General Chemistry I – Matter, Atomic Structure & Electronic Configuration

A comprehensive set of 200 vocabulary flashcards covering key terms and definitions from General Chemistry I topics: properties of matter, separation techniques, states of matter, laws of chemical combinations, atomic models, subatomic particles, quantum mechanics, electron configuration, and related concepts.

Matter

Anything that has mass and occupies space (has volume).

Mass

A measure of the amount of matter in a substance; SI unit kilogram (kg).

Volume

The amount of space a substance occupies; SI unit cubic metre (m³).

Physical Property

Characteristic observed without changing a substance’s composition (e.g., colour, density).

Chemical Property

Characteristic observed when a substance is converted into a different substance (e.g., flammability).

Intensive Property

Property independent of the amount of substance, useful for identification (e.g., density).

Extensive Property

Property that depends on the amount of substance present (e.g., mass, volume).

Texture

The physical appearance or surface feel of matter.

Brittleness

Tendency of a material to break when deformed.

Specific Heat

Heat needed to raise temperature of a unit mass by 1 °C (or 1 K).

Solubility

Degree to which a substance dissolves in a solvent.

Elasticity

Ability of a material to return to original shape after stretching or compression.

Plasticity

Ability of a material to undergo permanent deformation under stress.

Magnetic Property

Capacity of a solid to be magnetised due to atomic alignment.

Malleability

Ability of a material to be hammered or rolled into thin sheets.

Ductility

Ability of a material, especially metals, to be drawn into wires.

Conductivity

Ability to allow heat or electricity to pass through.

Flammability

Ability of a substance to support combustion in air.

Combustibility

Capacity of a substance to react exothermically with oxygen.

Corrosive Property

Ability to damage metals through chemical or electrochemical reaction.

Oxidizing Property

Ability of a substance to cause another to lose electrons.

Reducing Property

Ability of a substance to donate electrons to another substance.

Physical Change

A change affecting appearance but not composition (e.g., melting ice).

Chemical Change

A change that alters chemical composition, forming new substances.

Endothermic Process

Process that absorbs energy (heat) from surroundings.

Exothermic Process

Process that releases energy (heat) to surroundings.

Density

Mass-to-volume ratio of a substance; ρ = m/V.

Pure Substance

Matter with fixed composition that cannot be separated by physical means.

Mixture

Physical combination of two or more substances; separable by physical methods.

Element

Simplest form of matter, composed of one type of atom; cannot be decomposed chemically.

Compound

Substance formed from two or more elements chemically combined in fixed ratios.

Molecule

Electrically neutral group of two or more atoms held by covalent bonds.

Homogeneous Mixture

Mixture with uniform composition throughout; also called a solution.

Heterogeneous Mixture

Mixture with visibly distinct components; non-uniform composition.

Sorting

Manual separation technique based on colour, size or shape.

Filtration

Separation technique that removes solids from liquids using a porous barrier.

Sedimentation

Process where heavier particles settle under gravity to form sludge.

Decantation

Separation by carefully pouring off a liquid, leaving sediment behind.

Distillation

Technique separating liquids based on differing boiling points.

Crystallization

Recovery of dissolved solids by partial evaporation of the solvent.

Chromatography

Separation of solutes based on differences in solubility and adsorption.

Thermolysis

Thermal decomposition of a compound on heating.

Electrolysis

Decomposition of a compound by passing electric current through its solution or melt.

Solid

State of matter with fixed shape and volume; particles tightly packed.

Liquid

State with definite volume but variable shape; particles close yet mobile.

Gas

State with neither fixed shape nor volume; particles far apart and free-moving.

Kinetic Molecular Theory

Model explaining properties of matter through motion and spacing of particles.

Law of Conservation of Mass

Total mass remains constant during a chemical reaction (Lavoisier).

Law of Definite Proportions

A compound always contains same elements in the same mass ratio (Proust).

Law of Multiple Proportions

When two elements form different compounds, masses combine in small whole-number ratios (Dalton).

Dalton’s Atomic Theory

Early theory stating atoms are indivisible, identical within an element, and rearranged in reactions.

Cathode Ray

Beam of electrons emitted from cathode in a vacuum tube.

