Summary-Unit 1 Chemistry
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- Created by: Sophie Perrett
- Created on: 29-04-15 22:30
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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