Equations

This page shows an equation. Conventionally, equation numbers should be on the right side.

(1)$$\begin{array}{r}\begin{array}{c}\hat{H}\mathrm{\Psi }=E\mathrm{\Psi }\\ \hat{H}=-\frac{1}{2}{\mathrm{\nabla }}^2-\frac{1}{r}\end{array}\end{array}$$