General Chemistry Key Vocabulary and Concepts Review

Comprehensive vocabulary flashcards covering atomic structure, periodic properties, matter classification, measurements, and basic laws of chemistry.

Alkali metal

A highly reactive element found in Group 1 of the periodic table, possessing one valence electron.

Alkaline earth metal

A reactive metallic element located in Group 2 of the periodic table, having two valence electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Atom

The fundamental, basic unit of matter that retains the chemical identity and properties of an element.

Atomic mass

The weighted average mass of all naturally occurring isotopes of an element, measured in atomic mass units.

Atomic mass unit (amu)

A standard unit of mass defined as exactly $\frac{1}{12}$ the mass of a carbon-12 atom.

Atomic number (Z)

The number of protons in the nucleus of an atom, which identifies the chemical element.

Avogadro's number

The number of representative particles in one mole of a substance, equal to $6.022 \times 10^{23}$.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Cathode ray

A stream of electrons emitted from the cathode in a vacuum tube, used by J.J. Thomson to discover the electron.

Chemical symbol

A one- or two-letter abbreviation used to represent a specific element on the periodic table.

Dalton's atomic theory

A theory stating that matter is composed of indivisible atoms, atoms of a given element are identical, and chemical reactions involve the combination or rearrangement of atoms.

Electron

A subatomic particle bearing a negative electrical charge, found outside the atomic nucleus.

Group (Family)

A vertical column in the periodic table containing elements with similar chemical properties.

Halogen

A highly reactive nonmetal in Group 17 of the periodic table.

Ion

An atom or group of bonded atoms that carries a net positive or negative electric charge.

Isotope

Atoms of the same element that have the same atomic number but different mass numbers due to differing numbers of neutrons.

Law of conservation of mass

A fundamental chemical principle stating that matter is neither created nor destroyed during a chemical reaction.

Law of definite proportions

A law stating that a given chemical compound always contains its component elements in fixed ratio by mass.

Law of multiple proportions

A law stating that when two elements combine to form more than one compound, the mass ratios of one element combining with a fixed mass of another are simple whole numbers.

Mass number (A)

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

Metalloid

An element with physical and chemical properties intermediate between those of metals and nonmetals.

Metal

An element that is typically shiny, malleable, ductile, and a good conductor of heat and electricity.

Molar mass

The mass in grams of one mole of a substance, expressed in units of $g/mol$.

Mole

The SI base unit for amount of substance, containing exactly $6.022 \times 10^{23}$ elementary entities.

Neutron

A neutral subatomic particle located inside the nucleus of an atom.

Noble gas

An unreactive gas found in Group 18 of the periodic table, characterized by a full valence electron shell.

Nonmetal

An element that generally lacks metallic attributes and is typically a poor conductor of heat and electricity.

Nuclear theory of the atom

Rutherford's atomic model establishing that most of an atom's mass and positive charge is concentrated in a tiny central nucleus.

Nucleus

The small, dense, positively charged region at the center of an atom containing protons and neutrons.

Period

A horizontal row of elements across the periodic table.

Periodic law

The principle stating that when elements are arranged in order of increasing atomic number, their properties recur periodically.

Periodic table

A tabular arrangement of chemical elements organized by atomic number, electron configuration, and recurring chemical properties.

Proton

A subatomic particle bearing a positive charge, located in the atomic nucleus.

Accuracy

A measure of how close a measured value is to the true or accepted value.

Chemical property

A characteristic of a substance that can only be observed or measured during a chemical reaction that changes the substance's identity.

Chemistry

The scientific study of matter, its properties, composition, structure, and the changes it undergoes.

Compound

A pure substance composed of two or more different elements chemically combined in fixed proportions.

Density

An intensive property defined as mass per unit volume, represented mathematically as $d = \frac{m}{V}$.

Element

A pure substance that cannot be broken down into simpler substances by ordinary chemical means.

Extensive property

A property that depends directly on the amount of matter in a given sample.

Heterogeneous mixture

A mixture with a non-uniform composition in which individual components remain visually distinct.

Homogeneous mixture

A mixture with a uniform composition throughout, also referred to as a solution.

Hypothesis

A tentative, testable explanation for a scientific observation or problem.

Intensive property

A property of matter that depends only on the type of matter present, independent of sample size.

International System of Units (SI)

The internationally agreed-upon standard system of metric units used in science.

Law

A concise verbal or mathematical statement that summarizes a universally observed natural phenomenon.

Macroscopic property

A physical or chemical property of matter that can be observed directly with the naked eye.

Mass

A quantitative measure of the amount of matter contained in an object.

Matter

Anything that possesses mass and occupies space.

Microscopic property

A characteristic of matter on the scale of atoms, molecules, or subatomic particles requiring indirect observation.

Mixture

A physical combination of two or more substances in which each substance retains its distinct chemical identity.

Physical property

A characteristic of matter that can be observed or measured without altering the chemical composition of the substance.

Precision

A measure of the closeness or agreement among repeated measurements of the same quantity.

Qualitative

Descriptive measurements or observations that do not involve numerical values.

Quantitative

Data or measurements that are expressed in numerical values and precise units.

Scientific method

A systematic approach to scientific inquiry involving observation, hypothesis formulation, experimentation, and analysis.

Significant figures

The meaningful digits in a measured or calculated quantity that reflect the precision of the measurement.

Substance

A form of matter that has a constant composition and uniform properties throughout.

Theory

A well-tested, comprehensive explanation of natural phenomena based on extensive scientific evidence.

Thomson

The scientist who discovered the electron using cathode rays and proposed the plum pudding model of the atom.

Rutherford

The scientist who discovered the atomic nucleus through the gold foil experiment and established the nuclear theory of the atom.

Dimensional analysis

A problem-solving method that uses conversion factors to convert units from one form to another.