Lanthanides (Lanthanide Series)
Lanthanum to lutetium, elements 57 to 71: the first row of the f-block, where the 4f subshell fills.
What they have in common
The lanthanides fill the 4f orbitals, which lie deep inside the atom. Because those electrons barely reach the outside, the fifteen elements behave very similarly: most form 3+ ions and they occur together in the same ores, which made them hard to separate.
Their radii shrink steadily across the series (the lanthanide contraction) because 4f electrons shield poorly. As a result, hafnium ends up nearly the same size as zirconium above it. With scandium and yttrium they make up the rare earth elements used in NdFeB magnets, phosphors and lasers.
- Mostly +3 ions
- Silvery reactive metals
- Lanthanide contraction across the series
- Strong magnetic and luminescent properties
Lanthanides at a glance
| Element | Z | Mass | Configuration | Valence e⁻ | Charges | EN | Radius (pm) |
|---|---|---|---|---|---|---|---|
| Lanthanum (La) | 57 | 138.905 | [Xe] 5d1 6s2 | 3 | 3+ | 1.1 | 169 |
| Cerium (Ce) | 58 | 140.116 | [Xe] 4f1 5d1 6s2 | 3 | 3+, 4+ | 1.12 | — |
| Praseodymium (Pr) | 59 | 140.908 | [Xe] 4f3 6s2 | 2 | 3+ | 1.13 | — |
| Neodymium (Nd) | 60 | 144.242 | [Xe] 4f4 6s2 | 2 | 3+ | 1.14 | — |
| Promethium (Pm) | 61 | [145] | [Xe] 4f5 6s2 | 2 | 3+ | 1.13 | — |
| Samarium (Sm) | 62 | 150.36 | [Xe] 4f6 6s2 | 2 | 3+, 2+ | 1.17 | — |
| Europium (Eu) | 63 | 151.964 | [Xe] 4f7 6s2 | 2 | 3+, 2+ | 1.2 | — |
| Gadolinium (Gd) | 64 | 157.25 | [Xe] 4f7 5d1 6s2 | 3 | 3+ | 1.2 | — |
| Terbium (Tb) | 65 | 158.925 | [Xe] 4f9 6s2 | 2 | 3+ | 1.2 | — |
| Dysprosium (Dy) | 66 | 162.5 | [Xe] 4f10 6s2 | 2 | 3+ | 1.22 | — |
| Holmium (Ho) | 67 | 164.93 | [Xe] 4f11 6s2 | 2 | 3+ | 1.23 | — |
| Erbium (Er) | 68 | 167.259 | [Xe] 4f12 6s2 | 2 | 3+ | 1.24 | — |
| Thulium (Tm) | 69 | 168.934 | [Xe] 4f13 6s2 | 2 | 3+ | 1.25 | — |
| Ytterbium (Yb) | 70 | 173.054 | [Xe] 4f14 6s2 | 2 | 3+, 2+ | 1.1 | — |
| Lutetium (Lu) | 71 | 174.967 | [Xe] 4f14 5d1 6s2 | 3 | 3+ | 1.27 | 160 |
Questions students ask
Why are lanthanides placed below the table?
They belong in period 6 between barium and hafnium, but printing them inline would make the table 32 columns wide.
Are lanthanides rare?
Not especially. Cerium is about as abundant in the Earth’s crust as copper. They are “rare” because they rarely form concentrated ores and are hard to separate.