity of organic compounds. All things on the Earth (and most likely elsewhere in the universe) that can be described as living have a crucial dependence on organic compounds. Foodstuffs—namely, fats, proteins, and carbohydrates—are organic compounds, as are such vital substances as hemoglobin, chlorophyll, enzymes, hormones, and vitamins.

Inorganic compounds

Inorganic compounds include compounds that are made up of two or more elements other than carbon, as well as certain carbon-containing compounds that lack carbon-carbon bonds, such as cyanides and carbonates. Inorganic compounds are most often classified in terms of the elements or groups of elements that they contain. Oxides, for example, can be either ionic or molecular. Ionic oxides contain O²⁻ (oxide) ions and metal cations, whereas molecular oxides contain molecules in which oxygen (O) is covalently bonded to other nonmetals such as sulfur (S) or nitrogen (N).

Lawrencium – Lr

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Titles: Lr, element 103

Lawrencium (Lr), synthetic chemical element, the 14th member of the actinoid series of the periodic table, atomic number 103. Not occurring in nature, lawrencium (probably as the isotope lawrencium-257) was first produced (1961) by chemists Albert Ghiorso, T. Sikkeland, A.E. Larsh, and R.M. Latimer at the University of California, Berkeley, by bombarding a mixture of the longest-lived isotopes of californium (atomic number 98) with boron ions (atomic number 5) accelerated in a heavy-ion linear accelerator. The element was named after American physicist Ernest O. Lawrence.

Nobelium – No

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Titles: No, element 102

Nobelium (No), synthetic chemical element of the actinoid series of the periodic table, atomic number 102. The element was named after Swedish chemist Alfred Nobel.

Mendelevium – Md

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Titles: Md, element 101

Mendelevium (Md), synthetic chemical element of the actinoid series of the periodic table, atomic number 101. It was the first element to be synthesized and discovered a few atoms at a time. Not occurring in nature, mendelevium (as the isotope mendelevium-256) was discovered (1955) by American chemists Albert Ghiorso, Bernard G. Harvey, Gregory R. Choppin, Stanley G. Thompson, and Glenn T. Seaborg at the University of California, Berkeley, as a product resulting from the helium–ion (alpha-particle) bombardment of a minute quantity (about a billion atoms) of einsteinium-253 (atomic number 99). The element was named after Russian chemist Dmitry Mendeleyev.

Fermium – Fm

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Titles: Fm, element 100

Fermium (Fm), synthetic chemical element of the actinoid series of the periodic table, atomic number 100. Fermium (as the isotope fermium-255) is produced by the intense neutron irradiation of uranium-238 and was first positively identified by American chemist Albert Ghiorso and coworkers at Berkeley, California, in debris taken from the first thermonuclear (hydrogen bomb) test explosion (November 1952), “Mike,” in the South Pacific. The element was named after the Italian-born American physicist Enrico Fermi.

Einsteinium – Es

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Title: Es

Einsteinium (Es), synthetic chemical element of the actinoid series of the periodic table, atomic number 99. Not occurring in nature, einsteinium (as the isotope einsteinium-253) was first produced by intense neutron irradiation of uranium-238 during the detonation of nuclear weapons. This isotope was identified in December 1952 by Albert Ghiorso and coworkers at Berkeley, California, in debris taken from the first thermonuclear (hydrogen bomb) explosion, “Mike,” in the South Pacific (November 1952). The element was named after the German-born physicist Albert Einstein.