#1 Hydrogen

Hydrogen is a chemical element with symbol H and atomic number 1. With a standard atomic weight of1.008, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.

Atomic Weight : 1.008

Melting Point : -259.14 C

Boiling Point : -252.87 C

Density : 0.0899 g/l[note]