In molecules with the same number of electron groups but different molecular geometries, One of the chances is that the central atoms alter in the way in which their electrons are arranged.
Explanation:
Consider molecules with steric number = four sets of electrons around the central atom.A tetrahedral geometry with 109.5 deg bond angles is predicted by VSEPR
NH3 is pyramidal with a lone pair on one end of the tetrahedron. The HNH angle is 107.3 deg, generally described by stating that the lone pair is fatter than the pairs that bond.
PH3 is also pyramidal, the HPH angles are close to being 90-degree angles.
The assumption is that the small atoms (like C and N) use hybrid sp3 orbitals to form the bonds with hydrogen in their compounds. All N and P merely make three ammonia and phosphine bonds.
The hydrogens remain further apart if the nitrogen uses hybrid orbitals. Phosphorus is large enough that the hydrogens don’t associate too much in phosphine. Since the P doesn’t have to exhaust the energy required to hybridize its bonding orbitals.
An element, by definition, always has the same number of protons. Sodium, element 11, has 11 protons. Anything with 11 protons is a sodium atom, regardless of the number of neutrons, electrons, or politicians.
