How many types of atoms make up a particle of water?

Water's chemical name is H20 because it has 1 Hydrogen and 2 Oxygen atoms in each molecule. But only pure water is composed of this, so if it comes from the tap, it is impure, meaning it has other minerals in it. That's why we can "taste" water, we actually taste the impurities in it, but pure water has 2 different types of atoms.

Answer 2

Water is made of two different elements; hydrogen and oxygen.

However it is not quite as simple as to say that therefore water is made up only of 2 different types of atoms because each element has what are known as isotopes.

An isotope is a variation of an atom of a specific element. It is where the atom contains a different number of neutrons inside the nucleus.

There are 2 hydrogen isotopes which occur in water: hydrogen 1 & hydrogen 2 (deuterium).

There are 3 oxygen isotopes which occur in water: oxygen 16, oxygen 17 & oxygen 18.

So, the vast majority of atoms in water will be made from just hydrogen 1 & oxygen 16, but in any given amount of water there may be up to 5 different types of atoms present.