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Radium

Element 88 · Alkaline earth metal

Specimen

Atomic number
88
Atomic mass
226.025
State at room temperature
Solid
Melting point
699.9 °C
Boiling point
1,140 °C
Density
5 g/cm³
Discovered
1898

Physical data from PubChem.1

Can I eat it?

In food and water
Radioactive. Food and water contain low levels of radium, and some well water contains more. High exposure causes bone, liver and breast cancer. The US EPA sets a limit for radium in drinking water. 2

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The atom

Ra
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 18
6 (P) 8
7 (Q) outermost 2
Total88

Configuration [Rn] 7s²

7s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 88 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Rn core, with one arrow per electron.

Related elements

Group 2
Be Beryllium Mg Magnesium Ca Calcium Sr Strontium Ba Barium

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Sources

  1. 1

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Atomic mass, electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  2. 2

    Agency for Toxic Substances and Disease Registry (ATSDR), 1990. Radium | ToxFAQs .

    • Everyone is exposed to low levels of radium in the air, water, and food. ... It may be found at higher levels in drinking water from wells.
    • Exposure to high levels of radium results in an increased incidence of bone, liver, and breast cancer.
    • The EPA has set a drinking water limit of 5 picocuries per liter (5 pCi/L) for radium-226 and radium-228 (combined).