Lecture Notes: Matter, Atomic Theory, Nuclear Chemistry, and Periodic Trends (Vocabulary Flashcards)

A set of vocabulary flashcards covering essential terms from matter, atomic theory, nuclear chemistry, and periodic trends.

Matter

Anything that has mass and volume.

State of Matter

Forms matter can take: solid, liquid, or gas; each with distinct properties.

Solid

Rigid state with fixed shape and fixed volume.

Liquid

Definite volume; takes the shape of its container.

Gas

No fixed shape or volume; expands to fill the container.

Physical Property

A characteristic that can be observed or measured without changing the substance into a different substance.

Melting Point

Temperature at which a solid changes to a liquid.

Boiling Point

Temperature at which a liquid boils and becomes a gas.

Freezing Point

Temperature at which a liquid becomes a solid.

Solubility

Ability of a substance to dissolve in a solvent.

Chemical Property

A characteristic observed during a chemical reaction; ability to form a new substance.

Biodegradability

Capacity of a material to decompose through microorganisms.

Combustion

Chemical reaction with oxygen producing heat and light.

Element

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

Atom

Basic unit of an element; composed of a nucleus (protons and neutrons) with electrons surrounding it.

Compound

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

Pure Substance

Matter with a fixed composition; either an element or a compound.

Mixture

Matter made of two or more pure substances with variable compositions.

Democritus

Ancient philosopher who proposed that matter is made of indivisible particles called atoms.

Dalton's Atomic Theory

Atoms are the building blocks of elements; atoms of an element are identical; compounds form by combining different elements in simple ratios.

Solid Sphere Model

Dalton's early model: atoms are tiny, indestructible spheres.

Cathode Ray

Experiment leading to the discovery of electrons; rays are smaller than atoms.

Plum Pudding Model

Thomson's model: a positively charged sphere with embedded electrons.

Nucleus

Center of the atom containing protons and neutrons; most mass concentrated here.

Proton

Positively charged particle in the nucleus.

Neutron

Electrically neutral particle in the nucleus.

Electron

Negatively charged particle orbiting the nucleus.

Rutherford Gold Foil Experiment

Experiment that revealed a dense, positively charged nucleus.

J.J. Thomson

Discovered electrons; proposed Plum Pudding Model.

Ernest Rutherford

Proposed Nuclear Model; discovered the nucleus and protons.

James Chadwick

Discovered neutrons.

Bohr Model

Planetary model: electrons orbit the nucleus in fixed energy levels.

Uncertainty Principle

We cannot know both position and momentum of a particle exactly.

Schrödinger Model

Quantum Mechanical Model; electrons described by wave functions; orbitals.

Orbitals

Regions in space with high probability of finding an electron; shapes include s, p, d, f.

Principal Quantum Number (n)

Indicates the main energy level; n = 1, 2, 3, …

Azimuthal Quantum Number (l)

Sublevel type (s, p, d, f) indicating orbital shape.

Magnetic Quantum Number (m_l)

Orientation of an orbital; values range from -l to +l.

Spin Quantum Number (m_s)

Intrinsic spin of an electron; values are +1/2 or -1/2.

Aufbau Principle

Electrons fill the lowest energy orbitals first.

Hund's Rule

Electrons in a subshell occupy degenerate orbitals singly before pairing.

Electron Configuration

Arrangement of electrons in atoms in shells and subshells (e.g., 1s2 2s2 2p6).

Electron Cloud

Probability distribution of where an electron is likely to be found.

Isotope

Atoms of the same element with different mass numbers due to different neutron numbers.

Atomic Mass Unit (amu)

1/12th the mass of a carbon-12 atom; standard mass unit for atoms.

Fundamental Forces

Gravity, Electromagnetic, Strong Nuclear, Weak Nuclear.

Nuclear Decay

Unstable nucleus emits radiation and transforms into a different nucleus.

Nuclear Transmutation

A nucleus changes into a different nuclide, often via a reaction.

Alpha Particle

Helium-4 nucleus (2 protons and 2 neutrons); charge +2.

Beta Particle

Electron emitted from the nucleus (β−).

Positron

Positive electron emitted in beta-plus decay.

Gamma Radiation

High-energy photon emitted from a nucleus; highly penetrating.

Mass Number (A)

Total number of protons and neutrons in a nucleus.

Atomic Number (Z)

Number of protons in the nucleus; defines the element.

Ionization Energy

Energy required to remove an electron from a neutral atom in gas phase.

Electronegativity

Atom's tendency to attract electrons in a chemical bond.

Electron Affinity

Energy change when an atom gains an electron.

Atomic Radius

One-half the distance between the nuclei of two identical atoms.

Metallic Character

Tendency of an element to lose electrons; increases down a group and decreases across a period.