Help!!! giving if correct and both explained

What is the formula that this ionic compounds could form sr2+p3-o2-

Agas is contained in a thick walled balloon when the pressure changes from 1.21 atm to 2.52 the volume changes from 3.75 l to 1.72 l and the temperature change from 293k to blank k

Achange in the number of neutrons in an atom will change an blank . when the number of protons changes in an atom, a new element will form.