Radium (Ra)

Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen on exposure to air.

Atomic Number

88

Atomic Mass

226 u

Category

alkaline earth

Phase

solid

Density

5.5 g/cm³

Electron Shells

2, 8, 18, 32, 18, 8, 2

Atomic Structure

Protons: 88 • Electrons: 88 • Neutrons: Varies by isotope

Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s²

Discovery

1898 • Marie Curie, Pierre Curie