Chemical Reactions and Bonds - Chapter 2, Section 3

Vocabulary flashcards covering key terms from the notes on chemical reactions and bonds.

Molecule

A group of two or more atoms bonded together; may be an element or compound, but a molecule is not necessarily a compound.

Compound

A substance formed when two or more different elements are chemically bonded together.

O2

A diatomic molecule consisting of two oxygen atoms; a molecule but not a compound.

CO2

A molecule and a compound consisting of one carbon atom and two oxygen atoms.

CH4

A molecule and a compound consisting of one carbon atom bonded to four hydrogen atoms.

NaCl

A compound formed from sodium and chloride ions bonded ionically.

Chemical reaction

A process in which bonds are formed, broken, or rearranged, involving electrons; rate increases with higher temperature, higher reactant concentration, or a catalyst.

Reactant

Substances present at the start of a chemical reaction; written on the left side of a chemical equation.

Product

Substances formed by a chemical reaction; written on the right side of a chemical equation.

Catalyst

A substance that speeds a reaction without being consumed; often an enzyme in biology.

Enzyme

A biological catalyst that accelerates a specific chemical reaction.

Electron

A subatomic particle involved in chemical reactions; negatively charged; participates in bond formation and breaking.

Chemical equation

A symbolic representation of a chemical reaction using molecular formulas, with reactants on the left and products on the right.

Molecular formula

The set and number of atoms in a molecule, e.g., H2O, CO2.

Synthesis

A reaction where A and B combine to form AB.

Decomposition

A reaction where AB breaks into A and B.

Exchange reaction

A reaction where AB + CD → AC + BD; parts swap partners.

Reversible reaction

A reaction that can proceed in both forward and reverse directions, shown with a reversible arrow (⇌).

Bond

A force holding atoms together by storing chemical potential energy.

Ionic bond

A bond formed by transfer of electrons, creating ions that are held together by electrostatic attraction.

Ion

An atom or molecule with a net electric charge due to gain or loss of electrons.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Electrolyte

A substance that produces ions in solution; in biology, ions like Na+ and Cl− are electrolytes.

Covalent bond

A bond formed by sharing electrons between atoms.

Single bond

A covalent bond where one pair of electrons is shared.

Double bond

A covalent bond where two pairs of electrons are shared.

Nonpolar covalent bond

A covalent bond in which electrons are shared equally; example O2.

Polar covalent bond

A covalent bond in which electrons are shared unequally, producing partial charges; example H2O.

Electronegativity

The tendency of an atom to attract electrons in a bond.

Hydrogen bond

A weak attraction between partial positive and partial negative charges in polar molecules; important in water, DNA, and protein structure; easily broken and reformed.

Lewis dot structure

A diagram showing valence electrons around atoms; used to predict gain/loss/share of electrons; covalent bonds are shown as shared electron pairs.

Valence electron

Electrons in the outermost shell involved in bonding.