Question

1. choose the best answer.

what is the cause of the various molecular shapes?
the electrostatic repulsion of valence electrons
the electrostatic repulsion of atomic nuclei
the electrostatic attraction of atomic nuclei
the electrostatic attraction of valence electrons

1. choose the best answer.

what accounts for the differences between the trigonal planar and trigonal pyramidal molecular shapes?
lone pair of electrons on the central atom
a double bond on the central atom
a triple bond on the central atom
different number of bonded pairs on the central atom

Explanation:

Question 4

Molecular shapes are determined by the VSEPR theory, which is based on the electrostatic repulsion of valence electron pairs (bonding and non - bonding) around the central atom. Atomic nuclei are positively charged, and their repulsion is not the main factor for molecular shape. Also, attraction of atomic nuclei or valence electrons does not determine molecular shape. The electrostatic repulsion of valence electrons (bonding and lone pairs) causes them to arrange themselves in a way that minimizes repulsion, thus determining the molecular shape.

Trigonal planar molecules (e.g., $\ce{BF3}$) have three bonded pairs of electrons around the central atom and no lone pairs. Trigonal pyramidal molecules (e.g., $\ce{NH3}$) have three bonded pairs and one lone pair of electrons around the central atom. The lone pair of electrons on the central atom in trigonal pyramidal molecules exerts a greater repulsion than bonded pairs, which causes the bonded pairs to be pushed down, resulting in the pyramidal shape. A double or triple bond on the central atom is not the cause of the difference between these two shapes, and they have the same number of bonded pairs (three).

Answer:

the electrostatic repulsion of valence electrons

Question 5