Question

multiple select question
select all that apply
the first row of the periodic table

□ does not include an element with a full outer energy level
□ has elements with electrons in just one energy level
□ includes just two elements: hydrogen and helium

need help? review these concept resources.
read about the concept

Explanation:

• Helium (\(He\)) in the first row has a full outer energy level (2 electrons in the \(1s\) orbital), so the first option is incorrect.
• The first - row elements (\(H\) and \(He\)) have electrons only in the first energy level (\(n = 1\)).
• The first row of the periodic table contains only two elements: hydrogen (\(H\)) and helium (\(He\)).

Answer:

• B. has elements with electrons in just one energy level
• C. includes just two elements: hydrogen and helium