Chemistry of Life - Unit 1 APBio: Bonding & Polarity

Vocabulary flashcards covering bonding types, electronegativity, polarity concepts, and their biological relevance.

Bond

A lasting attraction between atoms that lowers potential energy and stabilizes matter; can be ionic or covalent.

Bond length

The average distance between the nuclei of two bonded atoms (internuclear distance); example: H–H around 74 pm.

Ionic bond

A bond formed by transfer of electrons from one atom to another, creating oppositely charged ions held together by electrostatic attraction.

Covalent bond

A bond formed by sharing one or more pairs of electrons between atoms, forming a molecule.

Electronegativity

The tendency of an atom to attract electrons in a chemical bond; measured on scales like the Pauling scale.

Polar covalent bond

A covalent bond with unequal sharing of electrons due to different electronegativities, producing partial charges.

Nonpolar covalent bond

A covalent bond with approximately equal sharing of electrons (electronegativity difference is small).

Dipole

A molecule or part of a molecule with a positive and a negative end due to unequal electron distribution (water is a dipole).

Polar molecule

A molecule with a net dipole moment caused by polar bonds and a non-symmetric shape.

Nonpolar molecule

A molecule with no net dipole moment because its bonds are nonpolar or arranged symmetrically (e.g., Cl₂).

CHONPS

The six essential biological elements: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), sulfur (S).

Atomic number

The number of protons in an atom’s nucleus; defines the element.

Mass number

The total number of protons and neutrons in a given isotope.

Atomic mass

The average mass of an element’s atoms, accounting for the relative abundance of its isotopes.

Pauling scale

A scale for electronegativity introduced by Linus Pauling to compare how strongly atoms attract electrons.

Bond vs. molecular polarity

Bond polarity depends on electronegativity difference; molecular polarity also depends on the molecule’s shape.

Partial charges

Small, fractional charges (δ+ and δ−) that arise from unequal electron sharing in bonds.

Polarity in biology

Polar molecules interact with charged or polar surroundings (like water in cells), influencing membranes, proteins, and macromolecular structure.