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GCSE Chemistry- Topic 1

Atoms and Elements

  • Atoms: The basic building blocks of matter, consisting of protons, neutrons, and electrons.

  • Elements: Pure substances made of only one kind of atom, listed in the periodic table.

Compounds and Chemical Equations

  • Compounds: Substances formed when two or more elements chemically bond. Example: H₂O (water).

  • Chemical Equations: Representations of chemical reactions, showing reactants turning into products, e.g., A + B → C.

Mixtures and Chromatography

  • Mixtures: Combinations of two or more substances that retain their individual properties. Example: Air.

  • Chromatography: A technique for separating mixtures based on differences in the components’ movement through a medium.

Separation Techniques

  • Techniques used to separate components of mixtures, including:

    • Filtration: Separates solids from liquids.

    • Evaporation: Removes liquid to leave a solid.

Distillation

  • Distillation: A process used to separate mixtures based on differences in boiling points. Used for purifying liquids.

History of the Atom

  • Early models by Democritus and Dalton proposed atoms as indivisible.

  • Thomson discovered the electron, leading to the “plum pudding” model.

Electronic Structure

  • Arrangement of electrons in an atom’s shells, important for understanding chemical bonding and reactivity.

Development of the Periodic Table

  • Mendeleev arranged elements by atomic mass; later atomic number became the organizing principle.

The Modern Periodic Table

  • Organized by increasing atomic number, revealing periodic trends in properties.

Metals and Non-Metals

  • Metals: Typically shiny, conductive, ductile, and malleable. Found on the left side of the periodic table.

  • Non-Metals: Dull, insulating, and brittle. Located on the right side of the periodic table.

Group 1 Elements

  • Known as alkali metals (e.g., Li, Na, K), highly reactive and soft, with low melting points.

Group 7 Elements

  • Known as halogens (e.g., F, Cl, Br), highly reactive non-metals with varying states at room temperature.

Group 0 Elements

  • Known as noble gases (e.g., He, Ne, Ar), extremely unreactive with complete electron shells, used in neon lights and other applications.