Which of the molecules in Exercise 122 have net dipole moments (are polar)?

Name: Problem 126, Chapter 8: Chemistry
Uploaded: 2019-08-22T20:21:39-08:00
Duration: 5 min 46 s
Channel: Lena Jake
Description: Which of the molecules in Exercise 122 have net dipole moments (are polar)?

Which of the molecules in Exercise 122 have net dipole...

Key Concepts

Vector Addition of Dipole Moments

Since dipole moments are vector quantities, their overall effect in a molecule is determined by the vector sum of the individual bond dipoles. This means that the direction and magnitude of each bond dipole influence whether they cancel out or add up to create a net dipole moment.

Molecular Geometry and Symmetry

The three-dimensional arrangement of atoms in a molecule (its molecular geometry) plays a crucial role in determining polarity. Even when bonds are polar, a symmetric arrangement can lead to a cancellation of individual bond dipoles, resulting in a nonpolar molecule. Conversely, asymmetry can result in a net dipole moment.

Electronegativity

Electronegativity is the measure of an atom's ability to attract shared electrons in a bond. Differences in electronegativity between atoms in a bond can lead to polar bonds, which contribute to the overall dipole moment of a molecule.

Molecular Polarity

Molecular polarity refers to the distribution of electrical charge across a molecule, resulting in a net dipole moment when the centers of positive and negative charges do not coincide. It is determined by both the polarity of individual bonds and the overall molecular geometry.

Transcript

00:02 So in this video, we're going to go over question 126 from chapter 8, which asks us which of the molecules from exercise 122 have net dipole moments.

00:12 So in part a of exercise 122, we had the molecule icl5.

00:19 So our iodine is going to bring seven valence electrons, and then each of our five chlorine atoms is going to bring seven valence electrons.

00:26 So that's a total of 42 electrons.

00:28 So let's draw lewish structure using those 42 electrons.

00:33 So if iodine is my central atom, i draw five chlorine atoms surrounding it, and i can fill in the octets on those chlorine atoms, which will use up 8 times 5 electrons.

00:50 So 8 times 5 is 40, i'm going to use up 40 electrons, and i had 42 to start with.

00:55 So that means i have one pair of electrons left over, which i'm going to put on my central iodine atom.

01:00 So the general structure for this lewis structure would be ax5e, meaning i have six things around my central atom.

01:13 Five of them are bonded atoms, x, and one of them is an electron pair, e.

01:19 So anytime i have a structure that is ax5e, it is a square pyramid.

01:26 It's a variation on the octahedral geometry that we call a square pyramid.

01:34 So let's take a look at what this looks like.

01:38 So it looks like an octahedral structure, except one of the points on the octahedral structure, is a lone pair of electrons.

01:46 So you have the square of corin atoms in plain with the iodine atom, and then above the iodine atom, you have a chlorine atom bonded, and below it you have your pair of electrons.

01:56 So the fact that we have this lone pair of electrons here, and we have a chlorine atom above, but not a chlorine atom below, means that we have a net dipole moment.

02:08 We have nothing countering that icl bond below the iodine atom.

02:16 We only have one pointing upwards.

02:19 So we do have a net dipole moment.

02:21 This molecule is polar because of the asymmetry of the molecule.

02:27 So in b, we had xe -cl -4.

02:30 So we know that xenon is going to bring eight valence electrons, and each of the four coring atoms will bring seven valence electrons, so that's a total of 36 electrons.

02:41 So i can draw my central xenon atom with four chlorine atoms bonded to it, and then if i fill in the octet on my corine atoms on all four of them, then i use up eight times four electrons, which is 32 electrons.

02:59 So that leaves me four electrons remaining, which i'm going to put on my xenon central atom...

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