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Periodic table / Metalloids

33Arsenic

Arsenic is a metalloid in group 15, period 4. At 25 °C it is a solid.

As
Shells: 2, 8, 18, 5. A simple picture: electrons do not move in circles.
Symbol
As
Atomic number
33 protons in the nucleus
Standard atomic weight
74.922 ± 0.001
Electron configuration
[Ar] 3d10 4s2 4p3
Electrons in each shell
2, 8, 18, 5
Group, period, block
15, 4, p
Family
Metalloids
State at 25 °C
solid
Electronegativity
2.18 (Pauling scale)
First ionisation energy
944.5 kJ/mol (9.78855 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.