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  • Atoms and Elements

    • About 100 different elements make up all substances.

    • Periodic Table: A list of elements represented by chemical symbols (e.g., Na for sodium, O for oxygen).

    • Elements are arranged into columns (groups) with similar properties.

  • Chemical Equations

    • Show reactants (starting substances) and products (substances made in reaction).

    • Word equations use names; symbol equations show numbers/types of atoms.

    • Law of conservation of mass: atoms are neither created nor destroyed.

    • Balancing equations: same number/type of atoms on both sides.

    • State symbols: s (solid), l (liquid), g (gas), aq (aqueous).

  • Separating Mixtures

    • Mixture: Two or more substances not chemically combined.

    • Separation techniques: filtration, crystallization, distillation.

    • Filtration: Separates insoluble from soluble substances (e.g., sand from salt).

    • Crystallization: Separates soluble solid from solvent (e.g., salt from solution).

    • Distillation: Separates solvent from soluble solids (e.g., seawater to saltwater).

  • Fractional Distillation and Paper Chromatography

    • Fractional Distillation: Separates miscible liquids (e.g., ethanol and water).

    • Paper Chromatography: Separates substances in solutions based on solubility (e.g., food colorings).

  • History of the Atom

    • Early ideas by Ancient Greeks; Dalton proposed atoms as indivisible spheres.

    • Thomson discovered electrons (plum pudding model).

    • Rutherford's nuclear model: atoms have a nucleus with positive charge.

    • Bohr revised to show electrons in energy levels; Chadwick discovered neutrons.

  • Structure of the Atom

    • Nucleus: Contains protons (positive) and neutrons (neutral).

    • Electrons (negative) orbit around the nucleus; atom's charge is neutral.

    • Atomic number: Number of protons (and electrons); mass number: protons + neutrons.

  • Ions, Atoms, and Isotopes

    • Ions: Charged atoms; gain/loss of electrons creates negative/positive ions.

    • Isotopes: Atoms of the same element with different neutron counts.

  • Electronic Structures

    • Electrons are arranged in shells (energy levels).

    • Maximum electrons per shell: 2 (first), 8 (second), 8 (third).

    • Example: Sodium (Na) electronic structure is 2, 8, 1.

    • Elements in the same periodic group have the same amount of electrons in their outer shell.

    • Noble gases (Group 0) are unreactive with stable electron arrangements (8 electrons, except He with 2).