Chromium (Cr)

Chromium properties

Atomic number

24

Atomic mass

51.996 u

Category

Transition metal

Group

6

Period

4

Block

d-block

State at room temp.

Solid

Electronegativity

1.66

Melting point

2,180 K (1,906.8 °C)

Boiling point

2,944 K (2,670.8 °C)

Density

7.19 g/cm³

Valence electrons

1

Common charges

+2, +3, +6

Oxidation states

+6, +3, +2

Atomic radius

189 pm

Ionization energy

6.767 eV

Electron affinity

0.666 eV

Radioactive

No, has stable isotopes

Discovered

1797

Chromium electron configuration

The electron configuration of Chromium (Cr) is [Ar] 3d5 4s1. Its 24 electrons are arranged in shells as 2, 8, 13, 1.

Protons, neutrons and electrons in Chromium

A neutral Chromium atom has 24 protons and 24 electrons. Most Chromium atoms have about 28 neutrons: the atomic mass rounded to 52, minus the atomic number 24.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Chromium have?

1

Chromium has 1 valence electron, counting the electrons in its outermost s subshell. Like most transition metals, it can also use d electrons in bonding.

See every element: Periodic table with valence electrons

Chromium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Chromium

51.996 g/mol

One mole of Chromium atoms (6.022 × 10²³ atoms) has a mass of 51.996 grams. Use this value to convert between grams and moles.

Compounds containing Chromium

Chromium facts

• Traces of chromium give rubies their red color and many emeralds their green.
• The name chromium comes from the Greek word chroma, meaning color, because its compounds come in so many vivid colors.
• Chromium (Cr) has atomic number 24 and is a solid at room temperature. It was discovered in 1797.

Position in the periodic table

Chromium is element 24, in period 4 and group 6 of the periodic table, in the d-block.

All transition metals

Uses of Chromium

Chromium is essential to stainless steel, which must contain at least about 10.5% chromium; the chromium forms a thin oxide layer that stops rust. Chrome plating gives car trim, taps and tools a shiny, hard-wearing finish. Chromium compounds are used to tan most of the world's leather and to make pigments such as chromium oxide green.

Who discovered Chromium?

French chemist Louis-Nicolas Vauquelin discovered chromium in 1797 in crocoite, a bright orange-red mineral from Siberia. He isolated the metal the following year by heating its oxide with charcoal.

Where does the name come from?

Chromium comes from the Greek chroma, meaning 'color'. Louis-Nicolas Vauquelin chose the name in 1797 because chromium compounds come in a wide range of vivid colors, from red and orange to green.

Discovery timeline