Element 61 · Promethium (Pm)

Promethium Bohr model: diagram and electrons per shell

The promethium Bohr model shows a promethium atom (Pm) as a small nucleus with its electrons circling it in 6 shells: 2 in shell K, 8 in shell L, 18 in shell M, 23 in shell N, 8 in shell O and 2 in shell P. This page has a rotating 3D promethium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the promethium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of promethium (Pm), a simplified picture of a single promethium atom. Its nucleus holds 61 protons, and a neutral promethium atom has 61 electrons, arranged around it in 6 shells (2 in shell K, 8 in shell L, 18 in shell M, 23 in shell N, 8 in shell O and 2 in shell P).

Pm K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 234s² 4p⁶ 4d¹⁰ 4f⁵ O · 85s² 5p⁶ P · 26s²

Promethium Bohr model diagram

Bohr model diagram of promethium: a nucleus of 61 protons with 61 electrons on 6 shells, 2 in shell K, 8 in shell L, 18 in shell M, 23 in shell N, 8 in shell O and 2 in shell P, each ring labelled with its shell letter. — The promethium 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, 23 in shell N, 8 in shell O and 2 in shell P).

Promethium electrons per shell

A neutral promethium atom has 61 electrons, one for each of its 61 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 23 in shell N, 8 in shell O and 2 in shell P.

Electrons in each shell of the promethium 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	23	32	4s² 4p⁶ 4d¹⁰ 4f⁵
O	5	8	50	5s² 5p⁶
P	6	2	72	6s²

How the promethium Bohr model builds up, shell by shell

Watch the promethium 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, 23 in shell N, 8 in shell O and 2 in shell P) as it forms.

Animation of the promethium Bohr model being built: a nucleus of 61 protons appears first, then each shell grows in around it and takes its electrons, giving 61 electrons on 6 shells (2 in shell K, 8 in shell L, 18 in shell M, 23 in shell N, 8 in shell O and 2 in shell P). — The promethium 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, 23 in shell N, 8 in shell O and 2 in shell P. Protons are red, neutrons yellow and electrons blue.

How to draw the promethium Bohr model

Find the atomic number. Promethium has atomic number 61, so a neutral atom has 61 protons and 61 electrons.
Draw the nucleus. Put a circle in the centre and write Pm in it. The 61 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, 23 in shell N, 8 in shell O and 2 in shell P.
Check the total. 2 + 8 + 18 + 23 + 8 + 2 = 61, the atomic number, so every electron is accounted for.

Atomic data for the promethium Bohr model

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

Identity

Symbol: Pm
Atomic number: 61
Atomic mass: [145] u
Family: Lanthanides
Position: period 6 of the f-block
Block: f-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁵
Shorthand: [Xe] 4f⁵ 6s²
Electrons per shell: 2, 8, 18, 23, 8, 2
Outer-shell electrons: 2 in shell P

Ionisation energies

I₁: 540
I₂: 1050
I₃: 2150
I₄: 3970

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): 205
Empirical (pm): 185
Covalent (pm): 173

Electronegativity and electron affinity

Electronegativity (Pauling): 1.13
Electron affinity (kJ/mol): 12.45

Oxidation states

Charges the element commonly takes in compounds.

Physical properties, abundance and history of promethium

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

Physical properties

Phase at room conditions: Solid
Appearance: Metallic
Melting point: 1041.85°C (1315 K)
Boiling point: 2999.85°C (3273 K)
Density: 7.26 g/cm³
Thermal conductivity (W/m·K): 17.9

Discovery

Discovered by: Chien Shiung Wu
Year: 1945
Named by: Isotopes of promethium

Common compounds

Promethium Pm
Promethium trichloride Cl3Pm
Promethium-147 Pm
Promethium-149 Pm
Promethium, isotope of mass 148 Pm
Promethium-143 Pm
Promethium-145 Pm
(~146~Pm)Promethium Pm

Compounds listed in the PubChem database.

Main isotopes of promethium

Isotopes of promethium share the same 61 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of promethium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
143	–	265 d	EC, e⁺
144	–	363 d	EC, e⁺
145	–	17.7 y	EC, α
146	–	5.53 y	EC, β⁻
147	–	2.623 y	β⁻
148	–	5.368 d	β⁻

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

More about promethium

Promethium on the periodic table – properties, isotopes, uses and the full promethium page.
Lanthanides – all lanthanide elements and their trends.
Bohr model of every element – the Bohr model of all 118 elements.