Chapter 6, Problem 42A

Interpretation Introduction

Interpretation:

The relation of energy level of an atom’s valence electrons to its period in the periodic table needs to be explained.

Concept introduction:

The number of electrons in the valence shell of an atom is called valence electrons. In an atom, different energy levels present where electrons are filled using Aufbau principle.

Answer to Problem 42A

The highest energy level indicates the period number of the element.

Explanation of Solution

From the electronic configuration of an element, its group and period can be known. The number of highest energy level indicates the period number and for representative elements, the number of valence electrons indicates the group number. Let’s take example of Fluorine which electronic configuration is, $1s^{2}2s^{2}2p^5$. The number of highest energy level 2p⁵ indicates that fluorine is present in 2^nd period.

Conclusion

The period number of an element can be known if the highest energy level is known.