Chemistry Chapter One

• Atoms


  Smallest particles that make up all substances
• Elements


  Substances made up of one type of atom
• Compounds


  Substances containing atoms of two or more elements chemically combined
• Mixtures


  Contain two or more elements not chemically combined, can be separated by physical processes
• Chemical formula


  Representation of a compound using chemical symbols (e.g. H₂O, Na₂SO₄)
• Chemical reaction


  Process where the chemical composition of a substance is changed, with reactants becoming products
• The total mass of reactants is always equal to the total mass of the products in a chemical reaction. No atoms are lost or made.
• Filtration


  Used to separate insoluble solids from liquid solutions, where the liquid passes through but the solids cannot
• Crystallisation


  Used to obtain a soluble solid from a solution by heating to evaporate some of the solvent
• Simple distillation


  Used to obtain a solvent from a solution by heating, where the solvent vapour is trapped and condensed
• Fractional distillation


  Used to separate mixtures with components of different boiling points, where the lowest boiling point component is collected first
• Chromatography


  Used to separate different coloured components of a mixture as the solvent moves along paper
• Water samples can be analysed and purified using techniques like pH testing, distillation, and measuring dissolved solids
• Subatomic particles


  Protons, neutrons, and electrons that make up atoms
• Atomic number


  Number of protons in the nucleus of an atom
• Mass number


  Total number of protons and neutrons in the nucleus of an atom
• Isotopes


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


  Atoms that have gained or lost electrons, giving them a positive or negative charge
• Electronic configuration


  The arrangement of electrons in an atom's energy levels or shells
• Noble gases


  • He, Ne, Ar, Kr, Xe, Og
• Alkali metals

  • Li, Na, K, Rb, Cs, Fr
• Alkali metals


  • Have one electron in outer shell, have low melting and boiling points, become more reactive down the group
• Alkali metal reacts with water


  Forms metal hydride and hydrogen gas
• Halogens


  • Non-metals with seven electrons in outer shell, reactivity decreases down the group, react with metals to form ionic salts
• More reactive halogen


  Displaces less reactive halogen from aqueous salt solution
• The periodic table was developed over time, with contributions from scientists like Newlands, Mendeleev, and others