For the endothermic reaction CaCO3 (s) ↔ CaO (s) + CO2 (g) Le Châtelier's principle predicts that will result in an increase in the number of moles of CO2.

increasing the temperature

Explanation:

Le Châtelier's principle for an endothermic reaction states that when a stress is added on the system it causes the stress to shift to the direction where the stress can be reduced in other for equilibrium can be achieved.in this case an increase in temperature results in the increase in number of moles of carbon dioxide

it is stable as it is in group 0 which have full outer shells of electrons