All practice pages/Interatomic theory/Elements
Element 87, an alkali metal
The last element discovered in nature, so short-lived that only about an ounce of it exists on Earth at any moment.
Period 7, group 1. The other alkali metals are tinted, and every cell opens its own article.
Francium has 87 electrons, one for every proton, so the atom carries no charge. Below are the same 87 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s¹
Short form: [Rn] 7s¹, where [Rn] stands for the 86 electrons radon already has.
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.
Francium sits in period 7 and has 7 shells. The period number counts the shells.
The outer shell holds 1 electron. Those are the ones francium can lose, gain or share, so they are the ones that decide what it bonds with. For a main-group element the group number gives that count: group 1 means 1.
One valence electron, which francium gives up easily to form the Fr⁺ ion. Like the other alkali metals, it reacts with water.
Formed in tiny amounts in uranium and thorium ores as actinium decays. Only about 20 to 30 grams are thought to exist in Earth's crust at any moment.
Marguerite Perey, a former assistant of Marie Curie, found it in 1939 at the Curie Institute in Paris while purifying actinium, and named it after France. In 1962 she became the first woman elected to the French Academy of Sciences, as a corresponding member.
None outside research. Physicists trap clouds of a few hundred thousand francium atoms with lasers to test theories of atomic structure.
Intensely radioactive; it is only ever handled a few atoms at a time.