Unit 3: Intermolecular Forces and Properties

What are intermolecular forces

Attractions between atoms, ions, or molecules that influence physical properties

What are the four different types of IMFs? (weakest to strongest)

London dispersion forces, dipole-dipole forces, hydrogen bonds, ion-dipole forces

T/F: London dispersion forces only occur in nonpolar substances.

False: London dispersion forces occur in all substances, polar and nonpolar.

What is polarizability?

The ability of an atom to form a temporary or induced dipole

What are the full charges of ions?

multiples of the charge of one electron (1.16e-19 C)

Electrons are in shells and orbitals that are ______ ________ in ______.

always changing, position

Why are electrons usually evenly distributed in shells and orbitals?

To minimize repulsions

What happens when the electron cloud “wobbles”?

It can create temporary dipoles, inducing polarization in nearby atoms.

Partial charges _ full ionic charges

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What is an induced dipole?

A temporary shift in electron density in an atom or molecule that occurs due to the influence of another substance; results in the formation of a dipole moment in an otherwise nonpolar molecule.

Why do larger and thinner molecules have stronger LDFs?

Larger and thinner molecules have greater London dispersion forces (LDFs) because their elongated shapes and greater amount of electrons allow for more surface area contact, leading to increased polarizability and stronger temporary dipoles.

LDFs determine the properties of ____ and _____.

single atoms and nonpolar molecules

What allows for permanent dipoles in molecular structures?

A significant electronegativity difference between bonded atoms + suitable molecular shape (non-symmetrical)

Dipole-dipole interactions are stronger than LDS in _______ molecules.

equivalent; similar # of similar sized atoms with identical # of electrons

What differentiates hydrogen bonds from regular dipole-dipole forces?

Hydrogen bonds occur when hydrogen is covalently bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine, resulting in a stronger interaction compared to regular dipole-dipole forces.

How do hydrogen bonds become intermolecular?

Hydrogen bonds become intermolecular when the hydrogen atom of one molecule interacts with the electronegative atom of another molecule, creating a strong attraction between them.