Lithium, sodium, and potassium belong to which group on the periodic table?

• A. Group 1, the alkali metals
• B. Group 17, the halogens
• C. Group 18, the noble gases
• D. Group 3, the boron group

Answer: (A)

Understanding how elements are grouped helps explain why these three sit together. Each of lithium, sodium, and potassium has exactly one electron in its outer shell, so they share the same tendency to lose that electron and form a +1 ion. That single-electron outer configuration gives them very similar properties: they’re soft, light metals with low melting points and, notably, they react strongly—more so as you move down the group. This family is called the alkali metals, which is the clue that links them. The other options describe different families: halogens are nonmetals with seven valence electrons, noble gases have full outer shells and are very unreactive, and the boron group has three valence electrons and distinct chemistry. So lithium, sodium, and potassium belong to the alkali metals group.