Cards (25)

  • Shells:
    • regarded as energy levels
    • energy increases as shell number increases
    • shell number/ energy level = principal quantum number (n)
  • Number of electrons = 2n^2
  • Atomic orbitals —> a region around the nucleus that can hold up to 2 electrons with opposite spins
  • Sub-shell S—> 2 electrons & 1 orbitals
  • Sub shell P —> 6 electrons & 3 orbitals
  • Sub shell d —> 10 electrons & 5 shells
  • sub shell f —> 14 electrons & 7 shells
  • S-orbitals are spherical
  • p-orbitals are dumbbell shaped
  • 3 p-orbitals are arranged on 3 separate axes one along x , one along y and the 3rd along z
  • Filling orbitals:
    • Fill from the lowest energy level available
    • 2 electrons can be in an orbital but must have opposite spin
    • Only pair up electrons if no other orbitals are present
    • electrons repel each other so being in separate orbitals means less repulsion & therefore more stable
  • Half arrows —> are used to represent one electron and to show its direction of spin
  • Copper and chromium are exceptions to the electron configuration
    • 3d sub-shell is more stable when either half full or completely full
  • copper configuration —> 1s2 2s2 2p6 3s2 3p6 3d10 4s1
    chromium configuration —> 1s2 2s2 2p6 3s2 3p6 3d5 4s1
  • When ionising e- lost from 4s sub-shell first
  • Ionic bonding —> electrostatic attraction between positive & negative ions. It holds together cations & anions in ionic compounds
  • Ionic compounds —> metal + non-metal
  • Ionic structure = giant ionic lattice
    • each ion is surrounded by oppositely charged ions, forming a giant ionic lattice
    • solids at room temperature
    • high energy needed to overcome strong, electrostatic attraction between ions
    • high melting and boiling points
    • many ionic compounds dissolve in polar solvents (e.g: water)
    • compounds with large charges —> ionic attraction may be too strong, for water to be able to break down the lattice —> compound will not be very soluble
  • Solubility requires 2 main processes:
    • ionic lattice must be broken down
    • water molecules must attract and surround ions
  • In the solid state:
    • ions are in fixed position in the giant ionic lattice
    • there are no mobile charge carriers
    • non-conductor of electricity in solid state
  • When liquid or dissolved in water:
    • Solid ionic lattice breaks down
    • ions are now free to move as mobile charge carriers
    • is an conductor of electricity in liquid and aqueous states
  • covalent bonding —> strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.
    • covalent bonding occurs between non-metallic elements, compounds of non-metallic elements and polyatomic ions
  • orbital overlap:
    • shared pair of electrons is attracted to the nuclei of both the bonding atoms
    • Bonded atoms often have outer shell with the same electron structure as the nearest noble gas
    • boron, phosphorus, sulfur and chlorine are exceptions —> can bond with more f atoms to have more than 8 electrons in the outer shell
    • In SF6, 6 unpaired electrons from sulfur are paired
    • the outer shell of sulfur now contains 12 electrons, more than the nearest noble gas argon
    • This is called expansion of the octet and is only from the n=3 shell, when a shell becomes available foe the expansion
  • Average bond enthalpy:
    • A measurement of covalent bond strength
    • The larger the value of the average bond enthalpy, the stronger the covalent bond