Question

is located in period 1. lithium (li) magnesium (mg) helium (he)

Explanation:

Step1: Recall periodic table knowledge

Elements in period 1 are hydrogen (H) and helium (He).

Step2: Analyze options

Lithium (Li) is in period 2, Magnesium (Mg) is in period 3, Helium (He) is in period 1.

Answer:

Helium (He)