symbols theoretical descriptions

If the charge is +3 this means the nucleus has three more protons than electrons. If there are 18 electrons, the number of protons is 18 + 3 = 21. The element with 21 protons is Scandium.

No atom can have 33 protons and only 3 electrons. This would give it a charge of +30 and this is impossible. The element with 33 protons is Arsenic. Arsenic can have a charge of -3 or +3.

Element with two protons is surely helium. Helium is a noble gas which means it is not very reactive. Also as you move across the periodic table of elements from left to right, left is the most reactive and right is the least reactive therefore since helium is on the farthest right side it is not very reactive. Another thing is when you move down a column the reactivity increases, and since helium is at the top of the periodic table, it is very unreactive. All these factors show that Helium is the least reactive element there is on the periodic table, and it is doubtful that will change because the table is pretty much in the state it will be in as we discover new elements because those new ones will end up in the blanks on the table.

We know from the periodic table that Arsenic has 33 protons. 3 extra electrons makes it negative.