What is the chemical formula for ammonium sulfide

The chemical formula for ammonium sulfide is (NH4)2S

The chemical formaula for ammonium sulfide would be ammonium (NH₄⁺) plus sulfur (S⁺²). So now what we would do is figure out how to balance the charges (to create a stable molecule) using our knowledge of valence electrons. Or we can use a shortcut and switch the subscripts of the two atoms so it looks like this: (NH₄)₂S.

(We used a shortcut, but essentially what we did was figure out how many of each atom/ion we would need to create a balanced molecule.)

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.