35Bromine

Bromine is a halogen in group 17, period 4. At 25 °C it is a liquid.

Shells: 2, 8, 18, 7. A simple picture: electrons do not move in circles.

Symbol: Br
Atomic number: 35 protons in the nucleus
Standard atomic weight: 79.904 ± 0.003
Electron configuration: [Ar] 3d¹⁰ 4s² 4p⁵
Electrons in each shell: 2, 8, 18, 7
Group, period, block: 17, 4, p
Family: Halogens
State at 25 °C: liquid
Electronegativity: 2.96 (Pauling scale)
First ionisation energy: 1139.9 kJ/mol (11.81381 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.