Calcium sulfate is a compound, not an element, so it doesn't have an atomic number.

Atomic numbers refer to the number of protons in the nucleus of an atom. Compounds are made up of two or more elements chemically bonded together.

Here's what you can do to understand the composition of calcium sulfate:

* Chemical formula: Calcium sulfate has the formula CaSO₄. This means it's composed of one calcium atom (Ca), one sulfur atom (S), and four oxygen atoms (O).

* Atomic numbers of elements:

* Calcium (Ca): Atomic number 20

* Sulfur (S): Atomic number 16

* Oxygen (O): Atomic number 8

Let me know if you have any other questions!