Er
Erbium
Z 68 167.259 g/molLanthanide
Nucleus
68 Protons
99 Neutrons
68 Electrons (3 Valence)
Shell distribution: K2 • L8 • M18 • N30 • O8 • P2 • Q0
Electron Configuration
Energy
7p
6d
5f
7s
6p
5d
4f
6s
5p
4d
5s
4p
3d
4s
3p
3s
2p
2s
1s
[Xe]4f126s2
Oxidation States
CommonRare
0
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Radii
Empirical
175 pm1.75 Å
Calculated
226 pm2.26 Å
Covalent
189±6 pm1.89±0.06 Å
Van der Waals
235 pm2.35 Å
IonicEr3+
89 pm0.89 Å
Crystal Structure
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Hexagonal close-packed
Pearson symbol
hP2
Space group
P63/mmc No. 194