Which describes the elements in a given period of the periodic table? A. They have similar chemical properties, such as chemical reactivity.

B. They have the same average atomic mass.

C. They are all in the same family.

D. They increase in atomic number sequentially from left to right.

A

Explanation:

Elements in the same group of the periodic table have similar chemical properties. Elements can be classified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals. Groups are numbered 1–18 from left to right.

P.S, All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, groups of elements in the same column have similar chemical and physical properties, reflecting the periodic law.