ICHEM PT2 (Quantum #, e- config(principle), periodic trends

• Hund's rule states that every orbital should be singly occupied first before it can have 2 e-
• Aufbau principles states that fill the orbital in increasing energy level (from lowest to highest energy level)
• Madelung's rule answers aufbau's principle on how to "build up" the orbitals (from lowest to highest); orbitals with lower n + l value are filled first
• Pauli's Exclusion principle states that:

  1. an orbital must contain only 2 electrons
  2. no 2 e- can have the same set of quantum #s
• allowed electronic transition

  • ∆ml = ±1
  • ∆ms = ±1
• Zeff equation


  Z= Z - S
• Factors that make the 2s e- in gas-phase atoms become nearer to the nucleus

  • valence electron (more VE; e.g. 3s2 3p2 vs 2s2 2p5; n=3)
  • # of protons (Z); (Si vs N)
• Ionization Energy is the energy required to remove electrons from an atom or molecule
• Trend for Ionization Energy

  • L->R: IE increases (since e- are more held together)
  • down a group: IE decrease (e- are farther to nucleus. Hence, less attraction to the nucleus)
• the 8 general periodic trends?

  CMAR & IEEA

  • C (tendency to form a cation)
  • M (Metallic Property)
  • A (atomic size)
  • R (Reactivity)
  • I (ionization energy)
  • E ( e- affinity)
  • E ( electronegativity)
  • A (tendency to form an anion)
• Trend for CMAR

  • L->R: decreasing
  • down a group: increasing
• Trend for IEEA:

  • L->R: Increasing
  • down a group: decreasing
• Is Ionization Energy Endothermic(absorbs heat) or Exothermic(releases heat) process?

  Endothermic process since it requires heat to break the bond (bond breaking)
• Is Electron affinity an endothermic or exothermic process?

  Exothermic process since it is the attraction of electron towards other atom (initiating bond formation which is an exothermic process)
• Lanthanide contraction is the result of poor shielding effect. it is due to scattered/diffused electrons in 4f orbital. Hence, less repulsion and low opposing force to nucleus attraction
• Shielding effect is the electron-electron repulsion of inner and outer shell electrons
• Electronegativity dictates what kind of bond will the atoms be when combined (e.g. NP covalent bond, Polar covalent bond, ionic bond)
• it dictates how strong the e-negativity of the element

  Pauling electronegativity value
• arrange the elements in increasing e- negativity strength: N,O,Br,C,F,H


  F > O > N > Br > C > H
• Pauling e-negativity value table:

  If

  < 0.4 non-polar covalent bond (Non-metal to non metal)

  < 0.4 EN < ~1.7 polar covalent bond (unequal distribution of e- b/w two atoms towards the more e-neg. atom)

  > ~1.7 Ionic bond (metal-nonmetal)
• It is the measure of the nuclear attraction between the nucleus and e-?

  Effective Nuclear charge (Zeff)
• The higher the Zeff, the stronger the force of attraction between the nucleus and the valence e-
• increase in Z eff = increase in e-negativity
• Increasing atomic number means increasing effective nuclear charge which increases the energy required to remove an electron from its orbital.
• Zeff trend

  L-R:

  down a group:

  increasing, decreasing
• # of orbitals formula

  $n^2$
• # of max # of e-?

  $2n^2$
• It is the distance of e- from the nucleus?

  energy level, n
• l

  l= _ -> n-_

  it is equivalent to?

  shape of the orbitals, l=0 to n-1, spdf
• ml

  depends on?

  orientation of the orbital, l (-l or l)
• to locate e- we need to know the?

  l and ml