Actinium (Ac)
Actinium
Actinium (Ac) is an actinide in period 7. Its relative atomic mass is [227] and the molar mass of the atom is [227] g/mol.
Atomic number 89
Atomic mass [227] predicted
Molar mass [227] g/mol
Category Actinide Solid
Properties of actinium
| Atomic number | 89 |
|---|---|
| Symbol | Ac |
| Latin name | Actinium |
| Relative atomic mass | [227] |
| Molar mass | [227] g/mol |
| Group, period, block | —, 7, f |
| Category | Actinide |
| State at 20 °C | Solid |
| Electron configuration | [Rn] 6d¹ 7s² |
| Electronegativity (Pauling) | 1.1 |
| Atomic radius | 195 pm |
Electron configuration of actinium
Electrons per shell
K2L8M18N32O18P9Q2
Full notation
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d¹ 7s²
Noble-gas notation
89 protons · 89 electrons[Rn] 6d¹ 7s²
Formula and compounds of actinium
Simple substanceAcactiniumMolar mass of Ac: [227] g/mol
Chemistry not clicking? Try a lesson with a tutor
1-to-1 online chemistry lessons for KS3, GCSE and A-level. Your first lesson is a free trial.
Frequently asked questions
The relative atomic mass of actinium is [227], so the molar mass of the atom is [227] g/mol.
Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d¹ 7s². Noble-gas notation: [Rn] 6d¹ 7s².