A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.

As of November 2011, 118 elements have been identified, the latest being ununoctium in 2002. Of the 118 known elements, only the first 94 are known to occur naturally on Earth (88 in non-trace amounts). Of these, 80 are stable or essentially so, while the others are radioactive, decaying into lighter elements over various timescales from fractions of a second to billions of years. Additional elements, of higher atomic numbers than those naturally occurring, have been produced artificially as the synthetic products of man-made nuclear reactions.

Hydrogen and helium are by far the most abundant elements in the universe. However, iron is the most abundant element (by mass) making up the Earth, and oxygen is the most common element in the Earth's crust. Although all known chemical matter is composed of these elements, chemical matter itself constitutes only about 15% of the matter in the universe. The remainder is dark matter, a mysterious substance which is not composed of chemical elements since it lacks protons, neutrons or electrons.

The chemical elements are thought to have been produced by various cosmic processes, including hydrogen, helium (and smaller amounts of lithium, beryllium and boron) created during the Big Bang and cosmic-ray spallation. Production of heavier elements, from carbon to the very heaviest elements, proceeds by stellar nucleosynthesis, and these were made available for later solar system and planetary formation by supernovae, which blast these elements into space. The high abundance of oxygen, silicon, and iron on Earth reflect their common production in such stars, after the lighter gaseous elements and their compounds have been subtracted. While most elements are generally viewed as stable, a small amount of natural transformation of one element to another also occurs in the present time, through decay of radioactive elements as well as other natural nuclear processes.

Relatively pure samples of isolated elements are uncommon in nature. While all of the 94 naturally occurring elements have been identified in mineral samples from the Earth's crust, only a small minority of elements are found as recognizable, relative pure minerals. Among the more common of such "native elements" are copper, silver, gold, carbon (as coal, graphite, or diamonds), sulfur, and mercury. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined form, most of these occur as mixtures. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, and native solid elements occur in alloys, such as that of iron and nickel.

When two distinct elements are chemically combined, with the atoms held together by chemical bonds, the result is termed a chemical compound. Two thirds of the chemical elements occur on Earth only as compounds, and in the remaining third, often the compound forms of the element are most common. Chemical compounds may be composed of elements combined in exact whole-number ratios of atoms, as in water, table salt, and minerals as quartz, calcite, and some ores. However, chemical bonding of many types of elements results in crystalline solids and metallic alloys for which exact chemical formulas do not exist. Most of the solid substance of the Earth is of this latter type. The substances that form Earth's crust, mantle, and core do not have precise chemical empirical formulas.

The history of discovery and use of the elements began with primitive human societies that found native elements like copper and gold, and extracted (smelted) iron and a few other metals from their ores. Alchemists and chemists subsequently identified many more, with nearly all of the naturally-occurring elements known by 1900. The properties of the chemical elements are often summarized using the periodic table that organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. Either in its pure forms, or in various chemical compounds or mixtures, almost every element has at least one important human use. Save for short half-lived radioactive elements, all of the elements are available industrially, most to high degrees of purity.

Around two dozen of the elements are essential to various kinds of biological life. Most rare elements on Earth are not needed by life (exceptions being selenium and iodine), while a few quite common ones (aluminum and titanium) are not used. Most organisms share element needs, with a few differences. For example, ocean algae use bromine but land plants and animals seem to need none, and all animals require sodium, but some plants do not. Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus—make up almost 99% of the mass of a human body. In addition to the six major elements that compose most of the human body, humans require consumption of at least a dozen more elements in the form of certain chemical compounds.

List of the 118 known chemical elementsEdit

The following sortable table includes the 118 known chemical elements, with the names linking to the Wikipedia articles on each.

• Atomic number, name, and symbol all serve independently as unique identifiers.
• Names are those accepted by IUPAC; provisional names for recently produced elements not yet formally named are in parentheses.
• Group, period, and block refer to an element's position in the periodic table.
• State of matter (solid, liquid, or gas) applies at standard temperature and pressure conditions (STP).^{[citation needed]}
• Occurrence distinguishes naturally occurring elements, categorized as either primordial or transient (from decay), and additional synthetic elements that have been produced technologically, but are not known to occur naturally.
• Description summarizes an element's properties using the broad categories commonly presented in periodic tables: Actinide, alkali metal, alkaline earth metal, halogen, lanthanide, metal, metalloid, noble gas, non-metal, and transition metal.

