Holmium is a silvery lanthanide used in some magnetic alloys and in neutron-absorbing applications. It occurs as a minor constituent of rare-earth minerals and can be recovered during yttrium processing. Its story connects specialized material behavior to the challenge of separating chemically similar elements.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
How can holmium oxide glass reveal an error in a spectrophotometer’s wavelength scale?
Holmium oxide reference glass
FOLLOW THIS RELATIONSHIP
Use characterized absorption features
Holmium oxide reference glass has characterized absorption features. Their reference wavelengths provide comparison points for an instrument’s assignment of spectral positions.
Explore the model (optional)
HoFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
Agreement with the glass reference most directly checks which instrument property?
Atomic identity, reference properties and structure models
INTERACTIVE 3D67 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Xe] 4f11 6s2. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Marc Delafontaine and Louis Soret observed evidence for holmium in 1878 while examining rare-earth ; subsequent separation work helped distinguish the new constituent. Early preparations were not necessarily pure. In 1961, the US National Bureau of Standards began distributing holmium glass as wavelength-reference material. That makes an elegant historical connection: characteristic first helped distinguish an element and later helped test whether instruments measured correctly.
1878
Spectral evidence observed
Delafontaine and Soret recognized unexplained rare-earth spectral lines.
1961
Reference glass distributed
NBS began distributing holmium oxide glass wavelength standards.
Holmium occurs in small amounts within rare-earth and is recovered through separation of mixed rare-earth material. It is not normally a native-metal resource. Its path from mineral to optical standard passes through chemical purification and controlled glass preparation, each of which contributes to the reliability of the final product.
Holmium-containing materials exhibit characteristic optical absorption useful for measurement. Their magnetic and neutron-interaction properties support other specialized applications. These behaviors must be tied to the relevant form and conditions. A reference glass provides reproducible absorption features; it does not display every possible spectral line of an isolated holmium atom.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
1734 K
at standard pressure unless noted
Boiling point in K
2993 K
101.325 kPa
Density in g/cm³
8.79 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
1.23 Pauling
Pauling scale
First ionization energy in kJ/mol
581 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
192 pm
single-bond covalent radius
Common oxidation states
+3
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
1.3 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1878 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 6
Ho 1.23 Pauling · Holmium
Electronegativity across period 6. Exact values.
Cs
0.79
Ba
0.89
La
1.1
Ce
1.12
Pr
1.13
Nd
1.14
Sm
1.17
Eu
1.2
Gd
1.2
Tb
1.1
Dy
1.22
Ho
1.23
Er
1.24
Tm
1.25
Yb
1.1
Lu
1.27
Hf
1.3
Ta
1.5
W
2.36
Re
1.9
Os
2.2
Ir
2.2
Pt
2.28
Au
2.54
Hg
2
Tl
1.62
Pb
2.33
Bi
2.02
Po
2
At
2.2
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
