Question

question 1 (10 points) what is the total number of electron domains around the central atom for a molecule having a square pyramidal molecular geometry, such as clf₅? a) 5 b) 2 c) 3 d) 4 e) 6

Explanation:

Step1: Recall VSEPR Theory

For a molecule with square pyramidal molecular geometry (like $\ce{ClF5}$), we use the Valence - Shell Electron - Pair Repulsion (VSEPR) theory. The central atom in $\ce{ClF5}$ is $\ce{Cl}$. Chlorine has 7 valence electrons. Each fluorine atom contributes 1 valence electron, and there are 5 fluorine atoms. So the total number of valence electrons around the central $\ce{Cl}$ atom is $7 + 5\times1=12$. But when considering electron domains, we look at the number of bonding pairs and lone pairs. In $\ce{ClF5}$, the central $\ce{Cl}$ atom forms 5 bonding pairs with $\ce{F}$ atoms and has 1 lone pair. The number of electron domains is the sum of bonding domains and lone - pair domains. So the number of electron domains $=5 + 1=6$? Wait, no, wait. Wait, square pyramidal molecular geometry is associated with a total of 6 electron domains? No, wait, no. Wait, the electron - domain geometry for square pyramidal is octahedral? No, wait, no. Wait, let's re - calculate. The central atom $\ce{Cl}$ in $\ce{ClF5}$: the number of valence electrons of $\ce{Cl}$ is 7. The number of electrons it shares: each $\ce{Cl - F}$ bond is a single bond, so 5 bonds mean 5 shared pairs (10 electrons). The number of lone - pair electrons on $\ce{Cl}$: $7-5 = 2$? Wait, no, that's wrong. Wait, the formula for calculating the number of electron domains (steric number) is: steric number $=\frac{\text{valence electrons of central atom}+\text{number of atoms bonded to central atom}-\text{charge (if any)}}{2}$ (for neutral molecules). For $\ce{ClF5}$, central atom $\ce{Cl}$ has 7 valence electrons, bonded to 5 $\ce{F}$ atoms. So steric number $=\frac{7 + 5}{2}=\frac{12}{2}=6$. So the total number of electron domains (bonding + lone - pair) is 6. But wait, the molecular geometry is square pyramidal, which comes from an octahedral electron - domain geometry (6 electron domains) with one lone pair. So the total number of electron domains around the central atom is 6.

Step2: Match with Options

Looking at the options, option E is 6.

Answer:

E) 6