When heated, a mixture of hydrogen and neon gases emits light and burns in a flame.When heated, the atoms in the gas absorb energy, causing the electrons to jump to higher energy levels. When the electrons return to their original energy levels, they emit light.

A mixture of helium and nitrogen does not burn in a flame because both helium and nitrogen are non-flammable.

A mixture of helium and neon does not burn in a flame because helium and neon are non-reactive.

A mixture of neon and nitrogen will not burn in a flame because neither neon nor nitrogen are flammable.