Magnesium (Mg)

Magnesium is a chemical element with symbol Mg and atomic number 12. It is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column of the periodic table.

Atomic Number

12

Atomic Mass

24.305 u

Category

alkaline earth

Phase

solid

Density

1.738 g/cm³

Electron Shells

2, 8, 2

Atomic Structure

Protons: 12 • Electrons: 12 • Neutrons: Varies by isotope

Electron Configuration: 1s² 2s² 2p⁶ 3s²

Discovery

1755 • Joseph Black