CHEMISTRY

Atom

Smallest unit of an element; building blocks of all matter.

Atomic Number

Number of protons in an atom, which is also equal to the number of electrons in a neutral atom.

Mass Number

Total number of protons and neutrons in the nucleus of an atom.

Leucippus & Democritus

Philosophers who proposed that all matter is made of tiny, indivisible particles called 'atomos'.

John Dalton's Billiard Ball Model

Model suggesting that atoms are solid spheres and atoms of the same element are identical.

J.J. Thomson's Plum Pudding Model

Model proposing that the atom is a positively charged sphere with scattered electrons; discovered the electron.

Ernest Rutherford's Nuclear Model

Model that introduced the concept of a dense, positively charged nucleus where protons reside, with electrons orbiting around.

Niels Bohr's Planetary Model

Model stating that electrons orbit the nucleus in fixed energy levels.

James Chadwick

Discovered the neutron, a neutral particle within the nucleus of an atom.

Erwin Schrödinger's Quantum Mechanical Model

Model stating that electrons move in probability clouds or orbitals, making their exact locations uncertain.

Matter

Anything that has mass and occupies space.

Non-Matter

Things that do not have mass or volume, such as light and heat.

Pure Substance

A material with a fixed composition that cannot be physically separated.

Element

A pure substance consisting of one type of atom.

Compound

A pure substance made of two or more different types of atoms chemically bonded together.

Homogeneous Mixture (Solution)

A mixture that is uniform in composition; components are evenly distributed.

Heterogeneous Mixture

A mixture with visibly different substances or phases.

Colloid

A type of mixture where particles do not settle and remain suspended (e.g., milk, fog).

Suspension

A mixture in which large particles settle out over time (e.g., muddy water).

Filtration

A separation method that uses filter paper and funnel to separate insoluble solids from liquids.

Decantation

Separation of liquid from solid after solid has settled, pouring out without disturbing the solid.

Distillation

A separation process that uses boiling and condensing to separate liquid from a mixture.

Chromatography

A method for separating components of a mixture based on their movement through a stationary phase.

Physical Change

A change that affects one or more physical properties of a substance without altering its chemical identity.

Chemical Change

A change that results in the formation of a new substance with different properties.

State of Matter

The distinct forms that different phases of matter take on, includes solid, liquid, gas, plasma, and Bose-Einstein condensate.

Solid

A state of matter with a definite shape and volume; particles are tightly packed.

Liquid

A state of matter with a definite volume but no definite shape; particles can move past each other.

Gas

A state of matter with no definite shape or volume; particles move freely and rapidly.

Plasma

An ionized gas with very high energy, found in stars and neon signs.

Bose-Einstein Condensate (BEC)

A state of matter formed at extremely low temperatures where atoms clump together and act as a single particle.