Chapter 2 Notes: Chemical Bonds — Electronegativity, Bond Types, and Intermolecular Forces

Flashcards covering electronegativity, bond types (ionic, covalent, polar/nonpolar), intramolecular vs intermolecular forces, hydrogen bonds, van der Waals, hydrophobic interactions, shape vs. function, and basic bonding concepts.

What is electronegativity?

A measure of the tendency of an atom to attract a bonding pair of electrons.

What happens when two atoms of equal electronegativity bond together?

They form a nonpolar covalent bond with electrons shared equally.

If molecule B is slightly more electronegative than A, what type of bond forms?

A polar covalent bond, with electrons pulled toward B.

If B is much more electronegative than A, what happens?

An ionic bond forms; electrons are transferred, producing ions.

What electronegativity difference yields a nonpolar covalent bond?

0 to about 0.4.

What electronegativity difference yields a polar covalent bond?

About 0.4 to 1.7.

What electronegativity difference yields ionic character?

Greater than about 1.7.

What are intermolecular forces?

Forces that occur between molecules; include van der Waals and hydrogen bonds; typically weaker than intramolecular bonds.

What is a hydrogen bond?

A type of intermolecular force where a hydrogen atom covalently bonded to a highly electronegative atom (like O or N) is attracted to another electronegative atom in a nearby molecule.

What are van der Waals forces?

Weak intermolecular attractions arising from transient dipoles due to electron movement.

What are hydrophobic interactions?

Nonpolar portions of molecules clump together in water to avoid contact with water.

What is an ionic bond?

A bond formed by transfer of electrons from one atom to another, creating ions that attract.

What is a covalent bond?

A bond formed by sharing electrons between atoms; can be polar or nonpolar.

What is a nonpolar covalent bond?

A covalent bond with nearly equal sharing of electrons due to a very small or zero electronegativity difference.

What is a polar covalent bond?

A covalent bond with unequal sharing of electrons due to a moderate electronegativity difference.

Give an example of an ionic bond.

Sodium chloride (NaCl), formed by the attraction between Na+ and Cl− ions.

What is a disulfide bridge?

A covalent bond between sulfur atoms in proteins that helps stabilize structure.

Why is molecular shape important in biology?

Shape determines how biological molecules recognize and interact with each other, affecting function.

What determines a molecule's shape?

The positions of an atom's orbitals (and their electrons).

What are valence electrons?

Electrons in the outermost electron shell involved in bonding.

What is the valence shell?

The outermost electron shell of an atom.

Why do atoms form chemical bonds?

To become more stable by filling or emptying their valence shells.

How many electrons are shared in a single covalent bond?

Two electrons are shared.

How many electrons are shared in a double covalent bond?

Four electrons are shared.