What patterns are observed in the stated properties as Group $2$ is descended from magnesium to barium?
- Adecomposition temperature of the carbonate decreases; first ionisation energy increases
- Bdecomposition temperature of the carbonate decreases; first ionisation energy decreases
- Cdecomposition temperature of the carbonate increases; first ionisation energy increases
- Ddecomposition temperature of the carbonate increases; first ionisation energy decreases