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s and p Bonds MO Theory

s and p Bonds MO Theory. MO Theory: s orbitals. s orbitals form s and s * molecular orbitals Add and subtract orbitals to get the bonding and anti-bonding orbitals Start with 2 atomic s orbitals end with 2 molecular orbitals.

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s and p Bonds MO Theory

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  1. s and p BondsMO Theory

  2. MO Theory: s orbitals • s orbitals form s and s* molecular orbitals • Add and subtract orbitals to get the bonding and anti-bonding orbitals • Start with 2 atomic s orbitals end with 2 molecular orbitals. • Fill in electrons from low to high energy, just like in atomic orbital diagrams 1s-1s Anti-bonding MO, σ*1s E isolated H atoms 1s+1s Bonding MO, σ1s

  3. MO Theory: p orbitals • p orbitals form sand s* molecular orbitals or p and p* orbitals depending on type of overlap • Add and subtract orbitals to get the bonding and anti-bonding orbitals • Start with 6 atomic orbitals end with 6 molecular orbitals • Fill in electrons from low to high energy, just like in atomic orbital diagrams End to end overlap Side to side overlap

  4. Practice • The ground-state electron configuration of the ion C2n- is s2s2s2s*2p2p4s2p2. • What is the charge on the anion? • Draw the MO diagram. • Is it paramagnetic or diamagnetic? • What is the bond order? • Hint: ½(bonding electron-antibonding electrons) • Would adding an electron add or subtract from the bond order? • Would subtracting an electron make the bond longer or shorter?

  5. Heteronuclear Practice • For CN the energy of the molecular orbitals follows the order of carbon (a.k.a. p2p<s2p) • Draw the MO diagram. • Give the valence shell electron configurations of CN and CN-. • Are they paramagnetic or diamagnetic? • Tell the bond order of each. • Which has the stronger bond?

  6. Practice • Consider the hypothetical species HeH. What charge, if any, should be present on this combination of atoms to produce the most stable molecule or ion possible? • Draw the MO diagram for the neutral species first. • Decide what ion gives largest bond order • What is the bond order on the neutral species and what bond order, if changed, is on the ion you chose? • If the charge on the neutral species were increased or decreased by one what would be the affect on the bonding of the atom. • If the charge on the species you chose were increased or decreased by one what would be the affect on the bonding of the atom.

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