Chem Ch. 8 & 9

Bonds

• Double bonds are shorter & stronger than single

• Triple bonds are shorter & stronger than double

Formal charge

(number of valence electrons in an isolated atom) - (the number of valence electrons assigned to atom)

Exceptions to Lewis structure

• Odd # of electrons does not form complete octets like NO molecule

• BeCl and BF make less than an octet

• P-block elements in row 3 or below can have more than an octet like PCl5 and XeF4

Lattice energy

higher charge requires greater lattice energy to separate, smaller ions require more energy to separate

Electronegativity

• Increases across a row & up a group

• Fluorine is most electronegative

• C & H have similar electronegativities so they have no diploes

Polar

a bond that has a dipole

Nonpolar

a bond that does not have a dipole

VSEPR Theory

• 1 single bond= 1 domain

• 1 lone pair= 1 domain

• 1 double bond= 1 domain

• 1 triple bond= 1 domain

2 electron domain geometry

• linear

• 180 degrees

3 electron domain geometry

• trigonal planar

• 120 degrees

4 electron domain geometry

• tetrahedral

• 109.5 degrees

5 electron domain geometry

• trigonal bipyramidal

• 120; 90 degrees

6 electron domain geometry

• octahedral

• 90 degrees

trigonal planar molecular shape

• trigonal planar (no lone pairs)

• Bent (1 lone pair)

tetrahedral molecular shape

• tetrahedral (no lone pairs)

• trigonal pyramidal (1 lone pair)

• bent (2 lone pairs)

trigonal bipyramidal molecular shape

• trigonal bipyramidal (no lone pairs)

• seesaw (1 lone pair)

• T-shaped (2 lone pairs)

• linear (3 lone pairs)

octahedral molecular shape

• octahedral (no lone pairs)

• square pyramidal (1 lone pair)

• square planar (2 lone pairs)

• T-shaped (3 lone pairs)

• linear (4 lone pairs)
  

angles

• double and triple bonds slightly increase angle

• lone pairs decrease angle by a few degrees

2 electron domains hybridization

sp, linear

3 electron domains hybridization

sp², trigonal planar

4 electron domains hybridization

sp³, tetrahedral

5 electron domains hybridization

sp³d, trigonal bipyramidal

6 electron domains hybridization

sp³d², octahedral

sp

• 2 hybrid orbitals

• 2 unhybridized p orbitals

sp²

• 3 hybrid orbitals

• 1 unhybridized p orbital

sp³

• 4 hybrid orbitals

• 0 unhybridized

bond order = 0

no bonds form

bond order > 0

molecule is stable

• 1 bond order = single

• 2 bond order = double

• 3 bond order = triple

double bond

one sigma and one pie bond

triple bond

one sigma and two pie bonds

paramagnetic

molecules with unpaired electrons

diamagnetic

molecules with paired electrons