electron configuration

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  • electron configuration
    • 1s2, 2s2,2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 4d10
      • lowest energy sub-shells filled first
      • 4s sub shell filled before 3d because it has lower energy
    • an orbital can hold two electrons, one goes clockwise, one goes anticlockwise
    • Bus rule
    • ionisation energies
      • 1st  IE is the amount of energy required to remove 1 mol of electrons from 1 mol of a gaseous atom
        • the lower the IE the easier is is to form an ion
        • X(ne1)+ (g) -> Xn+(g) + e-
      • factors affecting IE
        • atomic radius: less attraction between e- and nucleus; less energy needed to remove e-; smaller iE
        • charge on nucleus: more protons; more charge; more energy needed to remove e-; larger IE
        • shielding: more shells; more shielding; less energy needed to remove e-; smaller IE
      • successive ionisation is the energy needed to remove 1e- from each ion in one mol of gaseous 1+ ions to form 1 mol gaseous 2+ ions
      • trends
        • ionisation increases across period 3
          • protons increase; atomic radius decreases; shielding stays the same
          • anomalies: Al and S
            • Al: Al outer e- in 3p orbital which is further from nucleus than 3s; 3p shielded by 3s
            • S: sheilding  is the same; in P e- is being removed from singly occupied orbital whereas in S there's 2 e- in orbital; repulsion
            • evidence for sub-shells
        • ionisation decreases down the group
          • more shielding; atomic radius increases
  • ionisation decreases down the group
    • more shielding; atomic radius increases

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