atomic structures and mixtures

Atom

The smallest unit of matter, consisting of protons, neutrons, and electrons.

Element

A substance made up of only one type of atom.

Compound

A substance a substance made up from 2 or more different elements chemically bonded together.

Mixture

A combination of two or more substances joined together but not chemically bonded.

Filtration

Separates insoluble solids from liquids.

Crystallization

Forms solid crystals from a solution.

Distillation

Separates liquids based on boiling points.

Chromatography

Separates substances based on solubility.

Simple distillation

Separates a solvent from dissolved substances (e.g., water from salt).

Fractional distillation

Separates multiple liquids based on boiling points (e.g., ethanol from water).

Rutherford's gold foil experiment

Revealed that atoms have a small, dense nucleus surrounded by empty space.

Plum pudding model

Suggested a spread-out charge, but was shown to be incorrect by Rutherford.

Bohr's model

Introduced that electrons move in fixed energy levels around the nucleus.

Protons

Subatomic particles with a charge of +1.

Neutrons

Subatomic particles with a charge of 0 (neutral).

Electrons

Subatomic particles with a charge of -1.

Ion

An atom that becomes charged by gaining or losing electrons.

Cation

A positive ion formed by losing electrons.

Anion

A negative ion formed by gaining electrons.

Mass of protons

Mass = 1.

Mass of neutrons

Mass = 1.

Mass of electrons

Mass ≈ 1/1836.

Size of an atom

Approximately 0.1 nanometers (1 × 10⁻¹⁰ m).

Relative atomic mass (RAM)

[ RAM = (Mass of isotope 1 × Abundance) + (Mass of isotope 2 × Abundance) / 100 ]

Isotopes

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

Examples of isotopes

Carbon-12 (Stable) & Carbon-14 (Radioactive); Uranium-235 (Used in nuclear fuel) & Uranium-238 (More abundant).

Electron arrangement

Electrons are organized into energy levels (shells) around the nucleus.

Maximum electrons in first shell

Maximum 2 electrons.

Maximum electrons in second shell

Maximum 8 electrons.

Maximum electrons in third shell

Maximum 8 electrons.

Electron configuration for sodium (Na)

2, 8, 1 (1 electron in the outer shell, making it reactive).