Here's how to determine the number of atoms in a molecule of Na₂SO₄:

* Na₂SO₄ represents sodium sulfate.

* Subscripts indicate the number of atoms:

* Na₂: Two sodium (Na) atoms

* S: One sulfur (S) atom

* O₄: Four oxygen (O) atoms

Therefore, a molecule of Na₂SO₄ contains a total of 7 atoms (2 + 1 + 4).