Chapter 7, Problem 100A

Interpretation Introduction

Interpretation:

The reason for calcium forming ${\text{Ca}}^{2+}$ and not ${\text{Ca}}^{3+}$

Concept introduction:

The electronic configuration of different elements is defined by arranging the electrons in different energy levels. There is a standard format for filling up electrons in the sub shells. The electronic configuration is written using principal quantum number, n. Each energy level is identified using s, p, d, f and number of electrons are written as superscript. The outermost electrons are said to be valence electron which can be transferred or shared in order to complete their octet and achieve stability. Also depending on the valence electrons, the number of transfer of electrons are determined.

Answer to Problem 100A

Calcium can form ${\text{Ca}}^{2+}$ and not ${\text{Ca}}^{3+}$ as removal of two electrons will give a stable structure rather than removal of 3 electrons.

Explanation of Solution

The atomic number of Calcium is 20 and its electronic configuration is ${\text{1s}}^2{\text{2s}}^2{\text{2p}}^6{\text{3s}}^2{\text{3p}}^6{\text{4s}}^2$. It has two valence electrons in its outermost energy shells. Calcium can donate these two electrons and complete its octet.

But if one more electron has to be removed it will be removed from 3p energy level. In such a case, it will leave with 5 electrons which is an unstable energy level. Hence, Calcium cannot remove 3 electrons.

Conclusion

Calcium can form ${\text{Ca}}^{2+}$ and not ${\text{Ca}}^{3+}$ as removal of two electrons will give a stable structure rather than removal of 3 electrons.