Holmium (Ho): Electron Configuration, Properties and Uses
Holmium (Ho): Electron Configuration, Properties and Uses
Electron configuration [Xe] 6s2 4f11 · f-block, lanthanide series · period 6 · Ar 164.93
Holmium data
- Atomic number
- 67
- Relative atomic mass
- 164.93
- Group
- – (lanthanide series)
- Period
- 6
- Block
- f
- Category
- Lanthanide
- Electron configuration
- [Xe] 6s2 4f11
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f11
- Electrons per shell
- 2, 8, 18, 29, 8, 2 (K L M N O P)
- Valence electrons
- 2 (in the outer shell)
- Electronegativity (Pauling)
- 1.23
- First ionisation energy
- 6.022 eV
- Atomic radius (van der Waals)
- 216 pm
- State at room temperature
- Solid
- Melting point
- 1474 °C
- Boiling point
- 2700 °C
- Density
- 8.8 g/cm³
- Common oxidation states
- +3
- Discovered
- 1878
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 29 · O 8 · P 2
Orbital diagram (outer electrons)
About holmium
With atomic number 67, holmium (Ho) has 67 protons in its nucleus and 67 electrons as a neutral atom. It belongs to the lanthanide series in period 6 (f-block), usually shown below the main table. The element was discovered in 1878. Holmium is a solid at room temperature, melting at 1474 °C and boiling at 2700 °C.
Holmium electron configuration
The electron configuration of holmium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f11, or in short [Xe] 6s2 4f11. Its electrons occupy 6 shells: K = 2, L = 8, M = 18, N = 29, O = 8, P = 2. As a lanthanide, holmium fills the 4f subshell. Its outer 6s subshell holds 2 electrons; valence electrons for this series are not assigned by the usual group rule. When it forms cations, electrons leave the outermost subshell first: Ho3+ = [Xe] 4f10.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p6(54) → 6s2(56) → 4f11(67)
Uses of holmium
In industry and the laboratory, holmium turns up in many places, for example holmium lasers for medical procedures such as breaking kidney stones, and pole pieces for high-field magnets.
Safety
Bulk holmium has low toxicity. The main hazards are its dust and salts, so always check the SDS of the compound you use. Always read the safety data sheet (SDS) before working with a chemical.
Other lanthanides
Frequently asked questions
What is the electron configuration of holmium?
The electron configuration of holmium (Ho, atomic number 67) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f11, or [Xe] 6s2 4f11 in short. By shell: 2, 8, 18, 29, 8, 2.
How many valence electrons does holmium have?
Holmium has 2 electrons in its outer shell. For lanthanides and actinides, valence electrons are not assigned by the usual group rule.
Which group and period is holmium in?
Holmium is in the lanthanide series, period 6, f-block.
What is the atomic mass of holmium?
The relative atomic mass of holmium is 164.93. Use it to calculate molar mass with the molar mass calculator.
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