General Chemistry

Cards · 57

Mole

The amount of a substance that contains exactly 6.022 x 10^23 elementary entities such as atoms, molecules, or ions.

Avogadro's Number

6.022 x 10^23, representing the number of constituent particles per mole of any chemical substance.

Molar Mass

The mass of one mole of a chemical element or compound, expressed in grams per mole (g/mol).

Isotopes

Atoms of the same element with identical numbers of protons but different numbers of neutrons, resulting in different mass numbers.

Atomic Number (Z)

The total number of protons found in the nucleus of an atom, uniquely defining the chemical element.

Mass Number (A)

The total number of protons and neutrons combined in the nucleus of an atom.

Aufbau Principle

Electrons fill lower-energy atomic orbitals before occupying higher-energy ones.

Pauli Exclusion Principle

No two electrons in an atom can have identical values for all four quantum numbers; an orbital holds at most two opposite-spin electrons.

Hund's Rule

Electrons occupy degenerate orbitals singly and with parallel spins before doubly occupying any orbital.

Valence Electrons

Electrons in the outermost principal energy level that participate in chemical bonding and determine chemical reactivity.

Electronegativity

The relative ability of an atom in a chemical compound to attract shared electrons to itself.

Ionization Energy

The energy required to remove the most loosely held electron from an isolated gaseous atom in its ground state.

Electron Affinity

The energy change that occurs when an electron is added to a neutral gaseous atom to form an anion.

Atomic Radius Trend

Increases down a group due to added electron shells and decreases across a period due to increasing effective nuclear charge.

Ionic Bond

An electrostatic attraction between oppositely charged ions formed by the transfer of one or more valence electrons.

Covalent Bond

A chemical bond formed when two atoms share one or more pairs of valence electrons.

Polar Covalent Bond

A covalent bond where electrons are shared unequally between atoms with different electronegativities, creating a dipole.

Octet Rule

The tendency of main-group atoms to gain, lose, or share electrons until they achieve an electron configuration with eight valence electrons.

Lewis Structure

A two-dimensional diagram that shows bonds between atoms of a molecule and the lone pairs of electrons that exist.

Resonance Structures

Two or more valid Lewis structures for a single molecule that differ only in the placement of electrons, not atoms.

VSEPR Theory

Predicts three-dimensional molecular geometries based on minimizing electrostatic repulsion between electron pairs around a central atom.

Dipole Moment

A quantitative measure of the polarity of a chemical bond or molecule, calculated as the product of charge and separation distance.

London Dispersion Forces

Weak, temporary intermolecular attractions caused by momentary fluctuations in electron density creating instantaneous dipoles.

Hydrogen Bonding

A strong dipole-dipole attraction occurring when hydrogen covalently bonds to a highly electronegative atom (N, O, or F) and interacts with another.

Ideal Gas Law

The equation of state PV = nRT, relating pressure, volume, moles, and temperature of an ideal gas.

Boyle's Law

The pressure of an ideal gas is inversely proportional to its volume at constant temperature and mole quantity (P1V1 = P2V2).

Charles's Law

The volume of an ideal gas is directly proportional to its absolute temperature at constant pressure (V1/T1 = V2/T2).

Dalton's Law of Partial Pressures

The total pressure exerted by a mixture of non-reacting gases equals the sum of the partial pressures of each individual gas.

Vapor Pressure

The pressure exerted by a vapor in dynamic equilibrium with its liquid or solid phase at a given temperature in a closed system.

Molarity (M)

A concentration unit defined as the number of moles of solute dissolved per liter of solution.

Molality (m)

A concentration unit defined as the number of moles of solute per kilogram of solvent, independent of temperature.

Colligative Properties

Physical properties of solutions that depend solely on the concentration of solute particles, not their chemical identity.

Limiting Reactant

The reactant that is completely consumed first in a chemical reaction, determining the maximum theoretical yield of product.

Percent Yield

The ratio of the actual experimental yield of product to the theoretical calculated yield, expressed as a percentage.

Endothermic Reaction

A process that absorbs thermal energy from its surroundings, characterized by a positive change in enthalpy (ΔH > 0).

Exothermic Reaction

A process that releases thermal energy to its surroundings, characterized by a negative change in enthalpy (ΔH < 0).

Hess's Law

The total enthalpy change for a reaction is equal to the sum of the enthalpy changes for the individual reaction steps.

Entropy (S)

A thermodynamic measure of the dispersal of matter and energy, or the degree of disorder within a chemical system.

Gibbs Free Energy (ΔG)

A thermodynamic quantity (ΔG = ΔH - TΔS) that determines the spontaneity of a process at constant temperature and pressure.

Activation Energy (Ea)

The minimum kinetic energy that colliding reactant molecules must possess for a chemical reaction to occur.

Catalyst

A substance that accelerates a chemical reaction by providing an alternative pathway with a lower activation energy without being consumed.

Rate Law

An equation relating reaction rate to the concentrations of reactants raised to experimentally determined powers (reaction orders).

Dynamic Equilibrium

A state in a reversible reaction where the rates of forward and reverse reactions are equal, keeping reactant and product concentrations constant.

Equilibrium Constant (K)

The ratio of product concentrations to reactant concentrations at equilibrium, each raised to their stoichiometric coefficients.

Le Chatelier's Principle

If an external stress is applied to a system at equilibrium, the system shifts in a direction that counteracts that disturbance.

Arrhenius Acid and Base

An acid increases hydrogen ion (H+) concentration in water; a base increases hydroxide ion (OH-) concentration in water.

Brønsted-Lowry Acid and Base

An acid acts as a proton (H+) donor, while a base acts as a proton (H+) acceptor in a reaction.

Lewis Acid and Base

An acid is an electron-pair acceptor; a base is an electron-pair donor.

pH

The negative logarithm (base 10) of the hydronium ion concentration, measuring the acidity or basicity of an aqueous solution.

Buffer Solution

A solution containing a weak acid and its conjugate base that resists drastic pH changes upon the addition of small amounts of acid or base.

Solubility Product Constant (Ksp)

An equilibrium constant representing the extent to which a sparingly soluble ionic solid dissolves in aqueous solution.

Oxidation

The chemical process involving the loss of electrons by an atom, ion, or molecule, leading to an increased oxidation state.

Reduction

The chemical process involving the gain of electrons by an atom, ion, or molecule, leading to a decreased oxidation state.

Oxidizing Agent

A substance that causes oxidation by accepting electrons, undergoing reduction itself in the process.

Galvanic (Voltaic) Cell

An electrochemical cell that generates electrical energy from a spontaneous chemical redox reaction.

Electrolytic Cell

An electrochemical cell that uses an external electrical power source to drive a non-spontaneous chemical redox reaction.

Standard Reduction Potential (E°)

The voltage associated with a reduction half-reaction at standard conditions relative to the standard hydrogen electrode.