Molecular Geometry

Concept: Chemistry (Chemical Bonding) - VSEPR Theory.

Step 1: Identify the central atom and its valence electrons. The central atom in the molecule is Phosphorus (P). Phosphorus is located in Group 15 of the periodic table, which means it has 5 valence electrons in its outermost shell.

Step 2: Determine the number of bond pairs (BP). The chemical formula indicates that the central phosphorus atom is bonded to 5 surrounding chlorine (Cl) atoms. Each bond is a single covalent bond. Therefore, the number of bond pairs (BP) is 5.

Step 3: Calculate the number of lone pairs (LP). The number of lone pairs on the central atom can be calculated by subtracting the number of shared electrons from the total valence electrons and dividing by two. Since all 5 valence electrons of phosphorus are used to form the 5 single bonds with chlorine, there are electrons remaining. Thus, the number of lone pairs (LP) is 0.

Step 4: Determine the steric number and electron geometry. The steric number is the sum of the bond pairs and lone pairs: . According to Valence Shell Electron Pair Repulsion (VSEPR) theory, a steric number of 5 corresponds to a trigonal bipyramidal electron geometry to minimize electron repulsion.

Step 5: Determine the final molecular geometry. Because there are zero lone pairs on the central phosphorus atom, there is no distortion to the underlying electron geometry. The arrangement of the atoms precisely follows the arrangement of the electron domains.
Therefore, the molecular geometry is identical to the electron geometry, which is perfectly trigonal bipyramidal, with three equatorial bonds at to each other and two axial bonds at to the equatorial plane. $ $

Concept: Hybridization depends on the steric number, which is the total number of sigma bonds and lone pairs around the central atom.

Step 1: Identify bonding in . Sulfur is the central atom and forms bonds with six fluorine atoms.

Step 2: Determine steric number.

Step 3: Determine hybridization. Steric number corresponds to This gives an octahedral geometry. Thus, the hybridization of sulfur in is

Concept: Dipole moment is a measure of the separation of positive and negative charges in a molecule. The overall dipole moment depends on both bond polarity and molecular geometry. If the bond dipoles cancel each other due to symmetry, the molecule has zero net dipole moment.

Step 1: Examine molecular shapes.

• : Trigonal pyramidal shape due to one lone pair on nitrogen.
• : Bent or V-shaped geometry due to two lone pairs on oxygen.
• : Trigonal pyramidal geometry similar to ammonia.
• : Tetrahedral and highly symmetrical.

Step 2: Effect of symmetry on dipole moment.
In , four identical bonds are arranged symmetrically around the carbon atom in a tetrahedral geometry. The dipole moments of these bonds cancel each other.

Step 3: Conclusion.
Since the bond dipoles cancel perfectly in , it has zero net dipole moment.