C-202 Chemistry Semester Exam Study Guide

Vocabulary flashcards covering lab safety, atomic structure, periodic trends, chemical bonding, nomenclature, chemical reactions, and stoichiometry from the Spring 2025 Study Guide.

Octet Rule

The principle stating that ions tend to acquire $8$ valence electrons to become stable.

Valence Electrons

Electrons located in the outermost energy level of an atom.

Electronegativity

The ability of an atom to attract electrons.

Isotope

Atoms of the same element that have a different number of neutrons.

Ion

A charged particle formed when an atom gains or loses electrons.

Cation

A positively charged ion ($+$) formed by losing electrons.

Anion

A negatively charged ion ($-$) formed by gaining electrons.

Lewis Dot Diagram

A visual model that shows the number of valence electrons around the symbol of the element.

Atomic Radius

The size of an atom; it decreases across a period and increases down a group.

Ionization Energy

The energy required to remove an electron from an atom.

Effective Nuclear Charge ($Z_{eff}$)

The net positive charge experienced by valence electrons, calculated as $Z_{eff} = Z - S$.

Compound

Two or more elements that are chemically combined.

Molecule

A covalently bonded compound where electrons are shared.

Formula Unit

The simplest ratio of ions in an ionic compound.

Covalent Bond

A chemical bond where electrons are shared between nonmetal atoms.

Ionic Bond

An electrostatic force where opposite charges hold substances together, generally between a metal and a nonmetal.

Sigma Bond ($\sigma$)

A single covalent bond where an electron pair is shared by direct overlap of orbitals.

Pi Bond ($\pi$)

Bonds found in double or triple covalent bonds where parallel orbitals overlap to share electrons.

Diatomic Elements

The seven elements that exist as pairs in nature: $H_2$, $N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, and $I_2$.

Law of Conservation of Matter

States that during a chemical reaction, matter cannot be created or destroyed, only change form.

Chemical Reaction

A process where bonds break and atoms rearrange to form new substances.

Reactants

The starting substances in a chemical reaction, located on the left side of the arrow.

Products

The substances formed during a chemical reaction, located on the right side of the arrow.

Activation Energy

The minimum amount of energy needed to start a chemical reaction.

Precipitate

A solid produced from a reaction of two or more aqueous solutions.

Catalyst

A substance that speeds up a chemical reaction without being consumed or used up.

Endothermic Reaction

A reaction that absorbs heat, characterized by products having more energy than the reactants.

Exothermic Reaction

A reaction that releases heat into its surroundings.

Synthesis Reaction

A reaction where two or more reactants combine to form a single product.

Decomposition Reaction

A reaction where a single reactant breaks down into two or more products.

Single-Displacement Reaction

A reaction where one element replaces another element in a compound.

Double-Displacement Reaction

A reaction where two compounds exchange ions to form two new compounds.

Combustion Reaction

A reaction where a substance reacts with oxygen ($O_2$), often producing $CO_2$ and $H_2O$.

Avogadro's Number

The number of particles in one mole of a substance, equal to $6.02 \times 10^{23}$.

Molar Mass

The mass in grams of one mole of a substance ($g/mol$).

Percent Composition

The percent by mass of each element in a compound, calculated as $(\frac{\text{mass of element}}{\text{mass of compound}}) \times 100$.

Limiting Reactant

The reactant that is totally consumed first in a chemical reaction, limiting the amount of product formed.

Theoretical Yield

The maximum amount of product that can be produced from a given amount of reactant according to stoichiometric calculations.

Actual Yield

The amount of product that is physically produced and measured during an experiment.

Percent Yield

The ratio of actual yield to theoretical yield expressed as a percentage: $(\frac{\text{actual}}{\text{theoretical}}) \times 100$.