The molecular formula of potassium permanganate is KMnO₄.
Potassium permanganate is an ionic compound. It consists of the potassium ion, K⁺, and the permanganate ion, MnO₄⁻.
Permanganate ion is a polyatomic ion. You will have to memorize the names and formulas of several polyatomic ions. Here is a brief list.
The potassium ion has a charge of +1, and the permanganate ion has a charge of -1. To make the overall charge zero, one K⁺ ion combines with one MnO₄⁻ ion.
Thus, the molecular formula of potassium permanganate is KMnO₄.
Hope this helps.
Here is a video of a demonstration which combines glycerin, potassium permanganate and water. The potassium permanganate is a strong oxidizing agent - which you can tell after viewing the video!
video from: Noel Pauller