SB5-7 Chemistry

    Cards (65)

    • An anion is a negative ion because it gains electrons
    • A cation is a positive ion because it has lost electrons
    • Ionic bonding is bonding between a non-metal and metal by the transfer of electrons
    • Ionic compounds:
      • lattice structure
      • held together by strong forces of attraction between oppositely charged ions
      • form crystals because of lattice structure
    • Ionic compounds are formed by the loss and gain of electrons
    • Al3+ + O2- = Al2O3
    • Properties of ionic compounds:
      • very high melting and boiling points
      • only conduct when molten or aqeous
      • soluble
      • lattice structure
    • Electrical conductivity of ionic compounds:
      Do not conduct when in a solid state but heating them up to molten state or putting them in an aqueous solution breaks the electrostatic forces of attraction between the ions so the electrons are free to move and carry a charge
    • Ionic compounds have high boiling points because lots of energy is needed to overcome the strong electrostatic forces of attraction between the oppositely charged ions
    • Covalent bonds are formed between non-metals that share pairs of electrons in order to get full outer shells
      Forms MOLECULES
    • Valency = the number of covalent bonds formed by atoms of different elements
    • Hydrogen, oxygen and chlorine go around in pairs, sharing electrons
    • Examples of molecular compounds are
      • Water (H2O), H-O-H
      • Hydrogen chloride (HCl), H-Cl
      • Cardon dioxide (CO2), O=C=O (double)
    • Properties of molecular compounds:
      • weak intermolecular forces
      • low melting and boiling points
      • cannot conduct electricity
    • Molecular compounds have low m&bp as the forces don't take much energy to overcome
    • Polymers are chains or small simple molecules (monomers), longer chains have stronger intermolecular forces, usually contain carbon atoms
    • Examples of polymers:
      • Poly (ethene)
      • Poly (styrene)
    • An allotrope is a different structural form of the same element]
    • DIAMOND:
      Structure - giant covalent, tetrahedral arrangement, 4 bonds per atom
      Properties - hard, high melting and boiling points, electrical insulator, strong covalent bonds
      Uses - cutting heads when drilling rocks (very hard)
    • GRAPHITE:
      Structure - giant covalent, hexagonal layered structure, weak forces between layers, 3 bonds per atom
      Properties - soft, high melting and boiling points, electrical conductor, cheap, unreactive, strong covalent bonds
      Uses - lubricant (layers slide past each other)
    • Graphite conducts electricity because not all of the electrons are held in bonds, some are delocalised and free to carry a charge
    • GRAPHENE:
      Structure - not a simple molecule, sheet of carbon atoms, 1 atom thick
      Properties - lightest known material, electrical conductor, very strong covalent bonds
      Uses - can be rolled into a tube
    • FULLERENES: Molecules made up of carbon atoms only, with hollow shapes
      Structure - simple molecules, often tubular or spherical
      Properties - low melting and boiling points, soft and slippery, 3 bonds per atom, weak intermolecular forces, strong covalent bonds
      E.G C60 (bucky ball)
    • Metal structure:
      • lattice of positive ions
      • sea of delocalised electrons
      • packed closely together in layers
    • Metals are malleable because the layers of ions slide over each other but the sea of electrons hold the ions together so instead of breaking the metal changes shape
    • Metals are conductors because the electrons are delocalised and free to move this means they can carry a charge and form an electric current and flow towards the positive terminal
    • Properties of metals:
      • malleable
      • good conductors
      • shiny when polished
      • high melting and boiling points
    • Metallic bonding is the electrostatic attraction between delocalised electrons and the positive metal ions
    • An acid is a substance that has a pH less than 7 and produces excess H+ ions in water
    • An alkali is a substance with a pH more than 7 and that produces excess OH- ions in water
    • Hazard symbols are important because:
      • universal, no language barrier
      • indicates the danger of the substance
      • gives information about how to work safely with the substance
    • An indicator is a substance that changes colour depending on the pH of a solution
    • Main acids:
      • HCl - hydrochloric
      • H2SO4 - sulfuric
      • HNO3 - nitric
      • CH3COOH - ethanoic
    • Main alkalis:
      • sodium hydroxide - NaOH
      • calcium hydroxide - CaOH2
      • potassium hydroxide - KOH
      • ammonium hydroxide - NH4OH
    • Universal indicator goes red in acid and blue in alkalis
    • Litmus paper goes red in acids and blue in alkalis
    • Phenolphthalein goes pink in alkalis and colourless in acids
    • Methyl orange goes red in acids and yellow in alkalis
    • If the concentration of H+ ions is increased by a factor of 10, the pH decreases by 1 and vice versa
    • A concentrated acid is one thst has a lot of solute dissolved per unit volume/ has a high concentration of H+ ions
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