Element 65 · Terbium (Tb)

Terbium Bohr model: diagram and electrons per shell

The terbium Bohr model shows a terbium atom (Tb) as a small nucleus with its electrons circling it in 6 shells: 2 in shell K, 8 in shell L, 18 in shell M, 27 in shell N, 8 in shell O and 2 in shell P. This page has a rotating 3D terbium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the terbium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of terbium (Tb), a simplified picture of a single terbium atom. Its nucleus holds 65 protons, and a neutral terbium atom has 65 electrons, arranged around it in 6 shells (2 in shell K, 8 in shell L, 18 in shell M, 27 in shell N, 8 in shell O and 2 in shell P).

Tb K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 274s² 4p⁶ 4d¹⁰ 4f⁹ O · 85s² 5p⁶ P · 26s²

Terbium Bohr model diagram

Bohr model diagram of terbium: a nucleus of 65 protons with 65 electrons on 6 shells, 2 in shell K, 8 in shell L, 18 in shell M, 27 in shell N, 8 in shell O and 2 in shell P, each ring labelled with its shell letter. — The terbium 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, 27 in shell N, 8 in shell O and 2 in shell P).

Terbium electrons per shell

A neutral terbium atom has 65 electrons, one for each of its 65 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 27 in shell N, 8 in shell O and 2 in shell P.

Electrons in each shell of the terbium 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	27	32	4s² 4p⁶ 4d¹⁰ 4f⁹
O	5	8	50	5s² 5p⁶
P	6	2	72	6s²

How the terbium Bohr model builds up, shell by shell

Watch the terbium 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, 27 in shell N, 8 in shell O and 2 in shell P) as it forms.

Animation of the terbium Bohr model being built: a nucleus of 65 protons appears first, then each shell grows in around it and takes its electrons, giving 65 electrons on 6 shells (2 in shell K, 8 in shell L, 18 in shell M, 27 in shell N, 8 in shell O and 2 in shell P). — The terbium 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, 27 in shell N, 8 in shell O and 2 in shell P. Protons are red, neutrons yellow and electrons blue.

How to draw the terbium Bohr model

Find the atomic number. Terbium has atomic number 65, so a neutral atom has 65 protons and 65 electrons.
Draw the nucleus. Put a circle in the centre and write Tb in it. The 65 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, 27 in shell N, 8 in shell O and 2 in shell P.
Check the total. 2 + 8 + 18 + 27 + 8 + 2 = 65, the atomic number, so every electron is accounted for.

Atomic data for the terbium Bohr model

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

Identity

Symbol: Tb
Atomic number: 65
Atomic mass: 158.9254 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 4f⁹
Shorthand: [Xe] 4f⁹ 6s²
Electrons per shell: 2, 8, 18, 27, 8, 2
Outer-shell electrons: 2 in shell P

Ionisation energies

I₁: 565.8
I₂: 1110
I₃: 2114
I₄: 3839

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): 225
Empirical (pm): 175
Covalent (pm): 168

Electronegativity and electron affinity

Electronegativity (Pauling): 1.1
Electron affinity (kJ/mol): 112.4

Oxidation states

Charges the element commonly takes in compounds.

Physical properties, abundance and history of terbium

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

Physical properties

Phase at room conditions: Solid
Appearance: Silvery white
Melting point: 1355.85°C (1629 K)
Boiling point: 3122.85°C (3396 K)
Density: 8.23 g/cm³
Thermal conductivity (W/m·K): 11.1
Specific heat (J/g·K): 0.182
Molar heat capacity (J/mol·K): 28.91
Heat of vaporisation (kJ/mol): 389

Abundance

Earth's crust (mg/kg): 1.2
Oceans (mg/L): 0

Discovery

Discovered by: Carl Gustaf Mosander
Year: 1843

Common compounds

Terbium Tb
Terbium chloride Cl3Tb
Terbium bromide (TbBr3) Br3Tb
Terbium nitrate N3O9Tb
Terbium nitride (TbN) NTb
Terbium fluoride F3Tb
Terbium iodide (TbI3) I3Tb
Terbium oxide OTb-2

Compounds listed in the PubChem database.

Main isotopes of terbium

Isotopes of terbium share the same 65 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of terbium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
156	–	5.35 d	β⁺, β⁻
157	–	71 y	EC
158	–	180 y	β⁺, β⁻
159	100 %	stable	–
160	–	72.3 d	β⁻
161	–	6.948 d	β⁻

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

More about terbium

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