Chemical elements

In science and frequently chemistry, chemical elements are a pure chemical substances consisting of a single type of atom distinguished by its atomic number, which is the number of protons in its atomic nucleus.  This also means that elements can’t be broken down further by ordinary chemical reactions


Pure gold crystals about 14mm across. image: adapted from wikipedia

Elements are divided into metals, metalloids, and non-metals. Familiar examples of elements are:


The lightest chemical elements, including hydrogen, helium and smaller amounts of lithium, beryllium and boron, are thought to have been produced by various cosmic processes during the Big Bang and cosmic-ray spallation. 

Production of heavier elements, from carbon to the very heaviest elements, proceeded by stellar nucleosynthesis, and these were made available for later solar system and planetary formation by planetary nebulae and supernovae, which blast these elements into space.

The high abundance of oxygen, silicon, and iron on Earth reflects their common production in such stars. While most elements are generally stable, a small amount of natural transformation of one element to another also occurs in the decay of radioactive elements as well as other natural nuclear processes.

Early history and eventual organisation of the elements

The history of the 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 becoming known by 1900. The properties of the chemical elements are often summarized using the periodic table, which organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. Save for unstable radioactive elements with short half lives, all of the elements are available industrially, most of them in high degrees of purity.

Abundance of the elements

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 Earth's crust.  Although all known chemical matter is composed of these elements, chemical matter itself is hypothesized to constitute only about 15% of the matter in the universe. The remainder is believed to be dark matter, a range of substances whose composition is largely unknown and not composed of chemical elements, since it lacks protons, neutrons or electrons. Dark matter may also include normal baryonic matter and neutrinos.


Chemistry of the elements

When two or more 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 naturally 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 such 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.

 Relatively pure samples of isolated elements are uncommon in nature. While all of the 98 naturally occurring elements have been identified in mineral samples from Earth's crust, only a small minority of elements are found as recognizable, relatively 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.

As of November 2011, 118 elements have been identified, the latest being ununseptium in 2010. Of the 118 known elements, only the first 98 are known to occur naturally on Earth; 80 of them are stable, while the others are radioactive, decaying into lighter elements over various timescales from fractions of a second to billions of years. 

Those elements that do not occur naturally on Earth have been produced artificially as the synthetic products nuclear reactions.

sourcehttp://en.wikipedia.org/w/index.php?title=Chemical_element&oldid=603493951


This simplified diagram represents the element and atomic isotope helium 3He. The proton and neutron size are not to scale to the cloud of possible places electrons around the nucleus.

Unstable elements

Some elements though have so many protons and neutrons that the forces holding them together are not strong enough and so the element falls apart and starts to transform into another element. These unstable elements are also radioactive. 

Elements are divided into metals, metalloids, and non-metals. Mainly because most elements have metallic properties. Chemists also organise the elements into a table commonly refered to as The Periodic Table of the Elements.

Although some elements can be considered natural. Many elements don't exist in their pure form in nature due to their chemical or atomic instability. 

Here is a list of known elements briefly explained:

