What occurs when a gas is changed into a liquid

for liquid to gas, Evaporation or vaporization.

for gas to liquid, condensation occurs. The opposite of evaporation. Condensation is when the gas gives up it's latent heat and simply condenses.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8