Chemistry 1.2

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  • Created by: selen.
  • Created on: 19-04-15 11:19
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  • Chemistry 1.2
    • Ionisation energy
      • energy required to remove one e¯ from each atom in 1mol(g) atoms to form 1mol of 1+ ions(g)
      • Factors affecting ionisation energy:
        • Nuclear charge
          • greater nuclear attraction = greater attraction on valence e¯
        • Atomic radius
          • greater the atomic radius, smaller nuclear attraction
        • E¯ shielding
          • inner e¯ repel outer ones
            • the more inner shells, the more shielding & less attraction between nucleus and valence e¯
      • Successive ionisation energies
        • the measure of energy required to remove each e¯ in turn
          • e.g. for Li there are 3 valence e¯
            • Li = Li+ + e¯ Li+=Li2+ + e¯ Li2+=Li3++e¯
        • Each successive ionisation energy is larger than the one before
          • as each e¯is removed there is less repulsion bwn e¯ so each shell is pulled in to nucleus
            • so nuclear attraction increases so more energy needed
    • Shells & Orbitals
      • The shells can hold:       1st = 2e¯    2nd = 8e¯  3rd =  18e¯ 4th = 32e¯
      • The orbitals
        • S orbital can hold up to 2e¯
        • P orbital can hold up to 6e¯
        • D orbital can hold up to 10e¯
        • F orbital can hold up to 14e¯
      • Filling the shells
        • Energy level 1: 1s
        • Energy lvl2: 2s,2p
        • Energy lvl 3: 3s, 3p, 4s, 3d
        • Energy lvl 4: 4s, 4p, 4d, 4f
    • Chemical Bonding
      • Covalent
        • 2 non-metals, where e- shared
        • Simple Molecuar
          • molecules held together by weak forces but the atoms within molecule held together by strong covalent forces
          • Low MP&BP, do NOT conduct electricity and are soluble in NON-POLAR solvents (b/c vdw form)
        • Giant covalent lattices
          • High MP&BP b/c strong covalent bonds
          • Non-conductors of electricity b/c no free charged particles (except in graphite)
          • Insoluble in both POLAR& NON-POLAR b/c the bonds are too strong to be broken
      • Metallic
        • Occurs in metals bwn all atoms
        • Giant metallic lattice
          • High MP&BP b/c e¯ are free to move. The attraction bwn +ve ions & -ve e¯ is strong. So lot of energy needed to break the bonds
          • Deloclalised e¯ which are able to move throughout the structure. Overall the charge is BALANCED
      • Ionic
        • Metal and non-metal, opposite charges attract
          • The metal becomes a +ve ion and the non-metal a -ve ion
        • Giant ionic lattices
          • Each ion is surrounded by oppositely charged ions which attract to from a lattice
          • High MP&BP so are solid at room temp. This is b/c lot of energy is needed to break strong electrostatic forces holding ions together
            • the greater the charge, the greater the electrostatic attracion
          • When solic annot conduct electricity b/c ions are fixed and cannnot move
          • When solid they cannot conduct elctricty b/c ions are fixed so unable to move
            • when melted or dissolved the lattice breaks down and the ions are free to move so can conduct elctricty
          • Dissolves in POLAR solvent (water) as it breaks down the lattice by surrounding each ion to form a solution
    • Inter molecular (IM) forces
      • V. weak forces bwn small dipoles in diff. molecules
      • Permanent dipole-dipole
        • Polar molecules have permanent dipoles
          • the permanent dipole in a diff. polar molecules from weak permanent dipole-dipole forces
      • van der Waals'
        • exist bwn ALL molecules
          • weak IM attractions bwnv.small temporary dipoles in neighbouring moelcules
        • caused by movement of e¯ in shells, unbalancing the charge distribution
          • the more e¯ the greater the induced dipole, the greater the forces
      • Hydrogen bonding
        • molecules containing OH and NH bonds are polar w/ permanent dipoles
          • These bonds are STRONG dipole-dipole ineractions
        • gives water special properties
          • Ice is less dense thatwater b/c it is an OPEN LATTICE w/ H bonds holding the water mlecules apart
            • when it melts these rigid H bonds collapse and the water moelcules move close togther
  • e.g. for Li there are 3 valence e¯
    • Li = Li+ + e¯ Li+=Li2+ + e¯ Li2+=Li3++e¯
  • Ice is less dense thatwater b/c it is an OPEN LATTICE w/ H bonds holding the water mlecules apart
    • when it melts these rigid H bonds collapse and the water moelcules move close togther

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