Chapter 8, Problem 19STP

Interpretation Introduction

Interpretation: The number of electrons present in beryllium ion’s outer energy level is to be stated.

Concept introduction: The strategy for drawing Lewis structure is mention below.

• Calculate the number of valence electrons present in the molecule.
• Calculate the electron pairs by diving number of valence electrons by 2.
• Determine the bond pairs.
• Determine the lone pairs.
• Check whether the central atom satisfies octet rule.

Answer to Problem 19STP

The number of electrons present in beryllium ion’s outer energy level is zero (0). Therefore, option (A) is the correct option.

Explanation of Solution

Reason for correct option: The atomic number of beryllium is 4. The electronic configuration of beryllium is $1s^{2}2s^2$ . The outer most energy level is $2s$ . The number of electrons present in outer most energy level is 2. The beryllium releases two electrons to form beryllium ion $\left({\text{Be}}^{\text{2}+}\right)$ and reaches noble gas configuration (chemically stable). Therefore, the electronic configuration of beryllium ion $\left({\text{Be}}^{\text{2}+}\right)$ is $1s^{2}2s^0$ . Therefore, the number of electrons present in beryllium ion’s outer energy level is zero (0). Therefore, option (A) is the correct option.

Conclusion

Reason for incorrect option: The number of electrons present in beryllium ion’s outer energy level is zero. So, B, C, D and E are incorrect options.