this theory states that bonding pairs of electrons arrange themselves as far as possible from each other to minimise repulsion
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assumptions of EPR
1)the shape of the molecule depends on the number of electron pairs around the central atom 2)electrons repel each other and arrange themselves far apart
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formulas
domains=bond pairs + lone pairs lone pairs=group number - bond pairs
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determining polar and non-polar molecules
*polar molecules FONCl (bonds) , unsymmetric molecule NOTE;Symmetric molecules are non-polar since the dipoles cancel out each other
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lone pairs and polar molecules
nh3 107 degrees.It is unsymmetric hence dipoles reinforce each other (3 bond pairs one lone pair) N/B;A LONE PAIR MAKES A MOLECULE UNSYMMETRIC THEREFORE POLAR.A LONE PAIR REDUCES BOND ANGLE BY 2.5 DEGREES
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shapes of ions
For positive ions with a single charge subtract one from the group number then get the domains e.g.NH4+ [domains=LP+BP} bond angle 109.5 (tetrahedral shape).For negative ions add one to the group no.e.g.CH3- is 107 (trigonal pyramidal)
lone-pair lone-pair repulsion is greater than lp-bp and the least is bond pair-bond pair repulsion
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SUMMARY
For a molecule to be polar check 2 things 1)presence of polar bonds FONCl and 2) molecule is unsymmetric Common polar molecules NH3 (107)[Trigonal pyramidal) and H2O (104.5)[V shaped] lone pair makes a molecule unsymmetric therefore polar
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Other cards in this set
Card 2
Front
assumptions of EPR
Back
1)the shape of the molecule depends on the number of electron pairs around the central atom 2)electrons repel each other and arrange themselves far apart
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