Which best describes the sequence of the elements in period 5 of the periodic table?

• A. It begins with an alkali metal and proceeds through alkaline earth metals, transition metals, metalloids, and ends with a noble gas.
• B. It starts with a transition metal and ends with a halogen.
• C. It consists entirely of nonmetals.
• D. It contains only representative elements and no transition metals.

Answer: (A)

Verified step by step guidance

1. Recall that a period in the periodic table is a horizontal row of elements, and period 5 specifically contains elements with atomic numbers from 37 (Rubidium) to 54 (Xenon).
2. Identify the types of elements in period 5 by their groups: it starts with group 1 (alkali metals), followed by group 2 (alkaline earth metals), then the transition metals (groups 3 to 12), metalloids, and ends with the noble gases (group 18).
3. Understand that period 5 includes a variety of element types: metals (alkali, alkaline earth, and transition metals), metalloids, and nonmetals, showing a progression across the period.
4. Recognize that the sequence does not start with transition metals nor does it consist entirely of nonmetals; it also includes transition metals, so it is not limited to only representative elements.
5. Conclude that the best description of the sequence in period 5 is that it begins with an alkali metal, proceeds through alkaline earth metals, transition metals, metalloids, and ends with a noble gas.