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Actinium (Ac) – Element 89 of the periodic table

Actinium (symbol Ac) is element number 89 of the periodic table and belongs to the “Actinide” category. Its atomic mass is about 227, and its phase under standard conditions is Solid. This element sits in period 7 and the f-block (Actinides) of the periodic table, and its electrons are arranged in shells of 2, 8, 18, 32, 18, 9, 2. The short electron configuration of Actinium is [Rn] 6d¹ 7s². Known uses of Actinium include Neutron source, Radiation therapy and Scientific research.

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Properties of Actinium

Atomic number
89
Chemical symbol
Ac
Atomic mass
227
Category
Actinide
Period
7
Block
f
Phase
Solid
Protons
89
Electrons
89
Neutrons (approx.)
138
Electron shells
2, 8, 18, 32, 18, 9, 2
Outer-shell electrons
2
Discovered
André-Louis Debierne (1899)

Electron configuration of Actinium

The electron configuration of Actinium (Ac), with 89 electrons, is shown below. The last shell (shell 7) is highlighted:

Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d¹ 7s²
Short configuration
[Rn] 6d¹ 7s²
Last shell
7s²

What is electron configuration and how is it written?

Electron shells of Actinium

Distribution of 89 electrons of Actinium across shells K to Q:

  1. K2
  2. L8
  3. M18
  4. N32
  5. O18
  6. P9
  7. Q2

What is a actinide?

The actinides are the 15 elements from actinium to lawrencium, part of the f-block, and all of them are radioactive.

Uses of Actinium

Frequently asked questions about Actinium

What is the atomic number of Actinium?

The atomic number of Actinium (Ac) is 89; that is, every atom of it has 89 protons.

What is the electron configuration of Actinium?

The electron configuration of Actinium (Ac) is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 6d¹ 7s²; in short form it is [Rn] 6d¹ 7s², and its last shell is 7s².

What is the chemical symbol of Actinium?

The chemical symbol of Actinium is Ac.

Where is Actinium located in the periodic table?

Actinium is located in period 7 and the f-block (Actinides) and belongs to the “Actinide” category.

What is the atomic mass of Actinium?

The atomic mass of Actinium is about 227 (atomic mass units).

What is the phase of Actinium under normal conditions?

The phase of Actinium under standard conditions is Solid.

What are the uses of Actinium?

Uses of Actinium include Neutron source, Radiation therapy and Scientific research.

Who discovered Actinium?

Actinium was discovered by André-Louis Debierne in 1899.

Elements in the same category as Actinium (Actinide)

Thorium (Th)Protactinium (Pa)Uranium (U)Neptunium (Np)Plutonium (Pu)Americium (Am)Curium (Cm)Berkelium (Bk)Californium (Cf)Einsteinium (Es)Fermium (Fm)Mendelevium (Md)Nobelium (No)Lawrencium (Lr)

See all Actinides