Question

which atmospheric gas is the lightest because it only has one proton and one electron and is made of only one element? ozone argon hydrogen methane

Explanation:

Hydrogen has one proton and one electron and is a single - element gas, making it the lightest among common atmospheric gases. Ozone ($O_3$), argon (Ar), and methane ($CH_4$) are heavier.

Answer:

C. hydrogen