Molecular Shape

[Steven Garcia 1H]

If a molecule has a single central atom and three bonds for three other atoms (therefore three regions of high electron concentration), how do we determine whether this molecule has a trigonal planar-, trigonal pyramidal-, or t- shape?

[Kessandra Ng 1K]

The distinction between the 3 shapes you named are the number of lone pairs on the central atom, as the electron-electron repulsion by the lone pair of electrons will cause the other atoms to shift closer to each other; thus, the number of lone pairs on the central atom affects the shape of the entire molecule and the angles between each atom.

Trigonal planar: 0 lone pairs on the central atom

Trigonal pyramidal: 1 lone pair on the central atom

T-shaped: 2 lone pairs on the central atom.

[404905747]

Does this mean that you can determine the shape just by looking at how many lone pairs a molecule has?

[Kessandra Ng 1K]

This means you can determine the shape by looking at the number of atoms the central atom bonds to, and also the number of lone pairs of electrons on the central atom. Those are the 2 main factors in determining shape.

[LeannaPhan14BDis1D]

is there any other challenging molecule someone can provide as an example to help further help with my knowledge on how the shapes and angles work?