All practice pages/Interatomic theory/Elements
Element 100, an actinide
Found in the same hydrogen bomb debris as einsteinium, and named for Enrico Fermi, who built the first nuclear reactor.
Period 7, in the actinide row set below the main table. The other actinides are tinted, and every cell opens its own article.
Fermium has 100 electrons, one for every proton, so the atom carries no charge. Below are the same 100 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹² 6s² 6p⁶ 7s²
Short form: [Rn] 5f¹² 7s², where [Rn] stands for the 86 electrons radon already has.
That list runs by shell. In the order the subshells fill it reads [Rn] 7s² 5f¹², 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 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.
Fermium sits in period 7 and has 7 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones fermium can lose, gain or share, so they are the ones that decide what it bonds with.
Radioactive, like every actinide. It gives up electrons to form positive ions.
Not found in nature; made in trace amounts in high-flux reactors.
Albert Ghiorso's team found it in 1952 in debris from the Ivy Mike hydrogen bomb test, alongside einsteinium, and it was named in 1955 after Enrico Fermi. It is the heaviest element that can be made by bombarding lighter elements with neutrons; everything heavier needs a particle accelerator.
Research only.
Radioactive; only trace amounts have ever been made.