Hydrogen

800px-Hydrogen_discharge_tube.jpg

Atomic number: 1

Symbol: H

Category: non-metal

Density at 25°C: gas 

Hydrogen …

Helium

800px-Helium_discharge_tube.jpg

Atomic number: 2

Symbol: He

Category: non-metal, noble gas

Density at 25°C

Lithium

250px-Lithium_paraffin.jpg

Atomic number: 3

Symbol: Li

Category: metal

Density at 25°C: solid, 0.534 g·…

Beryllium

150px-Be-140g.jpg

Atomic number: 4

Symbol: Be

Category: metal

Density at 25°C: solid, 1.85 g·cm−…

Boron

125px-Bor_1.jpg

Atomic number: 5

Symbol: B

Category: metalloid

Density at 25°C: solid, varies …

Carbon

Diamond-and-graphite-with-scale.jpg

Atomic number: 6

Symbol: C

Category: non metal

Density at 25°C: solid, varies …

Nitrogen

800px-Nitrogen_discharge_tube.jpg

Atomic number: 7

Symbol: N

Category: non metal

Density at 25°C: gas

Adding an …

Oxygen

800px-Oxygen_discharge_tube.jpg

Atomic number: 8

Symbol: O

Category: non metal

Density at 25°C: gas

Another …

Fluorine

Liquid_fluorine_tighter_crop.jpg

Atomic number: 9

Symbol: F

Category: Non-metal - Halogen

Density at 25°C: gas, …

Neon

220px-NeTube.jpg

Atomic number: 10

Symbol: Ne

Category: non metal

Density at 25°C: gas, but 1.3 …

Sodium

250px-Nametal.JPG.jpg

Atomic number: 11

Symbol: Na

Category: metal

Density at 25°C: solid,  0.968 …

Magnesium

Atomic number: 12

Symbol: Mg

Category: metal

Density at 25°C: solid,  1.738 …

Aluminium

Atomic number: 13

Symbol: Al

Category: metal

Density at 25°C: solid,  2.70 g·…

Silicon

Atomic number: 14

Symbol: Si

Category: metalloid

Density at 25°C: solid,  2.70 …

Phosphorus

Atomic number: 15

Symbol: P

Category: non-metal

Density at 25°C: solid, varies …

Sulphur

Atomic number: 16

Symbol: S

Category: non-metal

Density at 25°C: solid, varies …

Chlorine

Atomic number: 17

Symbol: Cl

Category: non-metal

Density at 25°C: gas

Chlorine …

Argon

800px-Argon_discharge_tube.jpg

Atomic number: 18

Symbol: Ar

Category: non-metal

Density at 25°C: gas

Argon …

Potassium

Atomic number: 19

Symbol: K

Category: metal

Density at 25°C: solid

Potassium …

Calcium

250px-Calcium_unter_Argon_Schutzgasatmosphäre.jpg

Atomic number: 20

Symbol: Ca

Category: metal

Density at 25°C: solid

Another …

Scandium

Atomic number: 21

Symbol: Sc

Category: transition metal

Density at 25°C: solid …

Titanium

Atomic number: 22

Symbol: Ti

Category: transition metal

Density at 25°C: solid …

Vanadium

Atomic number: 23

Symbol: V

Category: transition metal

Density at 25°C: solid  

Chromium

Atomic number: 24

Symbol: Cr

Category: transition metal

Density at 25°C: solid  

Manganese

Atomic number: 25

Symbol: Mn

Category: transition metal

Density at 25°C: solid  

Iron

Atomic number: 26

Symbol: Fe

Category: transition metal

Density at 25°C: solid  

Cobalt

Atomic number: 27

Symbol: Co

Category: transition metal

Density at 25°C: solid 

Nickel

Atomic number: 28

Symbol: Ni

Category: transition metal

Density at 25°C: solid:  

Copper

Atomic number: 29

Symbol: Cu

Category: transition metal

Density at 25°C: solid:  

Zinc

Atomic number: 30

Symbol: Zn

Category: transition metal

Density at 25°C: solid:  

Gallium

Atomic number: 31

Symbol: Ga

Category: post-transition metal

Density at 25°C: …

Germanium

Atomic number: 32

Symbol: Ge

Category: metalloid

Density at 25°C: solid:  5.323 …

Arsenic

Arsen_1a.jpg

Atomic number: 33

Symbol: As

Category: metalloid

Density at 25°C: solid:  5.727 …

Selenium

Atomic number: 34

Symbol: Se

Category: metalloid sometimes non-metal

Density …

Bromine

Atomic number: 35

Symbol: Br

Category: halogen

Density at 25°C: liquid/gas:

