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.