Question

Which of the following substances has only one type of atom? A. Water B. Salt C. Sand D. Oxygen

Answer 1

`D.`

Explanation:

Oxygen has only one type of atom, which is oxygen of course!

Water has a chemical formula of `H_2O`. As you can see here, it's made up of two types of atoms, hydrogen and oxygen, so this is not an answer.

Salt has a chemical formula of `NaCl`. As with water, it is also made up of two types of atoms, sodium and chlorine atoms, so it's not an answer. Even if you talk about salts made from a reaction, they are still made up of two or more different elements.

Sand is a mixture, and it does not have a chemical formula! It is made up of many different substances, so it is `100%` not made up of only one type of atom.

So, option `D.` is correct.