Element 56 · Barium (Ba)

Barium Bohr model: diagram and electrons per shell

The barium Bohr model shows a barium atom (Ba) as a small nucleus with its electrons circling it in 6 shells: 2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P. This page has a rotating 3D barium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the barium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of barium (Ba), a simplified picture of a single barium atom. Its nucleus holds 56 protons, and a neutral barium atom has 56 electrons, arranged around it in 6 shells (2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P).

Ba K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 184s² 4p⁶ 4d¹⁰ O · 85s² 5p⁶ P · 26s²

Barium Bohr model diagram

Bohr model diagram of barium: a nucleus of 56 protons with 56 electrons on 6 shells, 2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P, each ring labelled with its shell letter. — The barium Bohr model drawn flat: each ring is a shell, labelled with its letter, and every dot is an electron (2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P).

Barium electrons per shell

A neutral barium atom has 56 electrons, one for each of its 56 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P.

Electrons in each shell of the barium Bohr model
Shell	Shell number (n)	Electrons	Most it can hold (2n²)	Subshells
K	1	2	2	1s²
L	2	8	8	2s² 2p⁶
M	3	18	18	3s² 3p⁶ 3d¹⁰
N	4	18	32	4s² 4p⁶ 4d¹⁰
O	5	8	50	5s² 5p⁶
P	6	2	72	6s²

How the barium Bohr model builds up, shell by shell

Watch the barium 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, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P) as it forms.

Animation of the barium Bohr model being built: a nucleus of 56 protons appears first, then each shell grows in around it and takes its electrons, giving 56 electrons on 6 shells (2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P). — The barium Bohr model built up in six seconds: the nucleus first, then each shell with its electrons, ending with 2 in shell K, 8 in shell L, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P. Protons are red, neutrons yellow and electrons blue.

How to draw the barium Bohr model

Find the atomic number. Barium has atomic number 56, so a neutral atom has 56 protons and 56 electrons.
Draw the nucleus. Put a circle in the centre and write Ba in it. The 56 protons sit there with the neutrons.
Draw the shells. Sketch 6 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, 18 in shell M, 18 in shell N, 8 in shell O and 2 in shell P.
Check the total. 2 + 8 + 18 + 18 + 8 + 2 = 56, the atomic number, so every electron is accounted for.

Atomic data for the barium Bohr model

The numbers behind the barium Bohr model, grouped by topic. Radii are in picometres (pm) and energies in kilojoules per mole (kJ/mol).

Identity

Symbol: Ba
Atomic number: 56
Atomic mass: 137.3277 u
Family: Alkaline Earth Metals
Position: group 2, period 6
Block: s-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s²
Shorthand: [Xe] 6s²
Electrons per shell: 2, 8, 18, 18, 8, 2
Outer-shell electrons: 2 in shell P

Ionisation energies

I₁: 502.9
I₂: 965.2
I₃: 3600

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): 253
Empirical (pm): 215
Covalent (pm): 196
Van der Waals (pm): 268

Electronegativity and electron affinity

Electronegativity (Pauling): 0.89
Electron affinity (kJ/mol): 13.954

Oxidation states

Charges the element commonly takes in compounds.

Physical properties, abundance and history of barium

Bulk properties of barium, how common it is, who discovered it and some of its compounds.

Physical properties

Phase at room conditions: Solid
Melting point: 726.85°C (1000 K)
Boiling point: 1844.85°C (2118 K)
Density: 3.51 g/cm³
Specific heat (J/g·K): 0.204
Molar heat capacity (J/mol·K): 28.07
Heat of fusion (kJ/mol): 7.66
Heat of vaporisation (kJ/mol): 142

Abundance

Earth's crust (mg/kg): 425
Oceans (mg/L): 0.013

Discovery

Discovered by: Carl Wilhelm Scheele
Year: 1808

Common compounds

Barium chromate BaCrO4
Barium Sulfate BaO4S
Barium nitrate BaN2O6
Barium Ba
Barium acetate C4H6BaO4
D&C Red 9 C34H24BaCl2N4O8S2
Barium hexafluorosilicate BaF6Si
Barium peroxide BaO2

Compounds listed in the PubChem database.

Main isotopes of barium

Isotopes of barium share the same 56 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of barium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
130	0.11 %	stable	2β⁺
134	2.42 %	stable	–
135	6.59 %	stable	–
136	7.85 %	stable	–
137	11.23 %	stable	–
138	71.7 %	stable	–

α = alpha decay, β⁻ = beta-minus, β⁺ = beta-plus, EC = electron capture, SF = spontaneous fission, p / n = proton / neutron emission.

More about barium

Barium on the periodic table – properties, isotopes, uses and the full barium page.
Alkaline Earth Metals – all alkaline earth metal elements and their trends.
Bohr model of every element – the Bohr model of all 118 elements.