All practice pages/Interatomic theory/Elements
Element 21, a transition metal
A light, rare metal that Mendeleev predicted before anyone found it, now used to strengthen the aluminum in bike frames and baseball bats.
Period 4, group 3. The other transition metals are tinted, and every cell opens its own article.
Scandium has 21 electrons, one for every proton, so the atom carries no charge. Below are the same 21 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²
Short form: [Ar] 3d¹ 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 3d¹, 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 3d¹, and 2 + 6 + 1 is 9.
Scandium sits in period 4 and has 4 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones scandium can lose, gain or share, so they are the ones that decide what it bonds with.
Scandium gives up its two 4s electrons and its single 3d electron to form Sc³⁺, the only ion it commonly makes, so it behaves more like aluminum than like a typical transition metal.
More common in the crust than lead, but spread so thinly that there are few ores worth mining. It is recovered mostly as a byproduct of processing other ores, in China, Russia and the Philippines.
Lars Fredrik Nilson found it in 1879 in the minerals euxenite and gadolinite and named it after Scandinavia. Per Teodor Cleve soon pointed out that it was the eka-boron Mendeleev had predicted in 1871, with the atomic mass and properties he had described.
A little scandium makes aluminum alloys stronger for bicycle frames, baseball bats and aircraft parts. Scandium iodide goes into metal-halide lamps that light stadiums and film sets with daylight-like light, and scandium-doped zirconia is used in solid oxide fuel cells.