All practice pages/Interatomic theory/Elements
Element 42, a transition metal
A metal that keeps its strength in the heat, named after lead by mistake, and needed by the bacteria that turn air into plant food.
Period 5, group 6. The other transition metals are tinted, and every cell opens its own article.
Molybdenum has 42 electrons, one for every proton, so the atom carries no charge. Below are the same 42 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s¹
Short form: [Kr] 4d⁵ 5s¹, where [Kr] stands for the 36 electrons krypton already has.
That list runs by shell. In the order the subshells fill it reads [Kr] 5s¹ 4d⁵, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 3 here is 3s² 3p⁶ 3d¹⁰, and 2 + 6 + 10 is 18.
Molybdenum sits in period 5 and has 5 shells. The period number counts the shells.
The outer shell holds 1 electron. Those are the ones molybdenum can lose, gain or share, so they are the ones that decide what it bonds with.
Like other transition metals, molybdenum loses its outer s electrons, and often some d electrons as well, to form positive ions, and it can form more than one kind.
Mined mostly as molybdenite (MoS₂) in China, Chile, Peru and the United States, often as a byproduct of copper mining. The Climax mine in Colorado was once the world's largest source.
Carl Wilhelm Scheele showed in 1778 that molybdenite was neither graphite nor a lead ore, as people had assumed, and Peter Jacob Hjelm isolated the metal in 1781. The name comes from the Greek molybdos, lead, because the soft black mineral had been mistaken for lead ore.
About 80% goes into steels and alloys that must stay strong and resist corrosion when hot, for tools, armor, pipelines and engine parts. Molybdenum disulfide is a slippery lubricant, molybdenum catalysts remove sulfur from fuels, and molybdenum-99 is the source of the technetium-99m used in medical scans. Nitrogen-fixing bacteria need molybdenum in their key enzyme.