Krypton

800px-KrTube.jpg

Atomic number: 36

Symbol: Kr

Category: noble gas

Density at 25°C: gas

This is …

Rubidium

Atomic number: 37

Symbol: Rb

Category: alkali metal

Density at 25°C: solid:  …

Strontium

Atomic number: 38

Symbol: Sr

Category: alkali earth metal

Density at 25°C: solid:  …

Yttrium

Atomic number: 39

Symbol: Y

Category: transition metal

Density at 25°C: solid:  …

Zirconium

Atomic number: 40

Symbol: Zr

Category: transition metal

Density at 25°C: solid:  …

Niobium

Atomic number: 41

Symbol: Nb

Category: transition metal

Density at 25°C: solid:  …

Molybdenum

Atomic number: 42

Symbol: Mo

Category: transition metal

Density at 25°C: solid:  …

Technetium

Atomic number: 43

Symbol: Tc

Category: transition metal

Density at 25°C: solid:  …

Ruthenium

Atomic number: 44

Symbol: Ru

Category: transition metal

Density at 25°C: solid:  …

Rhodium

Atomic number: 45

Symbol: Rh

Category: transition metal

Density at 25°C: solid:  …

Palladium

Atomic number: 46

Symbol: Pd

Category: transition metal

Density at 25°C: solid:  …

Silver

silver.jpg

Atomic number: 47

Symbol: Ag

Category: transition metal

Density at 25°C: solid:  …

Cadmium

Atomic number: 48

Symbol: Cd

Category: transition metal

Density at 25°C: solid:  …

Indium

Atomic number: 49

Symbol: In

Category: post transition metal

Density at 25°C: …

Tin

Atomic number: 50

Symbol: Sn

Category: post transition metal

Density at 25°C: …

Antimony

Atomic number: 51

Symbol: Sb

Category: metalloid

Density at 25°C: solid:  6.697 …

Tellurium

Atomic number: 52

Symbol: Te

Category: metalloid

Density at 25°C: solid:  6.24 …

Iodine

Atomic number: 53

Symbol: I

Category: halogen

Density at 25°C: solid:  4.933 …

Xenon

Atomic number: 54

Symbol: Xe

Category: noble gas

Density at 25°C: gas

This is …

Caesium

Atomic number: 55

Symbol: Cs

Category: alkali metal

Density at 25°C: solid: …

Barium

Atomic number: 56
Symbol: Ba
Category: alkali earth metal

Density at 25°C: solid: …

Lanthanum

Atomic number: 57

Symbol: La

Category: lanthanoid metal

Density at 25°C: solid: …

Cerium

Atomic number: 58

Symbol: Ce

Category: lanthanoid metal

Density at 25°C: solid: …

Praseodymium

Atomic number: 59

Symbol: Pr

Category: lanthanoid metal

Density at 25°C: solid: …

Neodymium

Atomic number: 60

Symbol: Nd

Category: lanthanoid metal

Density at 25°C: solid: …

Promethium

Atomic number: 61

Symbol: Pm

Category: lanthanoid metal

Density at 25°C: solid: …

Samarium

Atomic number: 62

Symbol: Sm

Category: lanthanoid metal

Density at 25°C: solid: …

Europium

Atomic number: 63

Symbol: Eu

Category: lanthanoid metal

Density at 25°C: solid: …

Gadolinium

Atomic number: 64

Symbol: Gd

Category: lanthanoid metal

Density at 25°C: solid: …

Terbium

Atomic number: 65

Symbol: Tb

Category: lanthanoid metal

Density at 25°C: solid: …

Dysprosium

Atomic number: 66

Symbol: Dy

Category: lanthanoid metal

Density at 25°C: solid: …

Holmium

Atomic number: 67

Symbol: Ho

Category: lanthanoid metal

Density at 25°C: solid: …

Erbium

Atomic number: 68

Symbol: Er

Category: lanthanoid metal

Density at 25°C: solid: …

Thulium

Atomic number: 69

Symbol: Tm

Category: lanthanoid metal

Density at 25°C: solid: …

Ytterbium

Atomic number: 70

Symbol: Yb

Category: lanthanoid metal

Density at 25°C: solid: …

Lutetium

Atomic number: 71

Symbol: Lu

Category: lanthanoid metal

Density at 25°C: solid: …

Hafnium

Atomic number: 72

Symbol: Hf

Category: transition metal

Density at 25°C: solid: …

Tantalum

Atomic number: 73

Symbol: Ta

Category: transition metal

Density at 25°C: solid: …

Tungsten

Atomic number: 74

Symbol: W

Category: transition metal

Density at 25°C: solid: …

Rhenium

Atomic number: 75

Symbol: Re

Category: transition metal

Density at 25°C: solid: …

Osmium

Atomic number: 76

Symbol: Os

Category: transition metal

Density at 25°C: solid: …

Iridium

Atomic number: 77

Symbol: Ir

Category: transition metal

Density at 25°C: solid: …

Platinum

Atomic number: 78

Symbol: Pt

Category: transition metal (noble metal)

