Periodic table / Alkaline earth metals

88Radium

Radium is an alkaline earth metal in group 2, period 7. At 25 °C it is a solid.

Shells: 2, 8, 18, 32, 18, 8, 2. A simple picture: electrons do not move in circles.

Symbol: Ra
Atomic number: 88 protons in the nucleus
Standard atomic weight: None. Radium has no stable isotopes, so the mass of a sample depends on which isotopes it holds.
Electron configuration: [Rn] 7s²
Electrons in each shell: 2, 8, 18, 32, 18, 8, 2
Group, period, block: 2, 7, s
Family: Alkaline earth metals
State at 25 °C: solid
Electronegativity: 0.9 (Pauling scale)
First ionisation energy: 509.3 kJ/mol (5.2784239 eV)

Where these numbers come from

Atomic weight: IUPAC CIAAW, abridged standard atomic weights 2024. Electron configuration and ionisation energy: NIST Atomic Spectra Database. Family, state and electronegativity: PubChem. See Sources. Melting points, boiling points and densities are left out for now: published values differ between sources, and we will add them once each has been checked.