Electron

Negatively charged subatomic particle discovered by J. J. Thomson.

Plum Pudding Model

Thomson’s model describing electrons embedded in a positively charged ‘pudding’.

Gold Foil Experiment

Rutherford’s experiment that revealed a small, dense, positive nucleus.

Nuclear Model

Rutherford’s atom: tiny positive nucleus with electrons in surrounding space.

Proton

Positively charged subatomic particle located in nucleus; mass ≈ 1 amu.

Neutron

Neutral subatomic particle in the nucleus; mass ≈ 1 amu.

Planetary Model

Bohr’s depiction of electrons orbiting nucleus in fixed energy levels.

Wave Mechanical Model

Modern model where electrons behave as waves occupying orbitals (Schrödinger).

Atomic Number (Z)

Number of protons in an atom’s nucleus; defines the element.

Mass Number (A)

Sum of protons plus neutrons in an atom.

Isotope

Atoms of the same element with differing numbers of neutrons (thus different A).

Percent Abundance

Relative proportion of an isotope in a natural sample of an element.

Average Atomic Mass

Weighted mean of isotopic masses based on natural abundances.

Isobar

Atoms of different elements with the same mass number but different atomic numbers.

Isotone

Atoms of different elements having the same number of neutrons.

Ion

Charged atom or molecule formed by loss or gain of electrons.

Cation

Positively charged ion (more protons than electrons).

Anion

Negatively charged ion (more electrons than protons).

Net Charge

Difference between number of protons and electrons in a species.

Atomic Mass Unit (amu)

1/12 the mass of a carbon-12 atom; standard unit for atomic masses.

Electromagnetic Radiation

Energy propagated as oscillating electric and magnetic fields travelling at the speed of light.

Wavelength (λ)

Distance between consecutive crests or troughs of a wave.

Frequency (ν)

Number of wave cycles passing a point per second; measured in hertz (Hz).

Amplitude

Height of a wave from midline to peak; relates to intensity.

Speed of Light (c)

Constant velocity of EM radiation in vacuum, 3.0 × 10⁸ m s⁻¹.

Quantum

Smallest discrete packet of energy, equal to hν (Planck).

Planck’s Constant (h)

Proportionality constant 6.626 × 10⁻³⁴ J s relating energy to frequency.

Bohr Model

Hydrogen atom model with electrons in quantised circular orbits.

Excitation

Process of an electron absorbing energy and moving to a higher orbital.

Relaxation

Electron transition from higher to lower energy level, emitting radiation.

Wave-Particle Duality

Concept that particles like electrons exhibit both wave and particle properties (de Broglie).

Heisenberg Uncertainty Principle

In quantum systems, position and momentum cannot both be known precisely at the same time.

Orbital

Three-dimensional region around nucleus where an electron’s probability density is high.

Quantum Numbers

Set of four numbers (n, l, ml, ms) that uniquely describe an electron in an atom.

Principal Quantum Number (n)

Indicates energy level and relative size of an orbital; positive integer.

Azimuthal Quantum Number (l)

Defines shape of orbital; integer from 0 to n − 1.

Magnetic Quantum Number (m_l)

Specifies orientation of an orbital; integer from –l to +l.

Spin Quantum Number (m_s)

Denotes spin direction of an electron, +½ or –½.

s Subshell

Subshell where l = 0; contains one spherical orbital.

p Subshell

Subshell where l = 1; contains three dumbbell-shaped orbitals.

d Subshell

Subshell where l = 2; contains five cloverleaf-shaped orbitals.

f Subshell

Subshell where l = 3; contains seven complex-shaped orbitals.

Aufbau Principle

Electrons fill orbitals from lowest to highest available energy.

Pauli Exclusion Principle

No two electrons in the same atom can share identical sets of quantum numbers.

Hund’s Rule

Electrons occupy degenerate orbitals singly with parallel spins before pairing.

Electron Configuration

Notation describing distribution of electrons among orbitals of an atom.

Orbital Diagram

Pictorial representation using boxes and arrows to show electron spins in orbitals.

Condensed Electron Configuration

Electron configuration abbreviated with preceding noble gas in brackets.