Question

How many basis functions will you have for hydrogen (H2) and water (H2O) if the 6- 31G** basis set is used? Please show your work.

Answer 1

STO -3G is a so called minimal basis set meaning that only one basis function is used for each atomic orbitals in the atom of which the molecule is made from .

The water molecules has two H atoms and one O atom with 1s11 and 1s222s222p66 electron configuration respectively when STO-3G is used would that then mean that three 1s type basis function and 3 type basis function are used each being made u from a linear combination (LC) of three simple Gaussians?

The 6-31+G**is a split - Valence basis set which includes both diffuse and polarisation function.