PHYSICAL CHEMISTRY

Created by: Chloewood1918
Created on: 04-06-18 13:31

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Atomic Structure
- Chemical properties of elements depend on atomic structure and arrangement of electrons around nucleus
- Physical Chemistry
  - Amount of substance
    - relative atomic mass and relative molecular mass
      - relative ATOMIC mass (Ar)
        carbon- 12
        is used as a baseline for relative atoimic mass - Mass spectrometer means we able to measure masses of individuals istopes accuratley
        
        reative atomic mass is define as ................. Ar = average mass of an atom / 1/12 of 1 atom of C-12
      - relative FORUMLA mass is used for ionic compounds because they don't exist as molecules. but have same symbol ( Mr)
      - relative MOCULAR mass (Mr)
        defined as ...... Mr = average mass of an entity / 1/12 of 1 atom of C-12
        
        Carbon-12
        compare mass of a molecule with that of an atom of Carbon -12
    - The mole and Avogradro constant
      - Avogradro constant
        defined as the number of atoms in 12g of Carbon-12
        
        actual number of atoms in 1g of hydrogen is huge and usually written as 6.022 x 10^23
      - The mole
        the amount of substance that contains 6.022 x 10^23 particles
        
        to find moles
        mass/ Mr
        
        concentration x volume / 1000
        
        to find concentration
        number of moles / volume
    - ideal gas equation
      - PV = nRT
        n= moles
        
        V= volume
        
        R= gas constant
        
        P= pressure
        
        T = temperature
    - Empirical formula
      - is the simplest whole number ration of atoms of each element in a compound
      - to find empirical formula
        1. find masses of elements present 2. work out number of moles 3. convert No. of moles into a whole number ratio
      - molecular formula gives the actual number of atoms of each element of the compound
        Mr/ mass of empirical formula
    - Blanced eqations and assoiciate equations
      - balanced equations
        Make sure there are the same number reactants and products on each side
      - ionic equations
        1.write out equation 2. note which ions are present 3. rewrite equation with ions 4. get rid of that appear on both sides - these arte spectator ions
      - Atom economy
        mass of desired product / total mass of reactants x 100
      - percentage yield
        the number of moles of a specified product / theoretical maxium number of moles of the product x 100
    - Chemists use amount of a subatnce in moles because one mole of a subatnce always contains same number of entiites of the substance
- Arrangement of electrons in orbritals linked to the way in which elemnets are orgsnised in periodic table
- Measure mass of atoms using mass spectrometer
- Fundamental particles
  - Protons
    - Charge = +1
    - Mass = 1
  - Electrons
    - Charge = -1
    - Mass = very small
  - Neutrons
    - Charge= no charge
    - Mass = 1
  - Carbon - 12
    - Chosen as its mass per nucleon is around average
      - Therefore an atomic mass unit is defined as 1/12th of the mass of one atom of Carbon-12
- Mass number and isotopes
  - Atom is named after number of protons in nucleus
  - The number of protons in the nucleus of an atom is called the ATOMIC NUMBER
    - It has the symbol Z
  - The MASS NUMBER is the sum of protons and neutons in neuclus of atom
    - it has the symbol A
  - ISOTOPES are atoms with the same atomic number but different mass numbers
    - They therefore differ in relative atomic mass but have same chemical properties
  - Time Of Flight (TOF) Mass Spectrometer
    - it can be used to: find the abundance and mass of each isotope in an element allowing us to determine relative atomice mass...
      - .....And find the relative molecular mass of substances made from molecules
    - stage 1
      - Ionisation
        Electronspray
        sample dissolved in a volatile solvent. injected into mass spectrometer
        Particles are ionised by gaining a proton from electron spray
        
        Its used for substances with higher molecular mass
    - stage 2
      - Acceleration
        Positive ions are then accelerated using electric field to give them all the same kinetic energy
        Lighter particles have a faster velocity and heavier particle have a slower velocity
    - Stage 3
      - Flight tube ( ion drift )
        Ions travel through hole in the negatively charged plate into a ube
        TOF of each paricle depends on its velocity and therefore mass
    - Stage 4
      - Detection
        + Ions hit - charged electric plate. the + ions are discharged by gaining electrons from the plate
        This generates a movement of electrons and an electric current is measured
        it can be used to identify elements and determine relative molecular mass
    - Gives accurate information about relative isotopic mass and also the relative abundance of isotopes
- electron configuration
  - FIRST IONISATION ENERGY Is the energy required to remove one mole of the most loosely held electrons from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of +1
  - The maximum No. of electrons in each shell are:
    - Shell 1 :
    - shell 2:
    - shell 3:
    - Sub shells
      - D: 10 electrons
      - P: 6 electrons
      - F: 14 electrons
      - S: 2 electrons
    - Orbitals
      - S orbital
      - P orbitals
  - ionisation energies
    - SECOND IONISATION ENERGY bigger than 1st - when 1st electron is removed a + ion forms - increases attraction between remaining electrons so energy reuired to remove nexdt electron is larger
Chosen as its mass per nucleon is around average
- Therefore an atomic mass unit is defined as 1/12th of the mass of one atom of Carbon-12

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PHYSICAL CHEMISTRY

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