Predict the shapes of the following molecules, and then...

Predict the shapes of the following molecules, and then predict which would have resultant dipolemoments: (a) $\mathrm{SO}_{2} ;$ (b) $\mathrm{NH}_{3} ;$ (c) $\mathrm{H}_{2} \mathrm{S} ;$ (d) $\mathrm{C}_{2} \mathrm{H}_{4} ;$ (e) $\mathrm{SF}_{6}$; (f) $\mathrm{CH}_{2} \mathrm{Cl}_{2}$.

Key Concepts

Molecular Symmetry

Molecular symmetry concerns the balanced arrangement of atoms within a molecule. High symmetry in a molecule can lead to cancellation of individual bond dipole moments, resulting in a nonpolar molecule despite the presence of polar bonds. Conversely, asymmetrical arrangements can result in a net dipole moment, making the molecule polar.

Dipole Moment

A dipole moment is a measure of the overall polarity of a molecule, resulting from the vector sum of individual bond dipoles. Molecules with asymmetrical charge distributions typically exhibit a net dipole moment, which affects interactions such as solubility, boiling point, and reactivity.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is influenced by factors such as electron pair repulsion and the types of bonds present, and it plays a critical role in determining the overall shape of the molecule, which affects its chemical and physical properties.

Bond Polarity

Bond polarity arises from the difference in electronegativity between two bonded atoms. When electrons are shared unequally, a polar bond is created with a partial positive end and a partial negative end. The degree of bond polarity influences the distribution of charge within the molecule.

VSEPR Theory

The Valence Shell Electron Pair Repulsion (VSEPR) Theory is a model used to predict the geometry of a molecule based on the repulsions between electron pairs around a central atom. By considering both bonding pairs and lone pairs, VSEPR helps determine the spatial arrangement that minimizes electron pair repulsion, leading to various molecular shapes such as linear, trigonal planar, tetrahedral, and others.

Transcript

00:01 Okay, so we're asked about the shapes of the following molecules.

00:04 The first one is so2.

00:08 So if you look at the periodic table, sulfur has six valence electrons, so one, two.

00:15 And then a bond is two electrons share between two atoms.

00:20 Oxygen also has six valence electrons, so one, two, three, four.

00:24 It has two bonds, so in total six.

00:29 And it's shaped like this because the electrons on sulfur repel the electrons.

00:33 All in oxygen and it's more favorable as opposed to a straight line and this shape is bent the next one is nh3 so again it's looking at the period table it has five valence electrons so if three bonds it's three electrons plus the two up top and it's shaped like this for the same reason that the electrons repel the hydrogen and this is going to be trigonal pyramidal pyramidal case the next one is um um um um um um um um sh2 and this is going to be a similar shape to the the so2 so we're going to sulfur with the only difference here is that sulfur is going to have more electrons that aren't in bonds so four five and six the same shape for the same reasons and then the next one is ethane c2 h4 so we can draw it like this we have an alkeen and then carbon can form four bonds so we have two hydrogens here same on the other side so and this is going to be trigonal planar the next one is sf6 so can sulfur forming or six valence electrons so one two three four five and six actually you know let me redraw that okay so fluorine is a halogen, and they have seven valence electrons.

03:21 So we draw it out.

03:38 The shape is going to be octahedral.

03:44 So octa, meaning 8, and f.

03:51 We have ch2, cl2...

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