There is a chemical bond in the ammonium ion NH4.

In the ammonium ion (NH4) +, the bond is covalent polar. A covalent polar bond occurs when the atoms in a molecule do not differ much in electronegativity. The total pair of electrons will shift to a more electronegative element and an excess of negative charge will appear on it, and an excess of positive charge on a less electronegative one. By this mechanism, three hydrogen atoms in the ammonium ion are attached. The fourth atom is attached through a kind of covalent polar bond – the donor-acceptor mechanism, which occurs because hydrogen does not have a 1s orbital filled, and nitrogen has a lone pair of electrons.