The most electropositive element among the alkaline earth metals is:
A. Be
B. Mg
C. Ca
D. Ba

Hint: Electronegative elements are those elements who can easily attract a pair of electrons whereas an electropositive element is that element who can easily lose the outermost electron from the valence shell.

Complete step by step answer:
- The trend of electropositive and atomic size in the group is different.
- When we move down the group, atomic size increases due to an increase in the number of the shells.
- The given compound in the question is all alkaline earth metals.
- Also, due to the increase in the atomic size and number of shells the effective nuclear charge decrease and the attraction of the electron towards the nucleus.
- Hence, the electron can be easily lost.
- As we know that the atomic number of beryllium, magnesium, calcium and barium are 4, 12, 20 and 56.
- So, we can see that the barium has the largest atomic no. and has maximum no. of shells in the atom.
- So, among Be, Mg, Ca and Ba, Barium has the largest size due to which it can easily lose the outermost electron from the shell and will be considered as the most electropositive element.
- Barium is an element and it is placed in group 2 of alkaline earth metals.

So, the correct answer is “Option D”.

Note:
In the whole periodic table, fluorine is considered as the most electronegative element. Fluorine belongs to the first element of the group 17 and has the smallest size due to which it has the maximum value of effective nuclear charge and cannot lose electrons easily.