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Molybdenum

Element 42 · Transition metal

Specimen

Atomic number
42
Atomic mass
95.95
State at room temperature
Solid
Melting point
2,623 °C
Boiling point
4,639 °C
Density
10.2 g/cm³
Discovered
1778

Atomic mass from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Your body needs it. Molybdenum, as molybdate in food, is a nutrient that some enzymes need. EFSA sets an adequate intake of 65 micrograms a day for adults. The RSC says larger amounts are toxic. 34

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The atom

Mo
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 13
5 (O) outermost 1
Total42

Configuration [Kr] 4d⁵ 5s¹

4d ↑ ↑ ↑ ↑ ↑
5s ↑
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 42 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Kr core, with one arrow per electron.

Related elements

Group 6
Cr Chromium W Tungsten Sg Seaborgium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Abridged Standard Atomic Weights 2024 .

    The atomic mass shown for the 84 elements that have a standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    European Food Safety Authority (EFSA), 2017. Dietary Reference Values for nutrients. Summary report , Section 4.5 (iodine) and 4.9 (molybdenum).

    • Molybdenum is an essential component of certain enzymes ... An AI of 65 µg/day is proposed for adult men and women
  4. 4

    Royal Society of Chemistry, 2026. Molybdenum - Element information, properties and uses .

    • Although it is toxic in anything other than small quantities, molybdenum is an essential element for animals and plants.
  5. 5

    National Institute of Standards and Technology (NIST), 2026. Atomic Weights and Isotopic Compositions for All Elements .

    Isotopic composition of each element; the most abundant isotope sets the neutron count in the nucleus view.