Chapter 5, Problem 77A

Interpretation Introduction

Interpretation:

The reason for one electron in a rubidium atom to occupy a $5s$ orbital rather than $4d$ or $4f$ orbitals needs to be explained.

Concept introduction:

Aufbau principle state that orbital with lower energy level are filled first than higher energy level orbitals.

Answer to Problem 77A

One electron of Rubidium atom occupies $5s$ because it has lower energy than $4d$ and $4f$

Explanation of Solution

Given Information: Rubidium atom

Energy diagram for all the sub levels shows that energy increases as we move upwards, it shows that the $5s$ sub level is below $4d$ and $4f$ sub levels it means that the $5s$ sub level has a lower energy than the $4d$ in $4f$

So one electron of rubidium atom occupies $5s$ rather than $4d$ and $4f$

Conclusion

One electron of Rubidium atom occupies $5s$ because it has lower energy than $4d$ and $4f$.