Element 37 · Rubidium (Rb)

Rubidium Bohr model: diagram and electrons per shell

The rubidium Bohr model shows a rubidium atom (Rb) as a small nucleus with its electrons circling it in 5 shells: 2 in shell K, 8 in shell L, 18 in shell M, 8 in shell N and 1 in shell O. This page has a rotating 3D rubidium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the rubidium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of rubidium (Rb), a simplified picture of a single rubidium atom. Its nucleus holds 37 protons, and a neutral rubidium atom has 37 electrons, arranged around it in 5 shells (2 in shell K, 8 in shell L, 18 in shell M, 8 in shell N and 1 in shell O).

Rb K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 84s² 4p⁶ O · 15s¹

Rubidium Bohr model diagram

Bohr model diagram of rubidium: a nucleus of 37 protons with 37 electrons on 5 shells, 2 in shell K, 8 in shell L, 18 in shell M, 8 in shell N and 1 in shell O, each ring labelled with its shell letter. — The rubidium 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, 8 in shell N and 1 in shell O).

Rubidium electrons per shell

A neutral rubidium atom has 37 electrons, one for each of its 37 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 8 in shell N and 1 in shell O.

Electrons in each shell of the rubidium 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	8	32	4s² 4p⁶
O	5	1	50	5s¹

How the rubidium Bohr model builds up, shell by shell

Watch the rubidium 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, 8 in shell N and 1 in shell O) as it forms.

Animation of the rubidium Bohr model being built: a nucleus of 37 protons appears first, then each shell grows in around it and takes its electrons, giving 37 electrons on 5 shells (2 in shell K, 8 in shell L, 18 in shell M, 8 in shell N and 1 in shell O). — The rubidium 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, 8 in shell N and 1 in shell O. Protons are red, neutrons yellow and electrons blue.

How to draw the rubidium Bohr model

Find the atomic number. Rubidium has atomic number 37, so a neutral atom has 37 protons and 37 electrons.
Draw the nucleus. Put a circle in the centre and write Rb in it. The 37 protons sit there with the neutrons.
Draw the shells. Sketch 5 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, 8 in shell N and 1 in shell O.
Check the total. 2 + 8 + 18 + 8 + 1 = 37, the atomic number, so every electron is accounted for.

Atomic data for the rubidium Bohr model

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

Identity

Symbol: Rb
Atomic number: 37
Atomic mass: 85.4678 u
Family: Alkali Metals
Position: group 1, period 5
Block: s-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹
Shorthand: [Kr] 5s¹
Electrons per shell: 2, 8, 18, 8, 1
Outer-shell electrons: 1 in shell O

Ionisation energies

I₁: 403
I₂: 2633
I₃: 3860
I₄: 5080
I₅: 6850
I₆: 8140
I₇: 9570
I₈: 13120

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): 265
Empirical (pm): 235
Covalent (pm): 210
Van der Waals (pm): 303

Electronegativity and electron affinity

Electronegativity (Pauling): 0.82
Electron affinity (kJ/mol): 46.884

Oxidation states

Charges the element commonly takes in compounds.

Physical properties, abundance and history of rubidium

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

Physical properties

Phase at room conditions: Solid
Appearance: Grey white
Melting point: 39.3°C (312.45 K)
Boiling point: 687.85°C (961 K)
Density: 1.532 g/cm³
Thermal conductivity (W/m·K): 58.2
Specific heat (J/g·K): 0.363
Molar heat capacity (J/mol·K): 31.06
Heat of fusion (kJ/mol): 2.2
Heat of vaporisation (kJ/mol): 75.8

Abundance

Earth's crust (mg/kg): 90
Oceans (mg/L): 0.12

Discovery

Discovered by: Robert Bunsen
Year: 1861

Common compounds

Rubidium Chloride ClRb
Rubidium bromide BrRb
Rubidium nitrate NO3Rb
Rubidium Rb
Rubidium Iodide IRb
Rubidium Chloride Rb-82 ClRb
Rubidium azide N3Rb
Rubidium hydroxide HORb

Compounds listed in the PubChem database.

Main isotopes of rubidium

Isotopes of rubidium share the same 37 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of rubidium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
81	–	4.572 h	β⁺
83	–	86.2 d	EC
84	–	32.82 d	β⁺, β⁻
85	72.17 %	stable	–
86	–	18.645 d	β⁻, EC
87	27.83 %	49.7 Gy	β⁻

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

More about rubidium

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