All practice pages/Interatomic theory/Elements
Element 27, a transition metal
Named after a mine goblin, it makes the deepest blue in glass and porcelain and keeps the batteries of phones and electric cars running.
Period 4, group 9. The other transition metals are tinted, and every cell opens its own article.
Cobalt has 27 electrons, one for every proton, so the atom carries no charge. Below are the same 27 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s²
Short form: [Ar] 3d⁷ 4s², where [Ar] stands for the 18 electrons argon already has.
That list runs by shell. In the order the subshells fill it reads [Ar] 4s² 3d⁷, 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 3d⁷, and 2 + 6 + 7 is 15.
Cobalt sits in period 4 and has 4 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones cobalt can lose, gain or share, so they are the ones that decide what it bonds with.
Like other transition metals, cobalt 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 almost entirely as a byproduct of copper and nickel. The Democratic Republic of the Congo produces about three quarters of the world's supply. A single cobalt atom sits at the center of vitamin B₁₂.
Georg Brandt showed around 1735 that the blue color of certain ores came from a new metal, the first metal discovered since ancient times. Miners had long blamed these ores, which gave off poisonous arsenic fumes when smelted, on the kobold, a mischievous goblin of German folklore, and the name stuck.
Lithium-ion battery cathodes now use the largest share. Cobalt also goes into superalloys for jet engine turbine blades, strong magnets, hard cutting tools, and catalysts that remove sulfur from fuels. Cobalt blue has colored glass and porcelain for centuries, and radioactive cobalt-60 treats cancer and sterilizes medical supplies.