Periodic Table
57
La
138.91
Lanthanum
LanthanoidHead of lanthanoids; 5d¹ (no 4f); used in alloys & optics.
Electronic Configuration
[Xe] 5d¹ 6s²or1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 5d¹ 6s²
Electron shells
2e⁻n=1
8e⁻n=2
18e⁻n=3
18e⁻n=4
9e⁻n=5
2e⁻n=6
Properties
Atomic number
57
Atomic mass
138.91 u
Category
Lanthanoid
Block / Group / Period
d · 3 · 6
Valence electrons
2
Oxidation states
+3
Electronegativity
1.1
Atomic radius
195 pm
Ionization energy
538 kJ/mol
Electron affinity
48 kJ/mol
Melting point
1193 K / 920 °C
Boiling point
3737 K / 3464 °C
Density
6.145 g/cm³
State at 25 °C
solid
Personal Notes
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