Hybridisation of the third carbon in CH3-CH2-CH2(-)

The hybridisation of an atom is determined by its electron configuration, which in turn is determined by the number of electrons present in the atom's valence shell. In the case of the third carbon in CH3-CH2-CH2(-), the electron configuration is as follows:

- Carbon atoms have four valence electrons.
- The carbon atoms in CH3-CH2-CH2(-) are bonded to other atoms or groups of atoms, with each bond representing two electrons.
- The third carbon atom is bonded to two other carbon atoms and one hydrogen atom, with one lone pair of electrons on the carbon atom.

Determining hybridisation

To determine the hybridisation of the third carbon atom, we need to count the number of electron groups around it. An electron group can be a bond or a lone pair of electrons. In this case, the third carbon atom has three electron groups:

- Two carbon atoms bonded to it
- One hydrogen atom bonded to it
- One lone pair of electrons on it

The hybridisation of an atom with three electron groups is sp2. This means that the third carbon atom in CH3-CH2-CH2(-) has sp2 hybridisation.

Conclusion

The hybridisation of the third carbon atom in CH3-CH2-CH2(-) is sp2. This is because the carbon atom has three electron groups around it, consisting of two carbon atoms, one hydrogen atom, and one lone pair of electrons. The sp2 hybridisation allows the carbon atom to form three sigma bonds with its neighbours, as well as one pi bond with the neighbouring carbon atom.