Chapter 8, Problem 83A

Interpretation Introduction

Interpretation:

The number of valence electrons in N, As, Br and Se and covalent bonds for each of these elements to satisfy the octet rule needs to be explained

Concept introduction:

Noble gases show stable electron arrangement. This stable arrangement contains complete outer energy level and smaller potential energy compared to other electron arrangement.

Answer to Problem 83A

Number of valence electrons and covalent bond for completing their octet for each element listed below:

Valence electron Covalent bond

N: $5$ $3$

As: $5$ $3$

Br: $7$ $1$

Se: $6$ $2$

Explanation of Solution

In the periodic table, number of valance electrons of the elements is same as the group number. Number of electrons needed for satisfying the octet is calculated as follows:

$\text{number}\text{of}\text{electrons}\text{needed}=8-\text{number}\text{of}\text{valence}\text{electrons}$

Valence electrons in N is $5$. Hence, number of electrons to completely filled their octet is $8-5=3$.

Valence electrons in As is $5$. Hence, number of electrons to completely filled their octet is $8-5=3$.

Valence electrons in Br is $7$. Hence, number of electrons to completely filled their octet is $8-7=1$.

Valence electrons in Se is $6$. Hence, number of electrons to completely filled their octet is $8-6=2$.

Conclusion

An element achieves stable electronic configuration if the outermost shell holds eight electrons.