That would be Protons and Neutrons.
Increasing the pressure on a reaction involving reacting gases increases the rate of reaction. Changing the pressure on a reaction which involves only solids or liquids has no effect on the rate.
The first ionization energy is the energy that the atom lost its first electrons. The energy decrease and the atom is more reactive. So from highest to lowest is Li>Na>K>Rb.
MAGNESIUM(Mg) posses the up mentioned electronic configuration