The following reaction is exothermic
Which change would shift the equilibrium over to the left
2SO2(g)+O2(g)=2SO3(g)

Increase in temperature

Explanation:

Once there is an increase in temperature of the exothermic reaction, the equilibrium position shifts to the left since equilibrium constant, K decreases; hence favoring the formation of reactants which are 2SO2(g) and O2(g).

Decrease in temperature, on the other hand, would shift the equilibrium to the right since equilibrium constant, K increases.

Thus, for the exothermic reaction 2SO2(g)+O2(g)=2SO3(g): increase in temperature would shift the equilibrium over to the left.

neutrons are in the middle of the atom and the electrons, which are much smaller.