Regents Chemistry – August 2024 Key Vocabulary

Sixty vocabulary flashcards covering major concepts, terms, and principles appearing in the August 2024 Regents Chemistry examination.

Atomic Mass Unit (amu)

A mass exactly 1⁄12 of a carbon-12 atom; roughly the mass of one proton or one neutron.

Proton

Positively charged nuclear particle with a mass of about 1 amu.

Neutron

Neutral nuclear particle with a mass of about 1 amu.

Electron

Negatively charged particle with negligible mass found in orbitals around the nucleus.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Excited State

Condition in which an atom’s electrons occupy higher-energy levels after absorbing energy.

Ground State

Lowest-energy electron configuration of an atom.

Allotrope

Different structural forms of the same element in the same phase (e.g., O₂ vs O₃) with distinct properties.

Compound

Pure substance composed of two or more different elements chemically combined in fixed ratios.

Conservation of Charge

Total electric charge remains constant throughout any chemical reaction.

Metallic Bond

Attraction between positive metal ions and a ‘sea’ of mobile valence electrons.

Valence Electron

Electron in the outermost shell that participates in chemical bonding.

Electronegativity

Measure of an atom’s attraction for shared electrons in a bond.

First Ionization Energy

Energy required to remove the most loosely held electron from a gaseous atom in its ground state.

Mixture

Physical combination of substances that retain their individual properties and can vary in composition.

Substance

Matter with uniform, definite composition; an element or a compound.

Distillation

Separation technique based on differences in boiling points of mixture components.

Boiling Point

Temperature at which a liquid’s vapor pressure equals external pressure, causing it to vaporize.

Freezing Point

Temperature at which a liquid becomes a solid; 0 °C for water at 1 atm.

Thermal Energy

Total kinetic energy of all particles in a substance; relates to temperature.

Kinetic Energy

Energy a particle possesses due to its motion.

Ideal Gas

Hypothetical gas whose particles have no volume or attractions and obey all gas laws perfectly.

Kinetic Molecular Theory

Model describing ideal gas behavior in terms of constant, random motion and elastic collisions.

Collision Theory

Concept that reactions occur when particles collide with correct orientation and sufficient energy.

Chemical Equilibrium

Dynamic state where forward and reverse reaction rates are equal and concentrations remain constant.

Activation Energy

Minimum energy needed for reacting particles to form an activated complex and react.

Catalyst

Substance that speeds a reaction by providing a lower-energy pathway and is regenerated unchanged.

Reduction

Process involving the gain of electrons by a species.

Oxidation

Process involving the loss of electrons by a species.

Alpha Particle

Helium-4 nucleus (2 p, 2 n) emitted in radioactive decay; low penetration.

Beta Particle

High-speed electron (β⁻) or positron (β⁺) emitted from a nucleus; moderate penetration.

Gamma Radiation

High-energy electromagnetic radiation from a nucleus; highest penetrating power.

Nuclear Fission

Splitting of a heavy nucleus into lighter nuclei, releasing large amounts of energy.

Percent Error

|(experimental – accepted) ÷ accepted| × 100 % to express accuracy of a measurement.

Single Replacement Reaction

Reaction where one element replaces another element in a compound.

Le Chatelier’s Principle

A system at equilibrium shifts to counteract an applied stress.

Unsaturated Hydrocarbon

Organic molecule containing C=C or C≡C bonds (alkenes or alkynes).

Fermentation

Anaerobic conversion of glucose to ethanol and CO₂ by yeast.

Combustion Reaction

Exothermic reaction of a substance with O₂ producing oxides and releasing heat/light.

Arrhenius Acid

Substance that produces H⁺/H₃O⁺ ions in aqueous solution.

Arrhenius Base

Substance that produces OH⁻ ions in aqueous solution.

Electrolyte

Substance whose aqueous or molten form conducts electricity due to mobile ions.

Significant Figures

Digits that convey precision in a measured value, including one uncertain digit.

Mole Ratio

Proportional relationship between amounts of reactants/products in a balanced equation.

Electrolysis

Nonspontaneous redox process driven by external electrical energy.

Voltaic Cell

Electrochemical cell where a spontaneous redox reaction generates electrical energy.

Brønsted-Lowry Acid

Proton (H⁺) donor in a reaction.

Brønsted-Lowry Base

Proton (H⁺) acceptor in a reaction.

Lewis Electron-Dot Diagram

Drawing that shows valence electrons as dots around atoms or within bonds.

Metalloid

Element with both metallic and nonmetallic properties; found along the staircase on the periodic table.

Precipitation Reaction

Reaction that forms an insoluble solid when two aqueous solutions are mixed.

Gram-Formula Mass (Molar Mass)

Mass of one mole of a substance calculated from atomic masses.

Vapor Pressure

Pressure exerted by a vapor in equilibrium with its liquid at a given temperature.

Intermolecular Forces

Attractive forces between molecules, including hydrogen bonding, dipole-dipole, and dispersion forces.

Polar Molecule

Molecule with an uneven charge distribution due to asymmetry and electronegativity differences.

Endothermic Process

Process that absorbs heat, causing the surroundings to cool.

Saturated Solution

Solution holding the maximum amount of solute at a given temperature.

Parts per Million (ppm)

Concentration unit equal to milligrams of solute per liter of solution for dilute aqueous systems.

Half-Life

Time required for half the nuclei in a radioactive sample to decay.

Neutron-to-Proton Ratio

Comparison of neutrons to protons in a nucleus; key factor in nuclear stability.