All practice pages/Interatomic theory/Elements
Element 88, an alkaline earth metal
The glowing element that made the Curies famous, painted onto watch dials until the painters began to fall ill.
Period 7, group 2. The other alkaline earth metals are tinted, and every cell opens its own article.
Radium has 88 electrons, one for every proton, so the atom carries no charge. Below are the same 88 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s²
Short form: [Rn] 7s², 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.
Radium sits in period 7 and has 7 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones radium 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 2 means 2.
Two valence electrons, which radium gives up to form the Ra²⁺ ion in its compounds.
Present in uranium ores at about one part in three million of the uranium, as one step in uranium's decay.
Marie and Pierre Curie, working with Gustave Bémont, announced it in December 1898. It took Marie Curie years of processing tons of pitchblende waste to isolate a tenth of a gram of radium chloride in 1902, and she and André-Louis Debierne isolated the metal in 1910. The name comes from the Latin radius, ray.
In the early 1900s radium went into glow-in-the-dark paint for watches and instruments, and into quack tonics and cosmetics. Dial painters who shaped their brushes with their lips, the Radium Girls, developed bone cancers, and their lawsuits changed workplace safety law. Today radium-223 treats prostate cancer that has spread to the bones.
Radioactive, and stored by the body in bone as if it were calcium, where it causes cancer. The curie, a unit of radioactivity, was originally based on one gram of radium-226.