Chemistry Paper 1

  • Created by: KateS03
  • Created on: 14-04-19 11:34
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    • 1. Atomic Structure & the Periodic Table
      • atoms
        • the nucleus - protons and neutrons, radius of 1x10-14m, positive charge
        • the electrons - in electron shells, move around nucleus, negative charge, no mass
        • particle : mass : charge - proton:1:+1, neutron:1:0, electron:tiny:-1
        • number of protons equals number of electrons
        • atomic number = protons (small), mass number = protons & neutrons (big)
      • elements
        • they are atoms with the same atomic number
        • isotopes have a different number of neutrons
        • relative atomic mass = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes
      • compounds
        • when elements react, atoms combine with other atoms to form compounds
        • from a metal and non-metal: there are ions, ionic bonding
        • from two non-metals: there are molecules, covalent bonding
        • compounds can be represented by formulas
        • the properties can be very different
      • mixtures
        • they can be easily separated as there is no chemical bond between the different parts
        • the properties are the properties of the separate parts
        • paper chromato-graphy - separate dyes and inks: draw a pencil (insoluble) line, add ink, put in solvent, move up at different rates, called a chromato-gram
        • filtration separates insoluble solids from liquids
        • to separate soluble solids from a solution, either evaporate or crystallise
        • rock salt - sand & salt - can be separated by filtration and crystallisation
      • atom history
        • 1. 19th century - atoms were described as solid speres
        • 2. 1897 - Thomson's experiments showed there were tiny negative electrons - plum pudding model
        • 3. 1909 - Rutherford did the alpha particle scattering experiment showing there was a positive nucleus - nuclear model
        • 4. Bohr proposed that electrons obit in fixed shells - nuclear model
        • 5. Rutherford later showed that the nucleus can be divided into smaller particles, the same charge as a hydrogen nucleus called protons, then neutrons were found - modern nuclear model
      • distillation
        • simple distillation - separate out a liquid from a solution - it is heated, then one part evaporates, vapour condenses
        • fractional distillation - separate out a mixture of liquids - put a fractionating column on, then heat, one part evaporates, vapour condenses, next liquid can be separated
        • it's used to separate out mixtures which contain liquids
      • electronic structure
        • electron shell rules: always occupy shells, lowest levels are filled first, certain numbers are allowed in shells, atoms prefer to have full shells, most atoms don't have full outer shells
        • the number of electrons in each shell: 2, 8, 8, 8...
        • outer shells that aren't full want to react to fill it
      • modern periodic table
        • elements are laid out in order of increasing atomic (proton) number, meaning there are repeating patterns in  the properties
        • metals are to the left, non-metals are to the right
        • elements with similar properties form columns - groups
        • the group number says how many electrons are in the outer shell
        • the rows - periods - represent another full shell of electrons
      • periodic table
        • in early 1800s, elements were arranged by atomic mass
        • there was two ways to categorise elements: physical & chemical properties, or atomic mass
        • scientists didn't know about the structure, protons, neutrons or electrons - there was no atomic number
        • 1869 - Dimitri Mendeleev overcame some problem, he organised the 50 known elements and left gaps
        • Mendeleev put them in atomic mass, but switched some if the properties didn't fit
        • gaps were left so elements with similar properties stayed in the same group - isotopes show he was right not to place them in a strict order
      • metals & non-metals
        • metals from positive ions wen they react
        • metals to the left - few outer shell electrons - don't need much energy to remove electrons
        • metals to the bottom - weaker attraction with outer shell electrons - don't need much energy to remove electrons
        • all metals have metallic bonding causing similar properties - strong, malleable, conductors, hbp, hmp
      • group 1
        • they have one electron in the outer shell making them reactive, soft & low density
        • as you go down: increasing reactivity, lmp & lbp, higher atomic mass
        • they don't need much energy to lose the one electron so form 1+ ions readily
        • they only form ionic compounds: generally white solids that dissolve in water to form colourless solutions
        • reaction with: water - hydrogen gas & metal hydroxide & more reactive metals: more violent & more energy given out, chlorine - white metal chlorine salts & more reactive metals: more vigorous, oxygen - metal oxide
        • compared to transition metals: they are more reactive & less dense, strong, hard & much lmp
      • transition matals
        • they are in the centre of the periodic table
        • they are conductors, dense, strong, shiny
        • they can have more than one ion (e.g. + & 2+)
        • they are often coloured
        • they can be used as a good catalyst
      • group 7
        • non-metals with coloured vapours: fluorine - very reactive, poisonous yellow gas, chlorine - fairly reactive, poisonous dense green gas, bromine - dense, poisonous, red-brown volatile liquid, iodine - dark grey crystalline solid or a purple vapour
        • as you go down: less reactive (harder to gain, less attraction), hmp & hbp, higher atomic mass
        • they exist as molecules which are pairs of atoms
        • can form molecular compounds - sharing electrons via colanent bonding with outer non-metals forming simple molecular structures
        • can form ionic bonds with metals - make 1- ions called halides
        • more reactive ones will displace less reactive ones
      • group 0
        • they are inert, non-flammable colourless gases as they have eight electrons in the outer shell
        • they exist as monatomic gases - not bonded together
        • as you go down : the bp increases as there is in an increase in the numbr of electros in each atom leading to greatr intermolecular forces

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