Element 87 · Francium (Fr)

Francium Bohr model: diagram and electrons per shell

The francium Bohr model shows a francium atom (Fr) as a small nucleus with its electrons circling it in 7 shells: 2 in shell K, 8 in shell L, 18 in shell M, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q. This page has a rotating 3D francium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the francium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of francium (Fr), a simplified picture of a single francium atom. Its nucleus holds 87 protons, and a neutral francium atom has 87 electrons, arranged around it in 7 shells (2 in shell K, 8 in shell L, 18 in shell M, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q).

Fr K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 324s² 4p⁶ 4d¹⁰ 4f¹⁴ O · 185s² 5p⁶ 5d¹⁰ P · 86s² 6p⁶ Q · 17s¹

Francium Bohr model diagram

Bohr model diagram of francium: a nucleus of 87 protons with 87 electrons on 7 shells, 2 in shell K, 8 in shell L, 18 in shell M, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q, each ring labelled with its shell letter. — The francium 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, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q).

Francium electrons per shell

A neutral francium atom has 87 electrons, one for each of its 87 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q.

Electrons in each shell of the francium 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	32	32	4s² 4p⁶ 4d¹⁰ 4f¹⁴
O	5	18	50	5s² 5p⁶ 5d¹⁰
P	6	8	72	6s² 6p⁶
Q	7	1	98	7s¹

How the francium Bohr model builds up, shell by shell

Watch the francium 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, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q) as it forms.

Animation of the francium Bohr model being built: a nucleus of 87 protons appears first, then each shell grows in around it and takes its electrons, giving 87 electrons on 7 shells (2 in shell K, 8 in shell L, 18 in shell M, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q). — The francium 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, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q. Protons are red, neutrons yellow and electrons blue.

How to draw the francium Bohr model

Find the atomic number. Francium has atomic number 87, so a neutral atom has 87 protons and 87 electrons.
Draw the nucleus. Put a circle in the centre and write Fr in it. The 87 protons sit there with the neutrons.
Draw the shells. Sketch 7 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, 32 in shell N, 18 in shell O, 8 in shell P and 1 in shell Q.
Check the total. 2 + 8 + 18 + 32 + 18 + 8 + 1 = 87, the atomic number, so every electron is accounted for.

Atomic data for the francium Bohr model

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

Identity

Symbol: Fr
Atomic number: 87
Atomic mass: [223] u
Family: Alkali Metals
Position: group 1, period 7
Block: s-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s¹
Shorthand: [Rn] 7s¹
Electrons per shell: 2, 8, 18, 32, 18, 8, 1
Outer-shell electrons: 1 in shell Q

Ionisation energies

I₁: 380

Energy to remove each electron in turn (kJ/mol). A sharp jump means the next electron comes from an inner shell.

Atomic radii

Van der Waals (pm): 348

Electronegativity and electron affinity

Electronegativity (Pauling): 0.79
Electron affinity (kJ/mol): 46.89

Oxidation states

Charges the element commonly takes in compounds.

Physical properties, abundance and history of francium

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

Physical properties

Phase at room conditions: Solid
Melting point: 26.85°C (300 K)
Boiling point: 676.85°C (950 K)
Density: 1.87 g/cm³
Heat of fusion (kJ/mol): 15

Discovery

Discovered by: Marguerite Perey
Year: 1939

Common compounds

Francium Fr
Francium, isotope of mass 223 Fr
Francium-222 Fr
Francium-221 Fr
Francium-219 Fr
Francium-220 Fr
Cesium;francium CsFr
CID 101943069 FrH2

Compounds listed in the PubChem database.

Main isotopes of francium

Isotopes of francium share the same 87 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of francium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
212	–	20 min	β⁺, α
221	–	4.801 min	α, β⁻, 14C
222	–	14.2 min	β⁻
223	–	22 min	β⁻, α
224	–	3.33 min	β⁻
225	–	3.95 min	β⁻

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

More about francium

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