Help with number two please! And If possible please explain why

If it is an isoelectronic series select true, if not select false. o2-, s2-, se2-, te2- na+, k+, rb+, cs+ n3-, p3-, as3-, sb3- ag, cd+, sn3+, sb4+ f-, cl-, br-, i- f-, ne, na+, mg2+ s2-, s, s6+

If the solubility of a gas in water is 1.22 g/l at 2.75 atm, what is its solubility (in g/l) at 1.0 atm?

Why protons do not repal in the nucleus