how many types of atom are contained in an element?

For a single chemical element, there is only one type of atom.

Quick Scoop

An element is defined as a substance made of only one kind of atom, so a sample of a pure element contains atoms that all have the same number of protons in their nuclei.

That proton number (the atomic number) is what makes it that element and not another.

You might hear about isotopes of an element, which are atoms of the same element that have different numbers of neutrons, but they are still atoms of the same element, just heavier or lighter versions.

So for the usual school-style question “How many types of atom are contained in an element?”, the intended answer is 1.

In other words: one element → one kind of atom (though it can have several isotopes that are all still that element).

TL;DR: A chemical element contains only one type of atom, defined by its unique number of protons.

Information gathered from public forums or data available on the internet and portrayed here.