Input interpretation
period 1 elements | atomic radius
Results
hydrogen | 25 pm (picometers) helium | 31 pm (picometers)
period 1 elements | atomic radius | 28 pm (picometers) (median)
Relative values
| visual | ratios | | comparisons hydrogen | | 0.8 | 1 | 19% smaller helium | | 1 | 1.2 | 24% larger
Plot
Plot
Periodic table location
Periodic table location
Atomic radii properties
| hydrogen | helium atomic radius (empirical) | 25 pm | atomic radius (calculated) | 53 pm | 31 pm covalent radius | 31 pm | 28 pm van der Waals radius | 120 pm | 140 pm
Units
Unit conversions for median atomic radius 28 pm
0.028 nm (nanometers)
2.8×10^-11 meters
1.1×10^-9 inches
0.28 Å (ångströms)
Comparisons for median atomic radius 28 pm
≈ 0.9 × atomic radius of helium (the smallest atom) ( ≈ 31 pm )
≈ 1.1 × atomic radius of hydrogen ( ≈ 25 pm )