VSEPR

[duenezjuleny1D]

What is the difference between a vsepr formula and Lewis structures? What exactly is a vsepr formula supposed to look

[Ethan McCarthy 1F]

The VSEPR formula denotes the number of atoms and lone pairs connected to the central atom using ambiguous letters and numbers (A, X, and E, which still inform us of the molecule's geometry and shape).

A = the central atom
X = the number of atoms bonded to the central atom
E = the number of lone pairs on the central atom

For the molecular formula CH₄, the VSEPR formula is AX₄

For the molecular formula :NH₃, the VSEPR formula is AX₃E (where the one lone pair is implied by an "invisible" subscript 1 after the E)

[Eva Zhao 4I]

Lewis structures are 2-D representations of molecular shape and indicate the approximate location of bonding e- and lone pair e-.

The VSEPR Model, or the Valence-Shell Electron-Pair Repulsion Model, explains the experimentally observed shape of molecules. Note that the VSEPR Model can predict distortions qualitatively but not quantitatively.

The notation used in the VSEPR Model is:
A: Central atom
X: Bonded atom
E: Lone pair
As such, NH₃ is denoted AX₃E and H₂O is denoted AX₂E₂.