Periodic Table
1
H
1.008
Hydrogen
NonmetalLightest element; behaves like both Group 1 and Group 17.
Electronic Configuration
1s¹or1s¹
Electron shells
1e⁻n=1
Properties
Atomic number
1
Atomic mass
1.008 u
Category
Nonmetal
Block / Group / Period
s · 1 · 1
Valence electrons
1
Oxidation states
+1, -1
Electronegativity
2.2
Atomic radius
53 pm
Ionization energy
1312 kJ/mol
Electron affinity
73 kJ/mol
Melting point
14 K / -259 °C
Boiling point
20 K / -253 °C
Density
0.00009 g/cm³
State at 25 °C
gas
JEE / NEET notes
- Placed in Group 1 but resembles Group 17 (1 electron short of He).
- Forms H⁻ (hydride) with active metals — strong reducing agent.
- Ortho & para hydrogen differ in nuclear spin.
Exceptions
- • Has no neutrons in its common isotope (protium).
Uses
Haber process (NH₃) · Hydrogenation of oils · Rocket fuel · Fuel cells
Important compounds
H₂OH₂O₂NH₃HCl
Did you know? Most abundant element in the universe (~75% by mass).
Personal Notes
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