Final answer:
The alkali metals have their highest energy electrons in an s orbital, making option (e) the correct answer.
Step-by-step explanation:
The alkali metals, represented by option (e), have their highest energy electrons in an s orbital. Alkali metals are found in Group 1 of the periodic table and have one electron in the outermost s orbital. These elements are highly reactive, easily losing their outermost electron to form a singly positive ion. Examples of alkali metals include sodium (Na) and potassium (K).