What does sodium form an ion a+1 charge

It has only 1 electron in its valence shell and if that electron is removed it will acquire noble gas configuration

Explanation:

Sodium forms an ion of charge +1 as in its ionic state it has inert gas configuration

It forms an ion of charge +1 when the valence shell electron is removed to gain the noble gas configuration and the electrons can be removed mostly from its valence shell because inner shell electrons will be tightly bounded to the nucleus of the atom and it requires high energy to remove the electron present in the inner shell when compared to the valence shell (outermost shell)

d. air pressure decreases as altitude increases.