Answer
a. Group 1A (1) - Alkali metals.
b. Second period.
c. Group 8A (18) - Noble gases.
d. Group 7A (17) - Halogens.
Work Step by Step
See Figure 4.1, the Periodic Table of Elements for visual reference.
a. Na, K and Rb are all on the first column of the periodic table. Since columns represent groups, the group that contains these three elements is the Group 1A (1), which is known as Alkali metals.
b. Lithium (Li) is the second element of the first column, and the first element of the second row, which is the second period.
c. Noble Gases is a special name for the Group 8A (18).
d. F, Cl, Br and I are all on the 17$^{th}$ column of the periodic table. Since columns represent groups, the group that contains these four elements is the Group 7A (17), which is know as Halogens.
