Question

which substance is made of only one type of atom?
a fire
b air
c water
d element

Explanation:

• Fire is a chemical reaction (exothermic oxidation) and not a substance made of atoms.
• Air is a mixture of gases like nitrogen (\(N_2\)), oxygen (\(O_2\)), carbon - dioxide (\(CO_2\)) etc., so it has different types of atoms (\(N\), \(O\), \(C\) etc.).
• Water (\(H_2O\)) is a compound made of hydrogen (\(H\)) and oxygen (\(O\)) atoms.
• An element is a pure substance that is made of only one type of atom. For example, gold (\(Au\)) is made of only gold atoms, and iron (\(Fe\)) is made of only iron atoms.

Answer:

d. element