16

8

4

2

$Na$

$K$

$Pt$

$Fe$

$Mg$

$Hg$

$Fe$

$Zn$

Helium

Bismuth

Antimony

Sodium

$_1{{\rm{H}}^1}$

$_1{{\rm{H}}^2}$

$_1{{\rm{H}}^3}$

All the same reactivity

Is heated to a very high temperature

Is subjected to extremely high pressure

Is reacted with a strong acid

Is combined with a metal

${\rm{B}}{{\rm{r}}_2}$

$Ca$

${{\rm{N}}_2}$

$S$

Protium

Deuterium

Tritium

All isotopes of hydrogen contain neutrons

${{\rm{H}}_2}{\rm{S}}$

${{\rm{H}}_2}{\rm{O}}$

${{\rm{H}}_2}{\rm{Se}}$

${{\rm{H}}_2}{\rm{Te}}$

Electrolysis of pure water

Electrolysis of warm aqueous Barium hydroxide

Action of $Zn$ on $NaOH$

Electrolysis of acidulated water

Hydrogen is liberated at the cathode

Hydrogen is liberated at the anode

Hydride ion migrates towards cathode

No reaction takes place