The electrons are arranged symmetrically in the hybridized form which makes carbon able to react but reasonably stable.
In the ground state the electron configuration is
In this state Carbon is more reactive and less stable. In the ground state Carbon forms Carbon monoxide a poisonous gas which reacts strongly with the hemoglobin in the blood forming a strong bond that does not release.
In the hybridized state the electron configuration is
In the more common hybridized form carbon is less reactive and more stable. In the hybridized state Carbon forms Carbon Dioxide.
This gas does not react strongly with the hemoglobin in the blood.
The Carbon dioxide gas is easily released from the hemoglobin in the lungs allowing Oxygen gas to react with the hemoglobin.