The figure that follows contains ball-and-stick drawings of...

The figure that follows contains ball-and-stick drawings of three possible shapes of an $\mathrm{AF}_{4}$ molecule. (a) For each shape, give the electron-domain geometry on which the molecular geometry is based. (b) For each shape, how many nonbonding electron domains are there on atom $A$ ? (c) Which of the following elements will lead to an $\mathrm{AF}_{4}$ molecule with the shape in (iii): Be, C, S, Se, Si, Xe? (d) Name an element A that is expected to lead to the $\mathrm{AF}_{4}$ structure shown in (i).

Key Concepts

VSEPR Theory

This theory (Valence Shell Electron Pair Repulsion) explains how electron pairs arrange themselves around a central atom in order to minimize repulsion. It is used to predict molecular geometries based on the total number of electron domains, including both bonding pairs and lone pairs.

Electron-Domain Geometry

This concept refers to the three-dimensional arrangement of all electron domains (bonding and nonbonding electron pairs) around a central atom. It provides a basis for determining the idealized shape of the electron cloud and is crucial for predicting the overall geometry of molecules.

Molecular Geometry

Molecular geometry describes the actual arrangement of the atoms in a molecule, taking into account the positions of only the nuclei. It is derived from the electron-domain geometry after accounting for the repulsive influence of any lone pairs, which can alter bond angles and distort the idealized shape.

Lone Pairs

Lone pairs are nonbonding pairs of electrons localized on the central atom. Their presence in the electron-domain geometry affects the molecular shape by repelling bonding pairs more strongly than bonding pairs repel each other, often leading to deviations from ideal bond angles.

Periodic Trends in Element Behavior

Periodic trends, such as differences in electronegativity, orbital availability, and electron configuration, influence how central atoms in molecules like AF4 accommodate bonding and nonbonding electron domains. These trends help explain why different elements prefer different molecular shapes based on their ability to minimize electron repulsion and satisfy bonding requirements.

Transcript

00:01 All right, guys.

00:02 Problem number 28 of chapter 9 in chemistry, central science.

00:06 So the figure that you see here contains bolns shows three possible shapes of an af4 molecule.

00:14 For each shape, give the electron domain geometry on which the molecule, on which the molecular geometry is based.

00:25 So let me try to separate these.

00:36 So this is a square planar structure.

00:45 Oh, sure? so that's evident that it has four bonds and two long pairs.

00:55 So its electron domain geometry would be octahedral.

01:17 All right, for this one, this is a tetrahedral molecular geometry, and tetragil is also the electron domain geometry.

01:35 And for the third one, that is a seesaw structured, and that's a trigonal bipyramid electron domain geometry.

02:14 So part b, for each shape, how many non -bonding electron domains are there on atom a? so this is octahedral.

02:21 So there are, then we have four bonds.

02:25 That means we have two non -bonding domains.

02:28 Here we have zero because it's tetrahedral, both molecular and electron domain geometry.

02:37 And since this is trigonal biphem electron domain geometry, we have one.

02:44 Non -bonded pair, one loan pair.

02:47 So for part c, they want to know which of the following elements will lead to an a4 molecule in shape 3.

02:57 So i'm going to move, going to get rid of this.

03:05 So in fact, let me draw this.

03:09 Just this loan pair should be there.

03:23 So let's see.

03:27 Let's draw our domain structure.

03:36 Two, three.

03:56 So we have to take.

03:58 Count how many electrons we have...

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