A central atom in a molecule has two lone pairs of electrons and forms three single bonds. The shape of this molecule is:

The shape of this molecule is trigonal pyramidal.

Here's the step-by-step reasoning:

1. First, we need to determine the steric number, which is the number of atoms bonded to the central atom plus the number of lone pairs of electrons. In this case, the central atom forms three single bonds and has two lone pairs of electrons, so the steric number is 5.

2. Next, we need to determine the molecular geometry. This is based on the steric number and the number of lone pairs. For a molecule with a steric number of 5 and two lone pairs, the molecular geometry is trigonal pyramidal.

So, the shape of the molecule is trigonal pyramidal.