Answer:
Magnesium (Mg)
Step-by-step explanation:
An element with a lower atomic mass than Calcium that has similar chemical property is the element Magnesium (Mg).
This because, elements in the same group or family on the periodic table has similar chemical properties.
Magnesium belongs to the same group as Calcium, other elements are:
Be Mg Ca Sr Ba Ra
The group is made of the alkaline earth metals. They have two valence electrons in their outer shell.