VSEPR theory

Linear molecule (2 things around a central atom)

Linear molecule is a molecule in which atoms are deployed in a straight line (under 180° angle) Example carbon dioxide (O=C=O) and beryllium hydride BeH2

Tetrahedral (4 things around a central atom) Trigonal pyramidal

Tetrahedral is a molecular shape that results when there are four bonds and no lone pairs around the central atom in the molecule. The atoms bonded to the central atom lie at the corners of a tetrahedron with 109.5° angles between them. The ammonium ion (NH4+) and methane (CH4) have a tetrahedral molecular geometry.

Trigonal planar (3 things around a central atom)

Trigonal planar is a molecular shape that results when there are three bonds and no lone pairs around the central atom in the molecule. The pairs are arranged along the central atom's equator, with 120° angles between them. Molecules with an trigonal planar electron pair geometries have sp2d hybridization at the central atom. The carbonate ion (CO32-) has a trigonal planar geometry

VSEPR theory

Valance Shell Electron Pair Repulsion theory predicts the shapes of molecules and ions by assuming that the valence shell electron pairs are arranged as far from one another as possible.