Identify the electron pair geometry and the molecular...

Key Concepts

Molecular Geometry

Molecular geometry, or molecular structure, describes the arrangement of only the bonding pairs around the central atom, ignoring lone pairs. This geometry represents the actual shape of the molecule as it would be observed experimentally and determines many of the molecule's physical and chemical properties.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the three-dimensional arrangement of atoms in a molecule based on the number of electron domains (both bonding pairs and lone pairs). It posits that electron pairs repel each other, and thus, they try to occupy positions in space that minimize these repulsions, which guides the overall geometry of the molecule.

Electron Pair Geometry

Electron pair geometry refers to the spatial arrangement of all electron density regions (bonding pairs and lone pairs) around a central atom. This concept is crucial for understanding how atoms and electron groups arrange themselves in space to minimize repulsion, regardless of whether the electrons are involved in bonding.

Steric Number

The steric number is the total count of atoms or electron groups attached to a central atom, including both bonding pairs and lone pairs. It is a fundamental concept in VSEPR theory that helps determine the electron pair and molecular geometries of a molecule.

Effect of Lone Pairs

Lone pairs are non-bonding electron pairs that, due to their higher electron density compared to bonding pairs, exert greater repulsive forces. This leads to distortions in the ideal bond angles and influences the molecular shape, often making the observed geometry differ from the geometric pattern predicted solely by the steric number.

Transcript

00:01 So in this problem, we are asked to find the molecular geometry and electron pair geometry of each of the following molecules or polyethomic ions.

00:10 So we'll first have to draw the lewis structure.

00:13 In order to do that, find the number of valance electrons.

00:16 So for example, for i have six, we have six fluorines and one iodine.

00:21 Each of these contributes seven valence electrons.

00:24 So seven times seven is 49.

00:25 It is a charge of positive one.

00:27 We have to subtract one.

00:28 And we get 48 total valence electrons.

00:31 Then count the valence electrons in the loose structure to make sure it matches.

00:35 So we have one, two, three, four, five, six of the phalan electrons being used because we have eight around each of the fluorines, and then we're not counting the ones around the iodine twice.

00:48 So we do six times eight, that's 48, so that's correct, and it's going to look like that.

00:52 Iodine can expand its valence.

00:54 And we can take a look at the chart here to see what kind of geometry that is.

00:59 We see that is octahedral.

01:01 So this is octahedral geometry.

01:04 So we move over here, and this is carbon tetrafluoride.

01:09 So if you take a look at that, you will recognize that at tetrahedral because we have four bonds to the central atom...