helium

| Introduction | History | Other Periodic Tables | Back |

Symbol:

He

Atomic Number:

2

Relative Atomic Mass:

4.002602 g mol^-1

Natural Abundance in Lithosphere, hydrosphere and atmosphere:

4 x 10^-7% (mass fraction)

Electron Configuration:

1s²

Van der Waals Radius:

140pm

Boiling Point:

-268.9°C

Density:

0.17 g L^-1 (at 1013 mbar)

First Ionisation Energy:

24.587 eV

Number of Natural Isotopes:

2

Mass Number of the Most Abundant Isotopes:

3 g mol^-1 a 10^-4% abundance

4 g mol^-1 a ~100% abundance