Summary-Unit 1 Chemistry

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Atomic Structure

  • Fundamental particles=electrons, neutrons, protons 
  • Proton charge=+1, why hydrogen is sometimes called/used as a proton 
  • Electrons charge=-1
  • Protons and neutrons held together by a nuclear force 
  • Electrons held by electrostatic forces 
  • Mass of proton=1.673x10-27
  • Mass of neutron=1.675x10-27
  • Mass of electron=0 
  • Shells fill up- 2,8,18 
  • Atomic number=proton number 
  • Mass number=no. of protons + no.of neutrons 
  • Isotope=same number of protons but different number of neutrons 
  • Isotopes react in the same way because they have the same electron configuration 
  • Mass spectrometer kept in a vaccum so ions do not react with air molecules 
  • Sample in gaseous state so it can be injected directly 
  • Ionisation-elctron gun fires high speed electrons, knocks out an electron
  • Acceleration-negatively charged plates, lighter ions travel faster 
  • Deflection-magnetic field, lighter ions and 2+ ions deflected more, 
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Atomic Structure Part 2

  • Detection- ions strike detector, gain an electron, lose charge, create current relative to abundance 
  • S orbital=2
  • P orbital=3x2=6 
  • D orbital=5x2=10
  • Orbitals of lower energy are filled out first 
  • Orbitals fill singly and then pair up due to electron repulsion theory 
  • Ionisation energy-energy required to remove 1mole of electrons from 1 moles of atoms in gaseous state
  • Second IE is higher than the first, as an electron is being removed from a positive ion
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Amount of Substance

  • The relative atomic mass is the weighted average mass of an atom of an element relative to 1/12 the relative atomic mass of an atom of carbon-12 
  • Moles=mass/molar mass 
  • Moles=concentration x volume 
  • Ideal gas equation=PV=nRT, volume in m3
  • C to K: +273 
  • 1 dm3=1000cm3
  • Atom economy= Mass of desired/ total mass of reactants x100 
  • Percentage yield=number of moles of specified product/ theoretical number of moles of product x100
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Bonding

  • Ionic-between non metals and metals, transfer of electrons, held together through electrostatic attraction between oppositely charged ions 
  • Covalent-non metals only, a shared pair of electrons. Held together by electrostatic attraction between psotive nuclei and shared electrons 
  • Dative Covalent-one atom provides both electrons, e.g. ammonium ion 
  • Metallic-metals only, postive ions attracted to the sea of delocalised electron,Mg3+=3 electrons 
  • Crystals: Molecular, Macromolecular,Giant Ionic Lattice, Metallic 
  • Electronegativity is the power of an atom to attract electron density to itself in a covalent bond 
  • Intermolecular: 
    • Van De Waals 
    • Dipole Dipole 
    • Hydrogen Bonding 
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Bonding Part 2

  • Most electronegative elements- F,O, N
  • Ice is less dense than water as molecules are more spread out
  • Turning a solid to liquid=fusion. Energy supplied to do this is called enthalpy change of fusion 
  • Liquid to gas=vaporisation. Energy supplied to do this is called enthalpy change of vaporisation
  • 2 electrons=linear=180 
  • 3 electrons=no lone pairs=trigonal planar=120
    • 1 lone pair=non linear trigonal planar=120
  • 4 electrons=no lone pair=tetrahedral=109.5
    • 1 lone pair=trigonal pyramidal=107
  • 5 electrons=no lone pairs=trigonal bypyramid=120, 90 
  • 6 electrons= no lone pairs=octahedral= 90 
  • Repulsion theory 
    • lone pair-lone pair 
    • lone pair-bonding pair 
    • bonding pair-bonding pair 
  • Every lone pair takes 2 degrees off bond angle
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Periodicity

  • Period 3 Trends: 
    • Na, Mg, Al- giant metallic=high b.p, increase across as the charge on the ion increases 
    • Si-macromolecular=high b.p 
    • P, S, Cl- molecular, order S8>P4>Cl2, depends on number of VDW+size of molecule 
  • Atomic radii decreases across a period due to increased nuclear charge, which pulls electrons closer to the nucleus and there is no extra sheilding 
  • Atomic radii increases down a group due to extra shielding and distance from the nucleus 
  • First ionisation energy=the energy required to convert 1 mole of isolated gaseous atoms into 1 mole of singly positive gaseous ions 
  • For example: Na(g)-->Na+(g)+e-
  • First ionisation energy increases across a period due to increased number of protons, nuclear charge, therefore its increasingly harder to remove an electron 
  • First ionisation energy decreases down a group, increased shielding and distance from the nucleus, easy to remove 
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Periodicity Part 2

  • Drop in ionisation energy-groups 2 and 3 
    • Mg loses a 3s electron 
    • Al loses 3p electron 
    • P electron is already higher energy than the s, so its easier to remove 
  • Drop in ionisation energy- groups 5 and 6 
    • P has no paired electrons because each p electron is in a different p orbital 
    • S has 2 p electrons paired, so one is easier to remove due to electron repulsion theory 
  • There is a little increase in the first and second ionisation energy because in the second an electron is trying to be removed from a positive ion, which is harder 
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Introduction to Organic Chem

  • Organic chemistry=carbon compounds 
  • Structural formula-unique arrangement of atoms in a molecule without showing the bonds 
  • Functional Groups 
    • Alkanes=ane    Alkenes=ene      Haloalkanes 
    • Alcohols=ol       Aldehydes=al     Ketones=one 
    • Carboxylic acid=oic acid 
  • A homologous series is a family of organic compounds Isomers=molecules that have the same molecular formula but arranged differently 
    • Same general formula 
    • Show trends in physical properties e.g b.p 
  • Structural isomerism=same molecular formula but different structural formula 
    • Positional=functional group attached to main chain at different points 
    • Functional group=the functional group is different 
    • Chain=different arrangement of hydrocarbon chain e.g. branching 
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Alkanes

  • Saturated hydrocarbons 
  • CnH2n+2
  • Can be unbranched chains, branched, cycloalkanes 
  • Almost non polar because there is only a small difference in electronegativity 
  • B.p increase with chain length 
  • Branched alkanes have lower b.p as there more spread out, VDW are less effective 
  • Alkanes are insoluble in water 
  • Relatively unreactive 
  • Crude oil is seperated through fractional distillation 
  • Cracking is done to create more useful products and some of the products are alkenes which are more reactive 
  • Thermal cracking=done under high temp and pressure, C-C bond is broken in a way where one electron(free radical) goes to each carbon. There is not enough H, so one of the products is an alkene 
  • Catalytic cracking=lower temp and pressure compared to therma, uses a zeolite catalyst(honeycomb structure), mainly produces motor oil 
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Alkanes Part 2

  • Pollutants: 
    • Carbon monoxide-poisinous gas 
    • Carbon-smog and exacerbate asthma 
    • Nitrogen oxide- forms in a petrol engine with a high temp and a spark 
    • CO2 
    • SO2-acid rain
  • Sulphur dioxide is removed using CaCO3 or CaO, absorb SO2 to form gypsum 
  • Catalytic converters
    • Use a platinum catalyst 
    • 2CO+2NO---->N2+2CO2
  • Carbon neutral=activities that produce no net carbon dioxide emissions 
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