How do you determine sp sp2 and sp3 orbitals?

1 Answer
David Drayer
Sep 7, 2016

Look at the number of valance electrons.
If there are 3 valance electrons it will be #sp^2#
If there are 4 valance electrons it will be #sp^3#

Explanation:

Paired electrons typically do not form chemical bonds. (Paired electrons do form intermolecular bonds)
So the paired s electrons gain a little energy to jump into open p orbitals in order to form chemical bonds. The gain in ethalpy is balanced by stability gained by forming chemical bonds.

In Aluminium #Al_13^27# the ground state electron structure is
#1s^2 2s^2 2p^1# In the ground state Aluminum can form only 1 bond but by hybridizing the s orbital with 2 p orbital Aluminum can form three chemical bonds #(Al^+3)# . At +3 Aluminum is very stable having obtained the noble gas structure of Neon.

In Carbon #C_6^12# the ground state electron structure is
#1s^2 2s^2 2p^2# This leaves one p orbital open. In ground state Carbon can only form 2 bonds as in Carbon Monoxide. CO.
By hybridizing the 1 s and 3 p orbitals, Carbon can form 4 bonds. as in #CO_2#

So if there are only three valance electrons it is #sp^2#
If there are four valance electrons it is #sp^3#

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