What are groups on the periodic table?

• A. Horizontal rows
• B. Vertical columns
• C. Blocks
• D. Diagonals

Answer: (B)

Groups are vertical columns on the periodic table. Elements in the same group have the same number of valence electrons, which gives them similar chemical properties and typical common oxidation states. For example, the alkali metals in one group all have one valence electron and tend to form +1 ions, while the halogens in another group have seven valence electrons and tend to form -1 ions. As you move down a group, the atoms get larger and their outer electrons are held a bit less tightly, reinforcing the idea that members of a group behave similarly. Horizontal rows are periods, and the blocks (s-block, p-block, d-block, f-block) describe which subshell is being filled, not groups. Diagonals aren’t used to define groups.