1. they vary with a higher number because boiling is way hotter than melting
the answer is 6 valence electrons.
valence is the # of electrons on the outer most shell of an atom.
oxygen has 6.
although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.
if you need further assistance, let me know: )