« back

89 - Actinium actinide

Discovered by Friedrich Oskar Giesel in 1899

Actinium

Actinium is a radioactive chemical element with symbol Ac (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902.
Shell Electrons Orbitals
1 2 2 in 1s
2 8 2 in 2s + 6 in 2p
3 18 2 in 3s + 6 in 3p + 10 in 3d
4 32 2 in 4s + 6 in 4p + 10 in 4d + 14 in 4f
5 18 2 in 5s + 6 in 5p + 10 in 5d
6 9 2 in 6s + 6 in 6p + 1 in 6d
7 2 2 in 7s
ActiniumAc Electron 1 Electron 2 Electron 1 Electron 2 Electron 3 Electron 4 Electron 5 Electron 6 Electron 7 Electron 8 Electron 1 Electron 2 Electron 3 Electron 4 Electron 5 Electron 6 Electron 7 Electron 8 Electron 9 Electron 10 Electron 11 Electron 12 Electron 13 Electron 14 Electron 15 Electron 16 Electron 17 Electron 18 Electron 1 Electron 2 Electron 3 Electron 4 Electron 5 Electron 6 Electron 7 Electron 8 Electron 9 Electron 10 Electron 11 Electron 12 Electron 13 Electron 14 Electron 15 Electron 16 Electron 17 Electron 18 Electron 19 Electron 20 Electron 21 Electron 22 Electron 23 Electron 24 Electron 25 Electron 26 Electron 27 Electron 28 Electron 29 Electron 30 Electron 31 Electron 32 Electron 1 Electron 2 Electron 3 Electron 4 Electron 5 Electron 6 Electron 7 Electron 8 Electron 9 Electron 10 Electron 11 Electron 12 Electron 13 Electron 14 Electron 15 Electron 16 Electron 17 Electron 18 Electron 1 Electron 2 Electron 3 Electron 4 Electron 5 Electron 6 Electron 7 Electron 8 Electron 9 Electron 1 Electron 2
227  u Atomic Mass
3471  K Boiling Point
2.15  Å Covalent Radius
10  g/cm³ Density
33.77 Electron Affinity
1.1 Electronegativity
5.17  eV First Ionization Energy
1323.15  K Melting Point
7 Number of Shells
89 Atomic Number
2, 8, 18, 32, 18, 9, 2 Electron Shell Occupations
0.12  J/(g K) Specific Heat