3.5.2—The shapes of, and bond angles in, molecules

Predict an unfamiliar molecule or ion in a fixed order: identify the central atom, count its bonding pairs and lone pairs, treat each single/multiple bond as one electron domain, choose the electron-domain arrangement, and then name the molecular shape after omitting lone pairs from the visible atom layout.

Use the reference VSEPR arrangements to transfer the method to analogous species. For example, a central atom with five bonding domains and no lone pair gives a trigonal-bipyramidal arrangement, while four bonding domains around carbon give a tetrahedral arrangement. A central atom with three bonds and one lone pair has a pyramidal molecular shape.

Start from the ideal angle for the electron-domain arrangement, then explain deviations: lone pair–lone pair repulsion is strongest, lone pair–bonding pair repulsion is next, and bonding-pair repulsion is weakest. Multiple bonds count as one domain for shape, but their greater electron density can affect repulsion and angle comparisons.

Do not select a shape from the molecular formula alone or treat a lone pair as a bonded atom. The conclusion must follow from the central atom's domain count and the supported VSEPR comparison; do not infer an exact angle when the relevant arrangement or source-supported reference is not established.