Electron Configuration & Orbital Diagrams Chemistry Mrs. Stoops

The Rules Hund’s rule – each orbital will fill up with one electron before doubling up – like a bus, people will fill empty seats before sitting with someone Aufbau principle – electrons will occupy the lowest energy level possible – like people, we will do minimal work (not work ahead) or like a ladder, we start at the bottom and work up.

Electron Configurations N = 1s 2 2s 2 2p 3 List all the elements passed through starting from hydrogen down to the element you are looking for Adding up the exponents will equal the atomic number Uses the first two quantum number (row or section letter) Co = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7 ** still subtract for rows Pt = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 8 PT

Exceptions EXCEPTION group: Cr column and Cu column: Cr, Mo, W, Sg, Cu, Ag, Au, Uuu Applies to both orbital and e configurations These elements are “thieves” they steal an electron from the closest “s” section to fill or half-fill the “d” section for stability. Cr = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 PT

Short Cut – Noble Gas Configuration Uses He, Ne, Ar, Kr, Xe, or Rn Find your element. Go back to noble gas last passed through Put the symbol of the noble gas in brackets Continue on from noble gas like normal I = [Kr]5s 2 4d 10 5p 5 Am = [Rn]7s 2 5f 7 PT

Orbital Diagrams Notes Just like electron configurations No short cut Start at hydrogen and continue to the element assigned

Orbital Diagrams How to do orbitals: Draw lines according to the sections: s=1, p=3, d=5, f=7 Must draw all the lines Arrows are the exponents (electrons) Fill the lines for each section with the exponent number. N = 1s 2 2s 2 2p 3 N =      1s 2 2s 2 2p 3 Cr = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 Cr =       1s 2 2s 2 2p 6 3s 2          3p 6 4s 1 3d 5 PT

Back to: E config exceptions Short-cut orbitals