Element 24 · Chromium (Cr)
Chromium Bohr model: diagram and electrons per shell
The chromium Bohr model shows a chromium atom (Cr) as a small nucleus with its electrons circling it in 4 shells: 2 in shell K, 8 in shell L, 13 in shell M and 1 in shell N. This page has a rotating 3D chromium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.
Rotate the chromium Bohr model in 3D
Drag to orbit, scroll to zoom.
This is a Bohr model of chromium (Cr), a simplified picture of a single chromium atom. Its nucleus holds 24 protons, and a neutral chromium atom has 24 electrons, arranged around it in 4 shells (2 in shell K, 8 in shell L, 13 in shell M and 1 in shell N).
Chromium Bohr model diagram
Chromium electrons per shell
A neutral chromium atom has 24 electrons, one for each of its 24 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 13 in shell M and 1 in shell N.
| Shell | Shell number (n) | Electrons | Most it can hold (2n²) | Subshells |
|---|---|---|---|---|
| K | 1 | 2 | 2 | 1s2 |
| L | 2 | 8 | 8 | 2s2 2p6 |
| M | 3 | 13 | 18 | 3s2 3p6 3d5 |
| N | 4 | 1 | 32 | 4s1 |
How the chromium Bohr model builds up, shell by shell
Watch the chromium Bohr model come together: the nucleus first, then each shell in turn, from the innermost outwards, with its electrons joining the ring. The legend names every shell and counts its electrons, so you can read off the arrangement (2 in shell K, 8 in shell L, 13 in shell M and 1 in shell N) as it forms.
How to draw the chromium Bohr model
- Find the atomic number. Chromium has atomic number 24, so a neutral atom has 24 protons and 24 electrons.
- Draw the nucleus. Put a circle in the centre and write Cr in it. The 24 protons sit there with the neutrons.
- Draw the shells. Sketch 4 shells as rings around the nucleus. A shell holds at most 2n² electrons: 2 in the first, 8 in the second, 18 in the third and 32 in the fourth.
- Place the electrons. Fill from the inside out: 2 in shell K, 8 in shell L, 13 in shell M and 1 in shell N.
- Check the total. 2 + 8 + 13 + 1 = 24, the atomic number, so every electron is accounted for.
Atomic data for the chromium Bohr model
The numbers behind the chromium Bohr model, grouped by topic. Radii are in picometres (pm) and energies in kilojoules per mole (kJ/mol).
Identity
- Symbol
- Cr
- Atomic number
- 24
- Atomic mass
- 51.9962 u
- Family
- Transition Metals
- Position
- group 6, period 4
- Block
- d-block
Electron configuration
- Full
- 1s2 2s2 2p6 3s2 3p6 4s1 3d5
- Shorthand
- [Ar] 3d5 4s1
- Electrons per shell
- 2, 8, 13, 1
- Outer-shell electrons
- 1 in shell N
Ionisation energies
- I₁
- 652.9
- I₂
- 1590.6
- I₃
- 2987
- I₄
- 4743
- I₅
- 6702
- I₆
- 8744.9
- I₇
- 15455
- I₈
- 17820
Energy to remove each electron in turn (kJ/mol). A sharp jump means the next electron comes from an inner shell.
Atomic radii
- Calculated (pm)
- 166
- Empirical (pm)
- 140
- Covalent (pm)
- 122
Electronegativity and electron affinity
- Electronegativity (Pauling)
- 1.66
- Electron affinity (kJ/mol)
- 65.21
Oxidation states
+3 +6
Charges the element commonly takes in compounds.
Physical properties, abundance and history of chromium
Bulk properties of chromium, how common it is, who discovered it and some of its compounds.
Physical properties
- Phase at room conditions
- Solid
- Appearance
- Silvery metallic
- Melting point
- 1906.85°C (2180 K)
- Boiling point
- 2670.85°C (2944 K)
- Density
- 7.19 g/cm³
- Thermal conductivity (W/m·K)
- 93.9
- Specific heat (J/g·K)
- 0.449
- Molar heat capacity (J/mol·K)
- 23.35
- Heat of fusion (kJ/mol)
- 21
- Heat of vaporisation (kJ/mol)
- 342
Abundance
- Earth's crust (mg/kg)
- 102
- Oceans (mg/L)
- 0
Discovery
- Discovered by
- Louis Nicolas Vauquelin
- Year
- 1797
Common compounds
- Sodium Chromate CrNa2O4
- Zinc Chromate CrO4Zn
- Chromium Cr
- Chromic Acid CrH2O4
- Barium chromate BaCrO4
- Chromium Trioxide CrO3
- Lead Chromate CrO4Pb
- Chromium(III) acetate C6H9CrO6
Compounds listed in the PubChem database.
Main isotopes of chromium
Isotopes of chromium share the same 24 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.
| Mass number | Natural abundance | Half-life | Decay |
|---|---|---|---|
| 48 | – | 21.56 h | β⁺ |
| 50 | 4.345 % | stable | 2β⁺ |
| 51 | – | 27.701 d | EC |
| 52 | 83.789 % | stable | – |
| 53 | 9.501 % | stable | – |
| 54 | 2.365 % | stable | – |
α = alpha decay, β⁻ = beta-minus, β⁺ = beta-plus, EC = electron capture, SF = spontaneous fission, p / n = proton / neutron emission.
More about chromium
- Chromium on the periodic table – properties, isotopes, uses and the full chromium page.
- Transition Metals – all transition metal elements and their trends.
- Bohr model of every element – the Bohr model of all 118 elements.