89 - Actinium actinide
Discovered by Friedrich Oskar Giesel in 1899
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.
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
57-71 La-Lu Lanthanides
89-103 Ac-Lr Actinides
| 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 |
227 u Atomic Mass
3.47k K Boiling Point
3 Group
3 Common Oxidation States
2.15 Å Covalent Radius
10 g/cm³ Density
33.8 kJ/mol Electron Affinity
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 6d1 Electron Configuration
[Rn] 6d1 7s2 Electron Configuration (semantic)
1.1 Electronegativity
89 Electrons
5.17 eV First Ionization Energy
499, 1170 kJ/mol Ionization Energies
1.32k K Melting Point
48 Mendeleev Number
27.2 J/(mol·K) Molar Heat
7 Number of Shells
138 Neutrons
89 Atomic Number
11 Number of Isotopes
3 Oxidation States
7 Period
Solid Phase
89 Protons
2, 8, 18, 32, 18, 9, 2 Electron Shell Occupations
0.12 J/(g K) Specific Heat