chapter 5 - electron structure

• shells are regarded as energy levels

  the energy increases as the shell number increases

  the shell number or energy level number is called the principal quantum number n
• an atomic orbital is a region around the nucleus that can hold up to two electrons with opposite spins
• s-orbitals

  each shell from n=1 contains one s-orbital

  
• p-orbitals

  each shell from n=2 contains 3 p-orbitals

  
• each shell from n = 3 contain 5 d-orbitals
• each shell from n=4 contains 7 f-orbitals
• order of filling orbitals in n=2

  2s 2p
• order of filling orbitals in n=3

  3s 3p 3d
• order of filling shells in n=4

  4s 4p 4d 4f
• the 3d subshell is at a higher energy level than the 4s sub shell

  the 4s sub shell fills up before the 3d sub shell
• electrons are negatively charged and repel one another
• two electrons in an orbital have opposite spins, which help counteract the repulsion between them
• orbitals are occupied singly first
• positive ions are cations

  negative ions are anions
• nickel element has electron figuration 1s2 2s2 2p6 3s2 3p6 3d8
• ionic bonding is the electrostatic attraction between positive and negative ions
• properties of giant ionic lattices

  • high melting and boiling points - strong electrostatic forces of attraction between oppositely charged ions (the bigger the charge, the higher the melting points)
  • ionic compounds dissolved in polar solvents (solubility decreases as the ionic charge increases)
  • when solid - does not conduct electricity
• ionic compounds in solid state - ions are fixed, there are no mobile charge carriers
• ionic compounds in liquid state - solid ionic lattice breaks down, ions are free to move as mobile charge carriers
• covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
• a covalent bond is the overlap of orbitals, the attraction is localised acting only on the two atoms
• in covalent bonding electrons are shared

  in ionic bonding electrons are transferred
• phosphorus forms PF3 or PF5
• sulfur forms SF2 SF4 SF6
• chlorine forms ClF ClF3 ClF5 ClF7
• a dative covalent bond or a coordinate bond is a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only
• the larger the average bond enthalpy, the stronger the covalent bond