List of elements

Atomic no.	Name	Symbol	Group	Period	Block	State at STP	Occurrence	Description
1	Hydrogen	H	1	1	s	Gas	Primordial	Non-metal
2	Helium	He	18	1	s	Gas	Primordial	Noble gas
3	Lithium	Li	1	2	s	Solid	Primordial	Alkali metal
4	Beryllium	Be	2	2	s	Solid	Primordial	Alkaline earth metal
5	Boron	B	13	2	p	Solid	Primordial	Metalloid
6	Carbon	C	14	2	p	Solid	Primordial	Non-metal
7	Nitrogen	N	15	2	p	Gas	Primordial	Non-metal
8	Oxygen	O	16	2	p	Gas	Primordial	Non-metal
9	Fluorine	F	17	2	p	Gas	Primordial	Halogen
10	Neon	Ne	18	2	p	Gas	Primordial	Noble gas
11	Sodium	Na	1	3	s	Solid	Primordial	Alkali metal
12	Magnesium	Mg	2	3	s	Solid	Primordial	Alkaline earth metal
13	Aluminium	Al	13	3	p	Solid	Primordial	Metal
14	Silicon	Si	14	3	p	Solid	Primordial	Metalloid
15	Phosphorus	P	15	3	p	Solid	Primordial	Non-metal
16	Sulfur	S	16	3	p	Solid	Primordial	Non-metal
17	Chlorine	Cl	17	3	p	Gas	Primordial	Halogen
18	Argon	Ar	18	3	p	Gas	Primordial	Noble gas
19	Potassium	K	1	4	s	Solid	Primordial	Alkali metal
20	Calcium	Ca	2	4	s	Solid	Primordial	Alkaline earth metal
21	Scandium	Sc	3	4	d	Solid	Primordial	Transition metal
22	Titanium	Ti	4	4	d	Solid	Primordial	Transition metal
23	Vanadium	V	5	4	d	Solid	Primordial	Transition metal
24	Chromium	Cr	6	4	d	Solid	Primordial	Transition metal
25	Manganese	Mn	7	4	d	Solid	Primordial	Transition metal
26	Iron	Fe	8	4	d	Solid	Primordial	Transition metal
27	Cobalt	Co	9	4	d	Solid	Primordial	Transition metal
28	Nickel	Ni	10	4	d	Solid	Primordial	Transition metal
29	Copper	Cu	11	4	d	Solid	Primordial	Transition metal
30	Zinc	Zn	12	4	d	Solid	Primordial	Transition metal
31	Gallium	Ga	13	4	p	Solid	Primordial	Metal
32	Germanium	Ge	14	4	p	Solid	Primordial	Metalloid
33	Arsenic	As	15	4	p	Solid	Primordial	Metalloid
34	Selenium	Se	16	4	p	Solid	Primordial	Non-metal
35	Bromine	Br	17	4	p	Liquid	Primordial	Halogen
36	Krypton	Kr	18	4	p	Gas	Primordial	Noble gas
37	Rubidium	Rb	1	5	s	Solid	Primordial	Alkali metal
38	Strontium	Sr	2	5	s	Solid	Primordial	Alkaline earth metal
39	Yttrium	Y	3	5	d	Solid	Primordial	Transition metal
40	Zirconium	Zr	4	5	d	Solid	Primordial	Transition metal
41	Niobium	Nb	5	5	d	Solid	Primordial	Transition metal
42	Molybdenum	Mo	6	5	d	Solid	Primordial	Transition metal
43	Technetium	Tc	7	5	d	Solid	Transient	Transition metal
44	Ruthenium	Ru	8	5	d	Solid	Primordial	Transition metal
45	Rhodium	Rh	9	5	d	Solid	Primordial	Transition metal
46	Palladium	Pd	10	5	d	Solid	Primordial	Transition metal
47	Silver	Ag	11	5	d	Solid	Primordial	Transition metal
48	Cadmium	Cd	12	5	d	Solid	Primordial	Transition metal
49	Indium	In	13	5	p	Solid	Primordial	Metal
50	Tin	Sn	14	5	p	Solid	Primordial	Metal
51	Antimony	Sb	15	5	p	Solid	Primordial	Metalloid
52	Tellurium	Te	16	5	p	Solid	Primordial	Metalloid
53	Iodine	I	17	5	p	Solid	Primordial	Halogen
54	Xenon	Xe	18	5	p	Gas	Primordial	Noble gas
55	Caesium	Cs	1	6	s	Solid	Primordial	Alkali metal
56	Barium	Ba	2	6	s	Solid	Primordial	Alkaline earth metal
