Element 19 · Potassium (K)

Potassium Bohr model: diagram and electrons per shell

The potassium Bohr model shows a potassium atom (K) as a small nucleus with its electrons circling it in 4 shells: 2 in shell K, 8 in shell L, 8 in shell M and 1 in shell N. This page has a rotating 3D potassium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the potassium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of potassium (K), a simplified picture of a single potassium atom. Its nucleus holds 19 protons, and a neutral potassium atom has 19 electrons, arranged around it in 4 shells (2 in shell K, 8 in shell L, 8 in shell M and 1 in shell N).

K K · 21s² L · 82s² 2p⁶ M · 83s² 3p⁶ N · 14s¹

Potassium Bohr model diagram

Bohr model diagram of potassium: a nucleus of 19 protons with 19 electrons on 4 shells, 2 in shell K, 8 in shell L, 8 in shell M and 1 in shell N, each ring labelled with its shell letter. — The potassium 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, 8 in shell M and 1 in shell N).

Potassium electrons per shell

A neutral potassium atom has 19 electrons, one for each of its 19 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 8 in shell M and 1 in shell N.

Electrons in each shell of the potassium 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	8	18	3s² 3p⁶
N	4	1	32	4s¹

How the potassium Bohr model builds up, shell by shell

Watch the potassium 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, 8 in shell M and 1 in shell N) as it forms.

Animation of the potassium Bohr model being built: a nucleus of 19 protons appears first, then each shell grows in around it and takes its electrons, giving 19 electrons on 4 shells (2 in shell K, 8 in shell L, 8 in shell M and 1 in shell N). — The potassium 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, 8 in shell M and 1 in shell N. Protons are red, neutrons yellow and electrons blue.

How to draw the potassium Bohr model

Find the atomic number. Potassium has atomic number 19, so a neutral atom has 19 protons and 19 electrons.
Draw the nucleus. Put a circle in the centre and write K in it. The 19 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, 8 in shell M and 1 in shell N.
Check the total. 2 + 8 + 8 + 1 = 19, the atomic number, so every electron is accounted for.

Atomic data for the potassium Bohr model

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

Identity

Symbol: K
Atomic number: 19
Atomic mass: 39.0983 u
Family: Alkali Metals
Position: group 1, period 4
Block: s-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
Shorthand: [Ar] 4s¹
Electrons per shell: 2, 8, 8, 1
Outer-shell electrons: 1 in shell N

Ionisation energies

I₁: 418.8
I₂: 3052
I₃: 4420
I₄: 5877
I₅: 7975
I₆: 9590
I₇: 11343
I₈: 14944

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): 243
Empirical (pm): 220
Covalent (pm): 196
Van der Waals (pm): 275

Electronegativity and electron affinity

Electronegativity (Pauling): 0.82
Electron affinity (kJ/mol): 48.383

Oxidation states

Charges the element commonly takes in compounds.

Physical properties, abundance and history of potassium

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

Physical properties

Phase at room conditions: Solid
Appearance: Silvery gray
Melting point: 63.55°C (336.7 K)
Boiling point: 758.85°C (1032 K)
Density: 0.862 g/cm³
Thermal conductivity (W/m·K): 79
Specific heat (J/g·K): 0.757
Molar heat capacity (J/mol·K): 29.6
Heat of fusion (kJ/mol): 102.5
Heat of vaporisation (kJ/mol): 2.33

Abundance

Earth's crust (mg/kg): 20900
Oceans (mg/L): 399

Discovery

Discovered by: Humphry Davy
Year: 1807

Common compounds

Potassium Perchlorate ClKO4
Potassium Chloride ClK
Potassium Iodide IK
Potassium Bromide BrK
Potassium Permanganate KMnO4
Potassium Bromate BrKO3
Potassium Sorbate C6H7KO2
Potassium Nitrate KNO3

Compounds listed in the PubChem database.

Main isotopes of potassium

Isotopes of potassium share the same 19 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of potassium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
39	93.258 %	stable	–
40	0.012 %	1.248 Gy	β⁻, β⁺
41	6.73 %	stable	–
42	–	12.355 h	β⁻
43	–	22.3 h	β⁻
44	–	22.13 min	β⁻

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

More about potassium

Potassium on the periodic table – properties, isotopes, uses and the full potassium page.
Alkali Metals – all alkali metal elements and their trends.
Bohr model of every element – the Bohr model of all 118 elements.