Honors Biology: Atoms, Bonds, and Water Study Guide

Vocabulary practice flashcards covering atomic structure, chemical bonding, molecular geometry, the properties of water, and pH.

Atomic number

The number of protons in an atom, which equals the number of electrons in a neutral atom.

Mass number

The total number of protons plus neutrons for a single isotope of an element.

Average atomic mass

The decimal value on the periodic table representing the weighted average of an element's isotopes.

Valence electrons

The outer-shell electrons of an atom that participate in chemical bonding.

Electronegativity

A measurement of how strongly an atom attracts shared electrons in a bond.

Cation

A positively charged ion formed when an atom (typically a metal) loses electrons.

Anion

A negatively charged ion formed when an atom (typically a nonmetal) gains electrons.

Ionic bond

The chemical attraction between the resulting opposite charges of a cation and an anion, typically formed between a metal and a nonmetal.

Nonpolar covalent bond

A covalent bond formed by nonmetals sharing electron pairs equally or nearly equally.

Polar covalent bond

A covalent bond characterized by unequal sharing of electron pairs, creating a partially negative ($\delta^-$) end and a partially positive ($\delta^+$) end.

Metallic bonding

A type of bonding typically between metals where valence electrons can move freely through the metal lattice, enabling electrical conductivity.

Bonding pair

A pair of electrons shared between two atoms in a molecule.

Lone pair

An unshared electron pair that remains on a single atom and is represented as two dots in a Lewis structure.

Hydrogen bond

A noncovalent attraction between a $\delta^+$ hydrogen covalently bound to O, N, or F and a lone pair on a neighboring O, N, or F atom.

Cohesion

The attraction between molecules of the same substance, such as water molecules sticking to one another via hydrogen bonding.

Adhesion

The attraction between molecules of different substances, such as water molecules sticking to glass.

Surface tension

A liquid's resistance to increasing its surface area, caused by cohesive forces pulling surface molecules inward.

Capillary action

The process by which adhesion pulls water along a narrow surface while cohesion pulls adjacent water molecules along with it.

High specific heat

The property of water requiring a relatively large amount of heat energy to raise its temperature due to the need to disrupt its hydrogen-bond network.

High heat of vaporization

The property requiring substantial energy for water to evaporate, leading to evaporative cooling as higher-energy molecules escape.

Hydrophilic

A term describing polar substances that interact well with and dissolve easily in water.

Hydrophobic

A term describing nonpolar substances (such as oils) that tend to cluster away from water.

Ion–dipole attraction

An electrostatic attraction between an ion and the partial charge of a polar molecule, such as the $\delta^+$ hydrogen ends of water pointing toward $\text{Cl}^-$.

pH

A logarithmic measure of hydrogen ion concentration calculated as $-\log_{10}[\text{H}^+]$, where each whole unit represents a tenfold change in $[\text{H}^+]$.

Buffer

A substance or chemical system that resists changes in pH by accepting added $\text{H}^+$ or donating $\text{H}^+$ when a base is introduced.