Question 6.9: Using only the periodic table, rank the following elements i......
Using only the periodic table, rank the following elements in order of increasing size: Fe, K, Rb, S, and Se.
Strategy We want to arrange the elements from smallest to largest. Begin by finding each element in the periodic table. Then use the general trends for atomic size to place them in the requested order.
Atomic radius increases as we go from top to bottom or right to left in the periodic table. Sulfur and selenium are both in Group 16; because sulfur is above selenium, it will be smaller. Similarly, the positions of rubidium and potassium in Group 1 tell us that potassium is the smaller of the two. Finally, potassium, iron, and selenium are in the fourth period. Selenium is the rightmost of the three, so it will be the smallest, followed by iron and then potassium. Putting all these facts together gives us the requested order: S < Se < Fe < K < Rb.
Check Your Understanding Using only the periodic table, rank the following elements in order of increasing size: Cr, Cs, F, Si, and Sr.