Final answer:
A molecule with one lone pair and three bonded atoms using the octet rule will exhibit a tetrahedral electron-pair geometry and an sp³ hybridization, resulting in a pyramidal physical structure. The correct answer is 4. tetrahedral; sp³.
Step-by-step explanation:
The molecule described, having one lone pair of electrons on the central atom and three atoms bonded to the central atom while following the octet rule, has a tetrahedral electron-pair geometry. Since there are four regions of electron density (three bonding pairs and one lone pair), the central atom will be sp³ hybridized.
The physical structure, however, will be pyramidal due to the lone pair causing a distortion of the tetrahedral geometry.
The molecule with one lone pair of electrons on the central atom and three atoms bonded to the central atom has a tetrahedral electron arrangement and sp³ hybridization.
This means that the central atom is surrounded by four regions of electron density and needs four identical sp³ hybrid orbitals to accommodate these regions. Each of these hybrid orbitals points towards a different corner of a tetrahedron.