Polar vs. nonpolar bonds/molecules

[luludaly2B]

Can someone help me with this question on the sapling homework?
I am still having trouble understanding what it means for a molecule/bond to be polar. I thought, because there are two molecules with the same electronegativity on either side of the central molecule, the bonds are nonpolar. Is that incorrect? Does anyone have any tips on how to understand polarity better? Thank you!

[Mohamed Mido]

That is correct only if the molecule has a linear shape because the dipole moments would cancel out. If there are lone pairs on the central atom, there will be repulsion between both Lone Pair-Lone Pair and Lone Pair-Bonding Pair, so the shape would be bent and therefore the dipole moments won't cancel out and the molecule would be more polar.

[Sabina House 2A]

If there are two of the same atom on each side of a central atom (with no lone pairs on the central atom), the overall molecule would be nonpolar. However, the individual bonds inside the molecule are still polar bonds because they are between different atoms, but because the molecule is linear, it would be a nonpolar molecule overall. I hope this helps!

[Sahaj Patel Lec3DisK]

Polar bonds are when there is a strong electronegative difference between the central atom and the other atom(s) in the bond. Nonpolar bonds result when there is a low to none electronegativity difference between the central atom and the other atom(s) in the bond. However, if there are polar interactions in a molecule, but those interactions cancel each other out (like in carbon dioxide), then the molecule will be nonpolar. The easiest way to do this is by drawing an arrow from the least electronegative atom to the most. When there are several arrows, it the arrows run in opposite directions the molecule is nonpolar. If the arrows run in the same direction, it is polar. Hope this helps!

[Shivani Kapur 2J]

Drawing the molecule out really helps visualize if it's nonpolar or polar. Since the arrows both point outward from the Carbon to the Oxygens, the dipole moments cancel out and therefore the molecule in nonpolar.

[VincentLe_3A]

The polarity of a molecule depends on both its shape and dipole moments between the individual atoms. The most methodical way of finding polarity would be to draw out the lewis structure and figure out the VSEPR shape. From there, draw out the arrows which represent the dipole moments in which the electron density is greater towards the more electronegative atom. You would then compare the dipole moments and see if any cancel out throughout the molecule. If all the dipole moments cancel, then the molecule would be considered non polar. It is also important to consider shape, as the presence of lone pairs of electrons on the central atom will result in polar characteristics.

[Malakai Espinosa 3E]

In my opinion, I think visualising the shape of a molecule best helps me understand polarity. It's like a game of tug of war. If both sides are equal in strength, the rope won't move(nonpolar), however, if one side is stronger than the other, than the rope will gravitate towards that side(polar). Also, tug of war doesn't work if the two sides are not opposite of each other(this helps visualize what their relative positions need to be in order to cancel out).

[emmaferry2D]

you have to keep into account the shape of the compound in questions. For example the lewis structure of a tetrahedral molecule with 4 atoms bonded that are not the same may look as if the dipole moments cancel out. However, when you take into account the tetrahedral molecular structure of the molecule, the dipole moments do not cancel out.

[Annette Fishman]

A bond is polar because two atoms have different electronegativities. However, when these two atoms (or more) are symmetric and have zero lone pairs, this indicates that this molecule has linear geometry. The bonds are symmetric, so their dipoles cancel out. Thus, the molecule is nonpolar.
On the other hand, in the case where dipoles do not cancel out, the molecule is polar. The asymmetric arrangement of the lone pairs further contributes to dipoles as well. This is seen in H2O, which has bent geometry. Similarly to the first, if two atoms have different electronegative, the bond will always be polar.