Molybdenum (Mo)

Molybdenum properties

Atomic number

42

Atomic mass

95.95 u

Category

Transition metal

Group

6

Period

5

Block

d-block

State at room temp.

Solid

Electronegativity

2.16

Melting point

2,896 K (2,622.8 °C)

Boiling point

4,912 K (4,638.8 °C)

Density

10.28 g/cm³

Valence electrons

1

Common charges

+6

Oxidation states

+6

Atomic radius

209 pm

Ionization energy

7.092 eV

Electron affinity

0.746 eV

Radioactive

No, has stable isotopes

Discovered

1778

Molybdenum electron configuration

The electron configuration of Molybdenum (Mo) is [Kr] 4d5 5s1. Its 42 electrons are arranged in shells as 2, 8, 18, 13, 1.

Protons, neutrons and electrons in Molybdenum

A neutral Molybdenum atom has 42 protons and 42 electrons. Most Molybdenum atoms have about 54 neutrons: the atomic mass rounded to 96, minus the atomic number 42.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Molybdenum have?

1

Molybdenum has 1 valence electron, counting the electrons in its outermost s subshell. Like most transition metals, it can also use d electrons in bonding.

See every element: Periodic table with valence electrons

Molybdenum orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Molybdenum

95.95 g/mol

One mole of Molybdenum atoms (6.022 × 10²³ atoms) has a mass of 95.95 grams. Use this value to convert between grams and moles.

Molybdenum facts

• Its name comes from the Greek molybdos, meaning lead, because its ores were long mistaken for lead ores.
• Molybdenum is essential to life: nitrogen-fixing bacteria use it in nitrogenase, the enzyme that turns nitrogen from the air into ammonia.
• Molybdenum (Mo) has atomic number 42 and is a solid at room temperature. It was discovered in 1778.

Position in the periodic table

Molybdenum is element 42, in period 5 and group 6 of the periodic table, in the d-block.

All transition metals

Uses of Molybdenum

Molybdenum is used mostly in steel: adding it makes stainless and alloy steels stronger, tougher at high temperatures, and more resistant to corrosion, for pipelines, tools, and engine parts. Molybdenum disulfide is a slippery solid used as a dry lubricant and grease additive. Molybdenum catalysts help remove sulfur from crude oil during refining, and molybdenum-99 is the parent isotope that supplies hospitals with technetium-99m.

Who discovered Molybdenum?

Swedish chemist Carl Wilhelm Scheele showed in 1778 that the soft mineral molybdenite, until then confused with graphite, contained a new element. Peter Jacob Hjelm first isolated the metal in 1781 by heating its oxide with carbon.

Where does the name come from?

Molybdenum comes from the Greek molybdos, meaning 'lead'. Its main ore, molybdenite, was long confused with lead ores and with graphite, and all of these soft, dark minerals were called by similar names.

Discovery timeline