He
Helium
Z 2 4.003 g/molNoble Gas
Nucleus
2 Protons
2 Neutrons
2 Electrons (2 Valence)
Shell distribution: K2 • L0 • M0 • N0 • O0 • P0 • Q0
Electron Configuration
Energy
7p
6d
5f
7s
6p
5d
4f
6s
5p
4d
5s
4p
3d
4s
3p
3s
2p
2s
1s
1s2
Oxidation States
CommonRare
0
Radii
Empirical
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Calculated
31 pm0.31 Å
Covalent
28 pm0.28 Å
Van der Waals
140 pm1.4 Å
Ionic
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Crystal Structure
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Hexagonal close-packed
Pearson symbol
hP2
Space group
P63/mmc No. 194