Question

Why does calcium have a positive valency?

Answer 1

a calcium has an atomic numberequal to 20, which means that it contains 20protons inside its nucleus. This means that aneutral calcium atom has 20 electrons surrounding its nucleus.

The electron configuration of a neutral calcium atom looks like this

Ca: 1s22s22p63s33p64s2

As you can see, a neutral calcium atom has 2valence electrons. You can tell by looking at the number of electrons present in the outermost energy shell of the atom, i.e. in the valence shell.

In this case, calcium's outermost energy level, which corresponds to n=4, contains 2 electrons.

Now, in order to complete its octet, i.e. get 8electrons in its outermost shell, calcium losesthose 2 electrons. The resulting calcium ion will have a 2+ charge because it contains

the same number of protons as the neutral atomtwo electrons less than the neutral atom