Question

In each of the following sets of elements, indicate which element has the smallest atomic size. a. $\mathrm{Na},\mathrm{K},\mathrm{Rb}$ b. $\mathrm{Na},\mathrm{Si},\mathrm{S}$ c. $\mathrm{N},\mathrm{P},\mathrm{As}$ d. $\mathrm{N},\mathrm{O},\mathrm{F}$

Short answer

Based on the periodic trends, the elements with the smallest atomic size in each set are: a. $\mathrm{Na}$, b. $\mathrm{S}$, c. $\mathrm{N}$, and d. $\mathrm{F}$.

Step-by-step solution

Arrange the elements based on their positions in the periodic table

Compare the elements in each set based on their locations in the periodic table to understand their positions and use the trends to predict the smallest atomic size. a. $\mathrm{Na},\mathrm{K},\mathrm{Rb}$ are all alkali metals and belong to the same group (Group 1). b. $\mathrm{Na},\mathrm{Si},\mathrm{S}$ belong to the same period (Period 3). c. $\mathrm{N},\mathrm{P},\mathrm{As}$ belong to the same group (Group 15). d. $\mathrm{N},\mathrm{O},\mathrm{F}$ belong to the same period (Period 2).

Apply periodic trends to find the smallest atomic size

In each set, apply the trends discussed in the analysis section to determine the element with the smallest atomic size. a. In Group 1, atomic size increases down the group. Therefore, $\mathrm{Na}$ has the smallest atomic size among $\mathrm{Na},\mathrm{K}$, and $\mathrm{Rb}$. b. In Period 3, atomic size decreases from left to right. Therefore, $\mathrm{S}$ has the smallest atomic size among $\mathrm{Na},\mathrm{Si}$, and $\mathrm{S}$. c. In Group 15, atomic size increases down the group. Therefore, $\mathrm{N}$ has the smallest atomic size among $\mathrm{N},\mathrm{P}$, and $\mathrm{As}$. d. In Period 2, atomic size decreases from left to right. Therefore, $\mathrm{F}$ has the smallest atomic size among $\mathrm{N},\mathrm{O}$, and $\mathrm{F}$.

Conclusion

Based on the analysis of periodic trends, the elements with the smallest atomic size in each set are: a. $\mathrm{Na}$ b. $\mathrm{S}$ c. $\mathrm{N}$ d. $\mathrm{F}$