57	Lanthanum	La	3	6	f	Solid	Primordial	Lanthanide
58	Cerium	Ce	3	6	f	Solid	Primordial	Lanthanide
59	Praseodymium	Pr	3	6	f	Solid	Primordial	Lanthanide
60	Neodymium	Nd	3	6	f	Solid	Primordial	Lanthanide
61	Promethium	Pm	3	6	f	Solid	Transient	Lanthanide
62	Samarium	Sm	3	6	f	Solid	Primordial	Lanthanide
63	Europium	Eu	3	6	f	Solid	Primordial	Lanthanide
64	Gadolinium	Gd	3	6	f	Solid	Primordial	Lanthanide
65	Terbium	Tb	3	6	f	Solid	Primordial	Lanthanide
66	Dysprosium	Dy	3	6	f	Solid	Primordial	Lanthanide
67	Holmium	Ho	3	6	f	Solid	Primordial	Lanthanide
68	Erbium	Er	3	6	f	Solid	Primordial	Lanthanide
69	Thulium	Tm	3	6	f	Solid	Primordial	Lanthanide
70	Ytterbium	Yb	3	6	f	Solid	Primordial	Lanthanide
71	Lutetium	Lu	3	6	d	Solid	Primordial	Lanthanide
72	Hafnium	Hf	4	6	d	Solid	Primordial	Transition metal
73	Tantalum	Ta	5	6	d	Solid	Primordial	Transition metal
74	Tungsten	W	6	6	d	Solid	Primordial	Transition metal
75	Rhenium	Re	7	6	d	Solid	Primordial	Transition metal
76	Osmium	Os	8	6	d	Solid	Primordial	Transition metal
77	Iridium	Ir	9	6	d	Solid	Primordial	Transition metal
78	Platinum	Pt	10	6	d	Solid	Primordial	Transition metal
79	Gold	Au	11	6	d	Solid	Primordial	Transition metal
80	Mercury	Hg	12	6	d	Liquid	Primordial	Transition metal
81	Thallium	Tl	13	6	p	Solid	Primordial	Metal
82	Lead	Pb	14	6	p	Solid	Primordial	Metal
83	Bismuth	Bi	15	6	p	Solid	Primordial	Metal
84	Polonium	Po	16	6	p	Solid	Transient	Metalloid
85	Astatine	At	17	6	p	Solid	Transient	Halogen
86	Radon	Rn	18	6	p	Gas	Transient	Noble gas
87	Francium	Fr	1	7	s	Solid	Transient	Alkali metal
88	Radium	Ra	2	7	s	Solid	Transient	Alkaline earth metal
89	Actinium	Ac	3	7	f	Solid	Transient	Actinide
90	Thorium	Th	3	7	f	Solid	Primordial	Actinide
91	Protactinium	Pa	3	7	f	Solid	Transient	Actinide
92	Uranium	U	3	7	f	Solid	Primordial	Actinide
93	Neptunium	Np	3	7	f	Solid	Transient	Actinide
94	Plutonium	Pu	3	7	f	Solid	Primordial	Actinide
95	Americium	Am	3	7	f	Solid	Synthetic	Actinide
96	Curium	Cm	3	7	f	Solid	Synthetic	Actinide
97	Berkelium	Bk	3	7	f	Solid	Synthetic	Actinide
98	Californium	Cf	3	7	f	Solid	Synthetic	Actinide
99	Einsteinium	Es	3	7	f	Solid	Synthetic	Actinide
100	Fermium	Fm	3	7	f	Solid	Synthetic	Actinide
101	Mendelevium	Md	3	7	f	Solid	Synthetic	Actinide
102	Nobelium	No	3	7	f	Solid	Synthetic	Actinide
103	Lawrencium	Lr	3	7	d	Solid	Synthetic	Actinide
104	Rutherfordium	Rf	4	7	d		Synthetic	Transition metal
105	Dubnium	Db	5	7	d		Synthetic	Transition metal
106	Seaborgium	Sg	6	7	d		Synthetic	Transition metal
107	Bohrium	Bh	7	7	d		Synthetic	Transition metal
108	Hassium	Hs	8	7	d		Synthetic	Transition metal
109	Meitnerium	Mt	9	7	d		Synthetic
110	Darmstadtium	Ds	10	7	d		Synthetic
111	Roentgenium	Rg	11	7	d		Synthetic
112	Copernicium	Cn	12	7	d		Synthetic	Transition metal
113	(Ununtrium)	Uut	13	7	p		Synthetic
114	Flerovium	Fl	14	7	p		Synthetic
115	(Ununpentium)	Uup	15	7	p		Synthetic
116	Livermorium	Lv	16	7	p		Synthetic
117	(Ununseptium)	Uus	17	7	p		Synthetic
118	(Ununoctium)	Uuo	18	7	p		Synthetic