Eli5: Why does Helium have a lower melting point than Hydrogen?

Question

Pure hydrogen is less dense than pure helium. Why does it have a higher melting point?

In: Chemistry

Answer 1

The phases of a material (solid liquid gas) don’t just depend on density, but also on the forces or links between the atoms (i.e. on the orbitals / chemistry of the atoms).

So helium atoms generally don’t react with other helium atoms, whereas hydrogen atoms usually form covalent bonds (form hydrogen molecules, H2). So these bonds require extra energy to “break apart” and get a material from, say, solid to liquid, or from liquid to gas.