Cr
Chromium
Element 24 · Transition metal
Chromium (Cr)
Chromium is a hard, shiny, steel-grey metal. It gives stainless steel its corrosion resistance and chrome plating its mirror finish.
- Transition metal
- Period 4
- Group 6
- d-block
- solid at room temperature
Key properties
- Atomic mass
- 51.996
- u
- Electron configuration
- [Ar] 3d5 4s1
- Melting point
- 1,906.9 °C
- 2,180 K
- Boiling point
- 2,670.9 °C
- 2,944 K
- Density
- 7.15 g/cm³
- Electronegativity
- 1.66
- Pauling
- Atomic radius
- 189 pm
- van der Waals
- 1st ionisation energy
- 6.767 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about chromium
- 01
Rubies are red and emeralds green because of traces of chromium.
- 02
Stainless steel contains at least 10.5% chromium.
- 03
Chromium is the hardest pure metal.
Applications
What is chromium used for?
- Stainless steel
- Chrome plating
- Pigments (chrome yellow, green)
- Leather tanning
History
Discovery & name origin
Discovered by
Year
Where
France
Name origin
Greek chroma, “colour” — its compounds are vividly coloured.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 24
- Atomic mass
- 51.996 u
- Group
- 6
- Period
- 4
- Block
- d-block
- Electron configuration
- [Ar] 3d5 4s1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s1 3d5
- Electrons per shell
- 2, 8, 13, 1
- Electronegativity (Pauling)
- 1.66
- Electron affinity
- 0.666 eV
- Atomic radius (van der Waals)
- 189 pm
- Stable isotopes
- 4
Oxidation states
Highlighted: common oxidation states (+6, +3, +2).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st652.9
- 2nd1,590.6
- 3rd2,987
- 4th4,743
- 5th6,702
- 6th8,744.9
- 7th15,455
- 8th17,820
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 2,180 K · 1,906.9 °C · 3,464.3 °F
- Boiling point
- 2,944 K · 2,670.9 °C · 4,839.5 °F
- Density
- 7.15 g/cm³
- Molar heat capacity
- 23.35 J/(mol·K)
- Appearance
- Silvery metallic
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Chromium questions
What is Cr on the periodic table?
Cr is the symbol for chromium, element 24 on the periodic table. It sits in group 6, period 4, in the transition metal category, and has an atomic mass of 51.996.
What is the atomic number of chromium?
Chromium has atomic number 24, so every chromium atom has 24 protons in its nucleus. Its symbol is Cr and its atomic mass is 51.996.
Who discovered chromium?
Chromium was discovered by Louis-Nicolas Vauquelin in 1797 (France). The name comes from Greek chroma, “colour” — its compounds are vividly coloured.
What is chromium used for?
Chromium is used for: stainless steel; chrome plating; pigments (chrome yellow, green); leather tanning.
Is chromium a metal?
Yes. Chromium is a transition metal, one of the metallic elements.
What is the electron configuration of chromium?
The electron configuration of chromium is [Ar] 3d5 4s1. Its 24 electrons are arranged in shells as 2, 8, 13, 1.