Question

which element behaves the most like calcium and why?
k, because it is in the same period and only has one less valence electron.
ba, because it is in the same group and has same number of valence electrons.
br, because it is in the same period and has more valence electrons.
sc, because it is in the same period and has one more valence electron.

Explanation:

Elements in the same group have similar chemical properties due to the same number of valence electrons. Calcium and Beryllium are in Group 2.

Answer:

Be, because it is in the same group and has same number of valence electrons.