Molybdenum (Mo)
Molybdenum is element 42, a transition metal in period 5, group 6 of the periodic table. At room temperature it is a solid.
Electron configuration [Kr] 4d5 5s1
Electrons per shell 2, 8, 18, 13, 1
Molybdenum data
| Atomic number | 42 |
|---|---|
| Symbol | Mo |
| Atomic mass | 95.96 u |
| Category | Transition metal |
| Group | 6 |
| Period | 5 |
| Block | d |
| State at 25 °C | solid |
| Melting point | 2896 K (2622.9 °C) |
| Boiling point | 4912 K (4638.9 °C) |
| Density | 10.28 g/cm³ |
| Electronegativity (Pauling) | 2.16 |
| Atomic radius | 145 pm |
| 1st ionization energy | 684 kJ/mol |
| Electron affinity | -72 kJ/mol |
| Oxidation states | -2, -1, +1, +2, +3, +4, +5, +6 |
| Common ion charge | 6+ |
| Discovered | 1778 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through molybdenum’s configuration and its ions →
Where molybdenum sits
Molybdenum belongs to the transition metals. Its Pauling electronegativity of 2.16 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Molybdenum FAQ
What is the electron configuration of molybdenum?
Molybdenum (Z = 42) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s1. In noble-gas shorthand that is [Kr] 4d5 5s1. This is an exception to the simple Aufbau prediction (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d4 5s2); a half-filled or filled subshell lowers the energy.
How many valence electrons does molybdenum have?
6 (1 outer s + 5 d electrons; 1 in the outermost shell).
What is the atomic mass of molybdenum?
The standard atomic weight of molybdenum is 95.96 u, so one mole weighs 95.96 g.
Is molybdenum a metal?
Yes. Molybdenum is a transition metal.
What is the charge of a molybdenum ion?
Molybdenum most commonly forms Mo6+.