Which of the following does not represent a compound?

NaCl
N20
CO2
O2

D. O2

Explanation:

First, let’s define a compound.

A compound is a substance made when 2 or more elements are chemically combined in a fixed ratio.

Now, let’s examine the answer choices.

A. NaCl

• This has sodium (Na) and chlorine (Cl) so it is a compound.

B. N2O

• This has nitrogen (N) and oxygen (O). This is a compound.

C. CO2

• This has carbon (C) and oxygen (O) so this is also a compound.

D. O2

• This only has oxygen (O). A compound needs two or more elements, so this is not a compound.

Therefore, the correct answer is D. O2