Make three-dimensional drawings of the following molecules, and predict whether each has a dipol

Make three-dimensional drawings of the following molecules,...

Key Concepts

Molecular Geometry

Molecular geometry describes the three-dimensional arrangement of atoms within a molecule. It is crucial for understanding the spatial orientation of bonds, which in turn affects the molecule’s physical properties, including its polarity and dipole moment.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is used to predict a molecule’s geometry based on the repulsion between electron pairs surrounding a central atom. This theory helps in constructing the three-dimensional shapes required to determine whether polar bonds will cancel out or produce a net dipole moment.

Electronegativity

Electronegativity is a measure of the tendency of an atom to attract bonding electrons towards itself. Differences in electronegativity between atoms result in polar bonds that contribute to the overall dipole moment of a molecule, depending on the bond orientation in three-dimensional space.

Dipole Moment

A dipole moment is a vector quantity resulting from the separation of positive and negative charges within a molecule. The overall dipole moment depends on both the magnitude of the individual bond dipoles and their geometric arrangement; symmetric arrangements can lead to cancellation, while asymmetric ones may yield a net dipole moment.

Hybridization

Hybridization involves the mixing of atomic orbitals to form new, hybrid orbitals that shape the bonding framework of a molecule. This concept explains the observed bonding geometries and is essential for predicting the three-dimensional structure and associated properties such as molecular polarity.

Transcript

00:01 They want us to make three -dimensional drawings for each of the following monocles, and then predict whether each is going to have a dipole moment and if it is to show its direction.

00:10 Now, first, recall, anytime we have a double bond, that's going to be a good indicator that these carbons here are going to be sb2 hybridized, which means this is going to be completely planer.

00:23 So just drawing it in the plane of the board will be three -dimensional in this case.

00:27 So we really won't have any issues with this one.

00:35 Now, if we look at the electronegativity chart, so carbon is more electronegative than hydrogen.

00:43 So we would have where these are pulling towards the carbon like this.

00:52 But then notice that this arrow would essentially cancel out with this one, and this arrow cancels out with this one.

01:01 So we would actually expect no dipole for this one, since all of them will just end up canceling each other out.

01:13 All right.

01:14 Now, what about ch2? cl2? well, let's go ahead and draw that first.

01:19 So we have c.

01:21 I'll put the two hydrogens in the plane of the board, and then i'll have one of the chlorines coming out towards us, and the other one facing away.

01:29 So remember, which is means facing towards, a dash line means facing away from.

01:33 From us.

01:34 Well, so we'd have that these two bonds are going to first be going towards the carbon, or these hydrogens are going to be less electronegative than carbon, so it's going to be pulling densely towards the carbon.

01:55 But then the chlorines, if we look over here, are going to be a lot more electronegative than carbon, or not a lot more, but more electronegative.

02:05 So then it's going to pull in this direction like that.

02:11 So if we were to add all these up, notice that the direction kind of, so like going left and right kind of gets canceled out, but we would have words going straight down like this.

02:29 So we would have positive and then going towards the negative like that.

02:34 So like what i mean by them canceling out.

02:37 So like notice these two vectors here are going, towards each other.

02:42 So their directions cancel out, but we could still add up their magnitudes, which essentially would force this to go down and then the same for these chlorines here...

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