Chapter 6.3, Problem 18PP

Interpretation Introduction

Interpretation:

The element with large atomic radius of the two unknown elements needs to be determined; if the atomic number of one of the element is 20 greater than the other.

Concept introduction:

The distance from centre of the nucleus to the valence shell containing the valence electrons is atomic radius. In moving across a period, the atomic size of the elements decreases and down the group the atomic size increases.

Answer to Problem 18PP

No, the element of larger atomic radius cannot be identified from the given information.

Explanation of Solution

The two unknown elements are given and one of the elements has atomic number 20 more than the other. The 20 more atomic number of one element than the other indicates that both the elements are not in same group or period. The identification of the element of larger atomic radius is possible only when both the elements are in same period or group. So, the element whose atomic radius is larger cannot be identified.

Conclusion

Across a period, the atomic radius of elements decreases and down the group the atomic radius increases.