Chapter 5, Problem 78A

Interpretation Introduction

Interpretation:

The term valence electrons needs to be explained and the number of valence electrons of magnesium atom needs to be determined.

Concept introduction:

Electrons which are present in the outer most orbital of an atom refer to as valence electron.

Answer to Problem 78A

Electrons of outer most orbital of an atom refer to as valance electron

The magnesium atom has 2 valence electrons.

Explanation of Solution

Given information:

Magnesium atom.

Electrons of outer most orbital of an atom refer to as valence electron.

The electron configuration of magnesium is $1s^{2}2s^{2}2p^{6}3s^2$

The outermost orbital of magnesium is $3s.$ it has two electrons. Thus the valence electron in magnesium is $2$.

Conclusion

The magnesium atom has $2$ valence electron.