MC- Molecular Shape Hybridization

Why do molecules adopt specific shapes

VSEPR theory - electrons repel each other

-in ammonia and water there are different bonds,lone pairs and bond angles ( due to the lone pairs repel more than bonded pairs so bonds are close together )

Example : methane

-Methane is tetrahedral

-the four pairs of electrons ,one in each bond are repelling each other

-109 degrees bond angle

-there are 4 identical sigma bonds ( from s orbitals) BUT there isn’t four s orbitals there is only one

HOW - Hybridization

What is hybridization ?

• atomic orbitals 2s ,2p combine with each other to give four hybridized orbitals 

• each hybridized orbital contains one electron 

• the 2 phases can overlap in phase or out of phase 

• it is  used to explain THEORY what we observe vs wha t we expect to happen 

Describe the type of hybridization in alkanes ( ethane)?

ethane-

• carbons are sp3 hybridized 

• Each forms a sigma (σ) bond with:

    three hydrogen 1s orbitals

    one carbon sp³ hybridised orbital

What is sp3 hybridization?

when the 2s orbital combines with 3  x2p orbitals to give 4 hybridized orbitals 

note- each has ¼ s character and ¾ p character - sp3 = tetrahedrally arranged 

What is the electron configuration of an sp3 hybridized carbon ?

overall energy is the same

-draw sp3 orbital between s and the p

Describe the type of hybridization of carbon in alkenes( Ethene)

• carbon has sp2 hybridization

• Three sigma (σ) bonds with:

    -two hydrogen 1s orbitals

    -one carbon – carbon  hybridised orbital

    -requires 3 hybridised orbitals:

    Uses 2p_x, 2p_y orbitals

    Each has 1/3 s character and 2/3 p character – sp²

    Trigonally arranged - all in one plane because of x,y

note - 2pz left unchanged as a p orbital forms a Pi bond ( double bond)

What is sp2 hybridization  ?

• when 1× 2s orbital combine with 2× 2p orbital 

• you use the 2px,2py orbital 

• 2pz used to from pi ( double bond)

• each has 1/3s character  and 2/3 p character - sp2 

• arranged trigonally  

note- this is for all carbon carbon double bonds 

Describe the hybridization in alkyne ( ethyne)

• it has sp hybridization

• it has a triple bond

• Two sigma (σ) bonds with:

    -one hydrogen 1s orbitals

    -one carbon hybridized orbital

   - requires 2 hybridized orbitals

    -Uses 2p_z orbital

   - Each has ½ s character and ½ p character – sp

    ^-Linearly arranged

  2p_x, 2p_y are left unchanged as p orbitals and form the π bonds

What is sp hybridization ?

-Happens when there is a triple bond

• 2s orbital combines with a p ( z ) orbital

• each has ½ character and ½ character

• arranged linearly

What is the electron configuration of sp ?

What are the possible oxygen hybridization?

• oxygen has six electrons in its valence shell 

• it depends on the molecules 

types :

• sp3 hybridization- four hybridized orbitals ,two contains 2 electrons

• sp2 hybridization - three hybridized orbitals ,two contain 2 electrons,one remaining  p orbitals to form  Pi orbitals  

note- the lone pairs are in the hybridized orbitals at lower energy 

electron configuration of sp3 hybridized oxygen

electron configuration of sp2 hybridized oxygen

carbonyl groups - hybridized orbitals

the carbon :

-Three sigma bonds

 - two hydrogen 1s orbitals

  -one oxygen hybridized orbital

  -sp² hybridised

the oxygen :

-one sigma bond – overlap of sp² hybridized orbitals

  -one pi bond – overlap of p orbitals

 - lone pairs are in non bonding hybrid orbitals