Chromium

Symbol	Cr
Atomic number	24
Group	6 (Chromium group)
Period	4
Block	d
Classification	Transition Metal

Appearance	Silvery metallic
Color	Silver

Number of protons	24 p+
Number of neutrons	28 n0
Number of electrons	24 e-

From Wikipedia, the free encyclopediaChromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point.

Phase at STP	Solid
Density	7.19 g/cm3
Atomic weight	51.9962 u

Melting point	2180 K 1906.85 °C 3464.33 °F
Boiling point	2944 K 2670.85 °C 4839.53 °F
Heat of vaporization	339.5 kJ/mol

Electronegativity (Pauling Scale)	1.66
Electron affinity	65.21 kJ/mol
Oxidation states	−4, −2, −1, 0, +1, +2, +3, +4, +5, +6 (depending on the oxidation state, an acidic, basic, or amphoteric oxide)
Ionization energies	652.9 kJ/mol 1590.6 kJ/mol 2987 kJ/mol 4743 kJ/mol 6702 kJ/mol 8744.9 kJ/mol 15455 kJ/mol 17820 kJ/mol 20190 kJ/mol 23580 kJ/mol 26130 kJ/mol 28750 kJ/mol 34230 kJ/mol 37066 kJ/mol 97510 kJ/mol 105800 kJ/mol 114300 kJ/mol 125300 kJ/mol 134700 kJ/mol 144300 kJ/mol 157700 kJ/mol 166090 kJ/mol 721870 kJ/mol 761733 kJ/mol

Electron configuration Shorthand configuration	[Ar] 3d5 4s1
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 3d5 4s1
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 3d5 4s1
Electrons per shell	2, 8, 13, 1
Outer shell electrons	1
Valence electrons (incl. d)	6
Valency electrons	2
Bohr model	Figure: Shell diagram of Chromium (Cr) atom.
Orbital Diagram	1s 2s 2p 3s 3p 3d 4s

Discovery	Louis Nicolas Vauquelin (1794)
First isolation	Louis Nicolas Vauquelin (1797)
Discovery of chromium Chromium minerals as pigments came to the attention of the west in the eighteenth century. On 26 July 1761, Johann Gottlob Lehmann found an orange-red mineral in the Beryozovskoye mines in the Ural Mountains which he named Siberian red lead. In 1770, Peter Simon Pallas visited the same site as Lehmann and found a red lead mineral that was discovered to possess useful properties as a pigment in paints. After Pallas, the use of Siberian red lead as a paint pigment began to develop rapidly throughout the region. Crocoite would be the principal source of chromium in pigments until the discovery of chromite many years later. In 1794, Louis Nicolas Vauquelin received samples of crocoite ore. He produced chromium trioxide (CrO3) by mixing crocoite with hydrochloric acid. In 1797, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven, for which he is credited as the one who truly discovered the element.

Original word	chroma
Language of origin	Greek
Name source	Properties
Meaning	“Colour”
Naming The name is derived from the Greek word 'chroma', meaning color because it forms a variety of colorful compounds.

CAS Number	7440-47-3
ChemSpider ID	22412
EC number	231-157-5
PubChem CID Number	23976