The protons are equivalent to the atomic number, so we can determine that the element being expressed here is Magnesium. If you are ever stuck on what element you are finding your information from, just remember that the number of protons is the exact same as the atomic number in ANY situation :)
The charge of magensium is +2, with an atomic mass of 24. So A would be your answer :)
Greater than (less space = less room for the particles to bounce around in = bounce around faster (hits walls/each other more often) = greater pressure)
8A+2B——> 6C
since you multiply by a factor of 2 you do that to each letter
4*2=8
1*2=2
3*2=6
