Unit 9: Polarity and IMF

Flashcards covering the definitions of polar and nonpolar bonds and molecules, including rules for molecular symmetry and specific chemical examples.

Polar bond

Bonds where the electrons are shared unequally between atoms, where the more electronegative atom pulls the electrons closer to itself.

Nonpolar bond

Bonds where electrons are shared equally between two atoms that have the same electronegativity value.

Electronegativity pull (in HF)

In an $HF$ molecule, shared electrons are held closer to fluorine because it is more electronegative, creating a $-\delta$ and $+\delta$ polarity.

Polar molecule (General Rule)

Molecules that have different atoms around a central atom.

Nonpolar molecule (General Rule)

Molecules that have the same atoms around a central atom, resulting in electrons being shared equally.

$$H_2$$

An example of a nonpolar molecule because both atoms have the same electronegativity value.

$$CCl_4$$

An example of a nonpolar molecule because all atoms surrounding the carbon central atom are the same ($Cl$).

$CO_2$ vs. $COS$

$CO_2$ is nonpolar because the atoms around carbon are the same, whereas $COS$ is polar because the atoms around carbon ($O$ and $S$) are different.

Unshared electrons

In molecules like $H_2O$ and $NH_3$, these should be pictured as a "different atom" when determining if a molecule is polar or nonpolar.

$$CH_4$$

A nonpolar molecule where all four atoms ($H$) surrounding the central carbon are the same.

$$CH_3Cl$$

A polar molecule because there are different atoms ($H$ and $Cl$) surrounding the central carbon atom.