Chapter 5, Problem 17STP

Interpretation Introduction

Interpretation:

The correct orbital diagram for beryllium element needs to be determined.

Concept introduction:

According to the Aufbau principle in the ground state, an electron first enters the lowest energy level and further electrons are added to the orbitals with increasing energies.

Answer to Problem 17STP

Correct answer: The correct option is B.

Explanation of Solution

Reason for correct option:

According to the Aufbau principle, the electron first enters into the lowest energy level. The options are as follows:

Beryllium contains four electrons and its electronic configuration is $1s^{2}2s^2$.

Therefore, the diagram that contains total four electrons is option B.

Conclusion

Reason for incorrect options:

1. The total number of electrons is only 2 but in beryllium the number of electrons is 4 thus, option A is incorrect.

C. The total number of valence electrons is 7 but in beryllium the number of electrons is 4 thus, option C is incorrect.

D. The given electronic configuration cannot be true for any element as it does not follow Aufbau principle. Thus, option D is incorrect.