Which element can achieve the same electron configuration as a noble gas when the atom forms an ion?

Question

argon
iron
nickel
potassium

Answer 1

s-block and p-block elements can all do this. You did not give a choice for us to use so I will tell all of this:
group 1A will form 1+ ions to = noble gas
group 2A will form 2+ ions to = noble gas
group 3A will form 3+ ions to = noble gas
group 4A will form either 4+ or 4- ions to = noble gas
group 5A will form 3- ions to = noble gas
group 6A will form 2- ions to = noble gas
group 7A will from 1- ions to = noble gas
group 8A will not form ions since they already are the noble gases.

Answer 2

Calcium is 2 elements higher than the nearest noble gas. So, to have the noble gas configuration, it would have to lose 2 electrons. Bromine is 1 lower than the nearest noble gas, so Br^- has the 1 extra electron needed to have the same number of electrons as the noble gas. Group VA would have to gain 3 electrons, because it's 3 lower than the noble gasses.