CBSE Class 9 Answered

can u plz provide me a study material or give me d study basis of the concept of orbital overlapping and sigma and pi bond formation!!!and s-s,s-p,p-p orbital overlapping and the formation of hybrid orbitals like sp3,sp2,sp etc??

Asked by | 09 Dec, 2012, 01:56: PM

Expert Answer

Hydrogen molecule consists of two H-atoms. Each atom contains one electron in 1s-orbital. E.C = 1s¹

According to molecular orbital theory two 1s¹ orbitals of two H-atoms overlap linearly to produce two types of molecular orbitals.
1. Bonding molecular orbital (s-orbital)
2. Anti-bonding molecular orbital (s^*-orbital)
Bonding molecular orbital (s-orbital) has lower energy and results in the covalent bond formation which is a sigma bond between two H-atoms while the anti-bonding molecular orbital (s^*-orbital) possess high energy remains unoccupied.

s-p type overlap occurs in HF molecule when one 1s-orbital of hydrogen atom overlaps 2p-orbital of fluorine to form two types of molecular orbitals.
1. Bonding molecular orbital (s-orbital)
2. Anti-bonding molecular orbital (s^*-orbital)
Bonding molecular orbital (s-orbital) has lower energy and results in the covalent bond formation (sigma bond) between H-atom and F-atom while the anti-bonding molecular orbital (s^*-orbital) possess high energy remains unoccupied.

Another kind of hybridization uses the s orbital and two of the p orbitals from the second energy level of carbon to form three hybrid orbitals. This kind of hybridization is called sp² hybridization. It has three hybrid orbitals and there is also an unchanged p orbital that is not shown here. The geometric arrangement of these three sp² hybrid orbitals is in a flat plane with 120 degree angles between them. The leftover p orbital lies at a 90 degree angle to the hybrid orbitals. If it had been included in this diagram, its two lobes would be pointing directly at and away from you. This kind of hybridization occurs when a carbon atom is bonded to three other atoms. If it is a very simple molecule with just the carbon atom and the other three atoms, it would be a flat triangular molecule. If this is part of a larger molecule, this part would have a flat triangular shape.

There is still a third type of hybridization, it is sp hybridization. In it the s orbital and one of the p orbitals from carbon's second energy level are combined together to make two hybrid orbitals. Those hybrid orbitals form a straight line. There is a 180 degree angle between one orbital and the other orbital. They are exactly opposite one another from the center of the carbon atom. Because this type of sp hybridization only uses one of the p orbitals, there are still two p orbitals left which the carbon can use. Those p orbitals are at right angles to one another and to the line formed by the hybrid orbitals. If they were shown in this diagram, one would go straight up and down and the other would go straight toward and away from you. This kind of hybridization occurs when a carbon atom is bonded to two other atoms.

sp³ hybridization results from the combination of the s orbital and all three p orbitals in the second energy level of carbon. It results in four hybrid orbitals and occurs when a carbon atom is bonded to four other atoms. The geometric arrangement of those four hybrid orbitals is called tetrahedral.

p-p type overlap occurs in F₂ molecule when one 2p_z-orbital of one fluorine atom overlaps 2p_z-orbital of other fluorine atom form two types of molecular orbitals.
1. Bonding molecular orbital (s-orbital)
2. Anti-bonding molecular orbital (s^*-orbital)
Bonding molecular orbital (s-orbital) has lower energy and results in the covalent bond formation (sigma bond) between two F-atoms while the anti-bonding molecular orbital (s^*-orbital) possess high energy remains unoccupied.

Answered by | 10 Dec, 2012, 11:05: AM