Answer: Be, Ca, Ra
Explanation:
Elements are distributed in groups and periods in a periodic table.
Elements that belong to same groups will show similar chemical properties because they have same number of valence electrons.
Berrylium (Be) , Calcium (Ca) and radon (Rn) are elements which belong to Group 2. They have 4, 20 and 88 electrons respectively and contain 2 valence electrons each and thus can lose two electrons to complete their octet. Thus they will show similar chemical properties.
The chemical reactivity of elements is governed by the valence electrons present in the element.
