What is the shape of the hypothetical molecule XY3

Trigonal planar

Explanation:

If a hypothetical molecule XY3 has three electron domains as shown and no lone pairs, the molecule will be trigonal planar in shape.

From the valence shell electron pair repulsion theory, the shape of molecules is dependent on the number of electron domains in a molecule and weather those electron pairs are lone pairs or bond pairs.

Since lone pairs cause more repulsion and take up more space around the central atom than bond pairs, bond pairs cause the bond angle and molecular geometry to deviate from that predicted on the basis of the valence shell electron pair repulsion theory.

Finally, remember that in a molecule, electron pairs are placed as far apart in space as possible to minimize repulsion.