Density …

Gold

Atomic number: 79

Symbol: Au

Category: transition metal 

Density at 25°C: solid: …

Mercury

Atomic number: 80

Symbol: Hg

Category: transition metal 

Density at 25°C: solid: …

Thallium

Atomic number: 81

Symbol: Tl

Category: transition metal 

Density at 25°C: solid: …

Lead

Atomic number: 82

Symbol: Pb

Category: post-transition metal (poor conductor …

Bismuth

Atomic number: 83

Symbol: Bi

Category: post-transition metal (poor conductor …

Polonium

Atomic number: 84

Symbol: Po

Category: post-transition metal (but disputed properties)

Astatine

Atomic number: 85

Symbol: At

Category: halogen 

Density at 25°C: solid: density: …

Radon

Atomic number: 86

Symbol: Rn

Category: noble gas 

Density at 25°C: gas: density: …

Francium

Atomic number: 87

Symbol: Fr

Category: Alkali metal

Density at 25°C: solid: …

Radium

Atomic number: 88

Symbol: Ra

Category: Alkali earth metal

Density at 25°C: solid: …

Actinium

Atomic number: 89

Symbol: Ac

Category: actinide (transition metal)

Density at …

Thorium

Atomic number: 90

Symbol: Th

Category: actinide 

Density at 25°C: solid: density: …

Protactinium

Atomic number: 91

Symbol: Pa

Category: actinide 

Density at 25°C: solid: density: …

Uranium

Atomic number: 92

Symbol: U

Category: actinide 

Density at 25°C: solid: density: …

Neptunium

Atomic number: 93

Symbol: Np

Category: actinide 

Density at 25°C: solid: density: …

Plutonium

Atomic number: 94

Symbol: Pu

Category: actinide 

Density at 25°C: solid: density: …

Americium

Atomic number: 95

Symbol: Am

Category: actinide 

Density at 25°C: solid: density: …

Curium

Atomic number: 96

Symbol: Cm

Category: actinide 

Density at 25°C: solid: density: …

Berkelium

Atomic number: 97

Symbol: Bk

Category: actinide 

Density at 25°C: solid: density: …

Californium

Atomic number: 98

Symbol: Cf

Category: actinide 

Density at 25°C: solid: density: …

Einsteinium

Ivy_Mike_-_mushroom_cloud

Atomic number: 99

Symbol: Es

Category: actinide 

Density at 25°C: solid: density: …

Fermium

Atomic number: 100

Symbol: Fm

Category: actinide 

Density at 25°C: solid: density: …

Mendelevium

Atomic number: 101

Symbol: Md (Mv before the 1960s)

Category: actinide 

Density …

Nobelium

Atomic number: 102

Symbol: No 

Category: actinide 

Density at 25°C: solid:  …

Lawrencium

Atomic number: 103

Symbol: Lr (originally Lw) 

Category: actinide 

Density at …

Rutherfordium

Symbol: Rf

Category: (transition metal)

Density at 25°C: solid:  n/a

This is …

Dubnium

Symbol: Db

Category(transition metal)

Density at 25°C: solid:  n/a

This radioactive …

Seaborgium

Symbol: Sg

Category(transition metal)

Density at 25°C: solid:  n/a

This synthetic …

Bohrium

Symbol: Bh

Category(transition metal)

Density at 25°C: solid:  n/a

This artificially …

Hassium

Symbol: Hs

Category(transition metal)

Density at 25°C: solid:  n/a

This unstable …

Meitnerium

Symbol: Mt

Category(transition metal)

Density at 25°C: solid:  n/a

The longest …

Darmstadtium

Symbol: Ds

Category(transition metal)

Density at 25°C: solid:  n/a

The longest …

Roentgenium

Symbol: Rg

Category(transition metal)

Density at 25°C: solid:  n/a

For a heavy …

Copernicium

Symbol: Cn

Category(transition metal)

Density at 25°C: solid:  n/a

This synthetic …

Ununtrium

Symbol: Uut

Category(post transition metal)

Density at 25°C: solid:  n/a

Now …

Flerovium

Symbol: Fl

Category(post transition metal)

Density at 25°C: solid:  n/a

This …

Ununpentium

Symbol: Uup

Category(post transition metal)

Density at 25°C: solid:  n/a

Also …

Livermorium

Symbol: Lv

Category(post transition metal)

Density at 25°C: solid:  n/a

This …

Ununseptium

Symbol: Uus

Category(post transition metal)

Density at 25°C: solid:  n/a

This …

Ununoctium

This is the heaviest element number 118 so far created and discovered. It is …