Chapter 24, Problem 97A

Interpretation Introduction

Interpretation:

Reason for presence of 8 elements in second period is to be explained.

Concept introduction:

The modern periodic table is arranged in order of increasing atomic number and the elements of the similar properties are placed in the same group. In modern periodic table, there are 18 groups and 7 periods.

Answer to Problem 97A

8 elements are there in second period because every element has electrons in second shell with maximum 8 electrons and no electron enters in third shell.

Explanation of Solution

Elements are arranged into periods based on which electron shell is being filled. In the second period, the second shell is being filled. 8 elements are there in second period because every element has electrons in second shell with maximum 8 electrons and no electron enters in third shell.

The first element of second period is Lithium and last element is Neon with electronic configuration as shown respectively.

Electronic configuration of $\text{Li}$ is $\left[\text{He}\right]{\text{2s}}^{\text{1}}{\text{2p}}^{\text{0}}$ with atomic number 3.

Electronic configuration of $\text{Ne}$ is $\left[\text{He}\right]{\text{2s}}^2{\text{2p}}^6$ with atomic number 10.

Conclusion

8 elements are there in second period because every element has electrons in second shell with maximum 8 electrons and no electron enters in third shell.