If an atom has 1 valance electron, will it gain or lose electrons when it bonds? how many? why? what about with 7?

No it won't lose but it will gain and it gain up to it will fill 8 and because it need to satisfy the octet rule 7 will lose or gain electron and because it needs to stastify the octet rule by filling it up till 8 valence electron

If valence electron is 1, atom will gain 1 electron(in case of hydrogen) to complete its duplet to obtain stability. Atoms gain, lose or share electrons to gain stability. Every element tries to attain its nearest noble element. Example : He is the noble gas element with 2 valence electrons(stable in nature) whereas H(non-metal) has only 1 valence electron so it'll form electron bond with that element which requires 1 electron to complete its octet or duplet(2 valence electrons, ex: He). Whereas in case of metals with 1 valence electron(example : Na), it'll lose to gain the nearest stable octet i.e Ne. Metals lose electrons because electrons are loosely bounded in them whereas non-metals gain electrons gain electrons. Halogen group have 7 valence electrons hence they'll accept 1 electron to complete their octet and attain stable nature. Hope this helps!

The answer is c. 320 g

Density and pressure