Answer:
Sr has highest boiling point at standard pressure
Explanation:
Comparison of boiling points for these given elements require two factors namely- (1) atomic mass and (2) valency
Higher the atomic mass of an element, higher will be its boiling point. Because, with increase in atomic mass, van der waal forces between atoms increase. So more energy is required to boil an element by disrupting this interatomic force.
Higher the valency of an element, higher will be its boiling point. This is due to increase in bonding energy.
Here, Sr has higest atomic mass as well as it is bivalent. So Sr has highest boiling point.
