←H   H↑   ↓F   He→

Wasserstoff ∙ hydrogène ∙ idrogeno ∙ hidrógeno
group ‘h+h’ / hydrogen and halogens: RH

• melting point: -255.34°C
• boiling point: -252.87°C
• density: 0.084 g/l

The most common primary cosmic ray particle is the ubiquitous proton or hydrogen nucleus. — cosmic.lbl.gov

⚒ minerals:
Ice

Tritium […] is a vital and perishable ingredient of nuclear bombs. Inside a hydrogen bomb […] a fission bomb explosion ignites a tritium-deuterium fusion reaction. — NYT

☢ radioisotopes:
H-3 (T1/2=12.3 a) cosmogenic, activation product

Tritium (³H) also occurs naturally – background level being ca. 1 Bq/l rainwater. Nuclear age peak tritium rainwater concentration was up to 500 Bq/l in 1963.