Gadolinium

Gadolinium (Gd) is a lanthanide with atomic number 64 and an atomic mass of 157.25. Its electron configuration is [Xe] 4f7 5d1 6s2.

Gadolinium key data

Symbol	Gd
Atomic number	64
Atomic mass (standard atomic weight)	157.25
Molar mass	157.25 g/mol
Protons	64
Neutrons (most abundant isotope, gadolinium-158)	94
Electrons (neutral atom)	64
Category	Lanthanide
Period	6
Group	f-block, no group
Block	f-block
Noble gas notation	[Xe] 4f7 5d1 6s2
Full electron configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f7 5s2 5p6 5d1 6s2
Electrons per shell	2, 8, 18, 25, 9, 2

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

Measured properties of gadolinium

From PubChem, the US National Institutes of Health. Public domain. PubChem’s periodic table gives no value for the rows not shown.

Melting point	1586 K (1312.9 °C), 37th of 103 by melting point
Boiling point	3546 K (3272.9 °C), 26th of 93 by boiling point
Density	7.9 g/cm³, 40th of 96 by density
State at room temperature	Solid
Electronegativity	1.2 (Pauling), 79th of 95 by electronegativity
Van der Waals radius	237 pm, joint 20th of 99 by atomic radius
First ionisation energy	6.15 eV (593 kJ/mol), 71st of 102 by first ionisation energy
Common oxidation states	+3
Discovered	1880

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Gadolinium electron configuration

The full electron configuration of gadolinium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f7 5s2 5p6 5d1 6s2. With the noble-gas core collapsed it is [Xe] 4f7 5d1 6s2, and the outermost subshell is 6s2.

Gadolinium does not follow the simple filling order. Its measured configuration differs from the one the aufbau rule predicts, because a half-filled 4f subshell sits lower in energy, so the electron that would be its eighth goes into 5d instead. This is a measured fact about the atom rather than an exception to be derived.

Bohr model of gadolinium (Gd): a nucleus and six shells holding 2, 8, 18, 25, 9 and 2 electrons from the inside out. — Bohr model of gadolinium (Gd). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Orbital box diagram of gadolinium (Gd), [Xe] 4f7 5d1 6s2, with the xenon core drawn as one bar: one box per orbital, filled by Hund’s rule, showing eight unpaired electrons, in 4f and 5d. — Orbital diagram of gadolinium (Gd). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one gadolinium atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

one atom = 157.25 / (6.02214076 × 10²³)
= 2.6112 × 10⁻²² g

Atoms in one gram

atoms per gram = 6.02214076 × 10²³ / 157.25
= 3.8297 × 10²¹ atoms

Gadolinium on the periodic table

Gadolinium is in period 6, outside the numbered groups, in the f-block.