Final answer:
An sp hybridized carbon atom has two valence electrons in sp orbitals and two in unhybridized p orbitals, which participate in forming sigma and pi bonds respectively.
Step-by-step explanation:
A carbon atom that is sp hybridized will have two valence electrons occupying sp orbitals and two valence electrons occupying p orbitals. In sp hybridization, a carbon atom mixes one s orbital with one p orbital to form two sp hybrid orbitals, each holding one electron. These sp orbitals are linearly arranged at 180° from each other.
The remaining two unhybridized p orbitals stay at right angles to the sp orbitals and to each other, each capable of holding one electron, contributing to the formation of pi (π) bonds in molecules like acetylene (H-C≡C-H), where the sp orbitals form sigma (σ) bonds with hydrogen atoms and the unhybridized p orbitals overlap side by side to create π bonds, thus completing the triple bond between carbon atoms.