Element 42 · Molybdenum (Mo)

Molybdenum Bohr model: diagram and electrons per shell

The molybdenum Bohr model shows a molybdenum atom (Mo) as a small nucleus with its electrons circling it in 5 shells: 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 1 in shell O. This page has a rotating 3D molybdenum Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the molybdenum Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of molybdenum (Mo), a simplified picture of a single molybdenum atom. Its nucleus holds 42 protons, and a neutral molybdenum atom has 42 electrons, arranged around it in 5 shells (2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 1 in shell O).

Mo K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 134s² 4p⁶ 4d⁵ O · 15s¹

Molybdenum Bohr model diagram

Bohr model diagram of molybdenum: a nucleus of 42 protons with 42 electrons on 5 shells, 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 1 in shell O, each ring labelled with its shell letter. — The molybdenum 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, 13 in shell N and 1 in shell O).

Molybdenum electrons per shell

A neutral molybdenum atom has 42 electrons, one for each of its 42 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 1 in shell O.

Electrons in each shell of the molybdenum 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	13	32	4s² 4p⁶ 4d⁵
O	5	1	50	5s¹

How the molybdenum Bohr model builds up, shell by shell

Watch the molybdenum 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, 13 in shell N and 1 in shell O) as it forms.

Animation of the molybdenum Bohr model being built: a nucleus of 42 protons appears first, then each shell grows in around it and takes its electrons, giving 42 electrons on 5 shells (2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 1 in shell O). — The molybdenum 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, 13 in shell N and 1 in shell O. Protons are red, neutrons yellow and electrons blue.

How to draw the molybdenum Bohr model

Find the atomic number. Molybdenum has atomic number 42, so a neutral atom has 42 protons and 42 electrons.
Draw the nucleus. Put a circle in the centre and write Mo in it. The 42 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, 13 in shell N and 1 in shell O.
Check the total. 2 + 8 + 18 + 13 + 1 = 42, the atomic number, so every electron is accounted for.

Atomic data for the molybdenum Bohr model

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

Identity

Symbol: Mo
Atomic number: 42
Atomic mass: 95.951 u
Family: Transition Metals
Position: group 6, period 5
Block: d-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁵
Shorthand: [Kr] 4d⁵ 5s¹
Electrons per shell: 2, 8, 18, 13, 1
Outer-shell electrons: 1 in shell O

Ionisation energies

I₁: 684.3
I₂: 1560
I₃: 2618
I₄: 4480
I₅: 5257
I₆: 6640.8
I₇: 12125
I₈: 13860

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): 190
Empirical (pm): 145
Covalent (pm): 138

Electronegativity and electron affinity

Electronegativity (Pauling): 2.16
Electron affinity (kJ/mol): 72.1

Oxidation states

+4 +6

Charges the element commonly takes in compounds.

Physical properties, abundance and history of molybdenum

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

Physical properties

Phase at room conditions: Solid
Appearance: Gray metallic
Melting point: 2622.85°C (2896 K)
Boiling point: 4638.85°C (4912 K)
Density: 10.28 g/cm³
Specific heat (J/g·K): 0.251
Molar heat capacity (J/mol·K): 24.06
Heat of fusion (kJ/mol): 28
Heat of vaporisation (kJ/mol): 590

Abundance

Earth's crust (mg/kg): 1.2
Oceans (mg/L): 0.01

Discovery

Discovered by: Carl Wilhelm Scheele
Year: 1778

Common compounds

Molybdenum Mo
Molybdenum trioxide MoO3
COBALT MOLYBDENUM OXIDE (CoMoO4) CoMoO4
Molybdenum disulfide MoS2
Sodium Molybdate MoNa2O4
Molybdic acid H2MoO4
Sodium molybdate dihydrate H4MoNa2O6
Lead molybdate MoO4Pb

Compounds listed in the PubChem database.

Main isotopes of molybdenum

Isotopes of molybdenum share the same 42 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of molybdenum: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
92	14.649 %	stable	2β⁺
95	15.873 %	stable	–
96	16.673 %	stable	–
97	9.582 %	stable	–
98	24.292 %	stable	2β⁻
100	9.744 %	7.07 Ey	2β⁻

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

More about molybdenum

Molybdenum on the periodic table – properties, isotopes, uses and the full molybdenum page.
Transition Metals – all transition metal elements and their trends.
Bohr model of every element – the Bohr model of all 118 elements.