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What is sp2 Hybridisation (Basic)?
Grade Level:
Class 10
AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine
Definition
What is it?
sp2 hybridisation is when one 's' atomic orbital and two 'p' atomic orbitals mix together to form three new, identical hybrid orbitals. These new hybrid orbitals are called sp2 hybrid orbitals and arrange themselves in a flat, triangular shape around the central atom.
Simple Example
Quick Example
Imagine you have three different types of sweets: one ladoo (s-orbital) and two jalebis (p-orbitals). When you mix them all up and reshape them, you don't get individual ladoos and jalebis anymore. Instead, you get three completely new, identical sweets – let's call them 'sp2 mithai' – that are a mix of both. These three 'sp2 mithai' will then arrange themselves neatly in a triangle on a plate.
Worked Example
Step-by-Step
Let's look at how sp2 hybridisation happens in an ethene molecule (C2H4), where each carbon atom is sp2 hybridised.
Step 1: Consider a carbon atom in its ground state. Its electron configuration is 1s^2 2s^2 2p^2. This means it has 2 electrons in the 2s orbital and 2 electrons in the 2p orbitals (one in 2px, one in 2py, and 2pz is empty).
---Step 2: For bonding, one electron from the 2s orbital is promoted to the empty 2pz orbital. Now the excited carbon atom has 1 electron in 2s, 1 electron in 2px, 1 electron in 2py, and 1 electron in 2pz.
---Step 3: The one 2s orbital and two 2p orbitals (2px and 2py) mix together. The 2pz orbital remains unhybridised.
---Step 4: This mixing forms three new, identical sp2 hybrid orbitals. These three sp2 orbitals are arranged in a trigonal planar (flat triangle) geometry around the carbon atom, with bond angles of 120 degrees.
---Step 5: The unhybridised 2pz orbital remains perpendicular to the plane of the sp2 hybrid orbitals.
---Step 6: Each carbon atom uses two of its sp2 orbitals to bond with two hydrogen atoms (forming C-H sigma bonds) and one sp2 orbital to form a sigma bond with the other carbon atom (C-C sigma bond).
---Step 7: The unhybridised 2pz orbital on each carbon atom then overlaps sideways to form a pi bond between the two carbon atoms. This results in the double bond in ethene.
---Answer: Each carbon atom in ethene forms three sp2 hybrid orbitals, leading to a trigonal planar geometry around each carbon and forming a C=C double bond.
Why It Matters
Understanding sp2 hybridisation is crucial for designing new materials in Biotechnology and Engineering, like plastics or medicines. It helps chemists predict the shapes of molecules, which is vital for developing new drugs in Medicine or creating advanced materials for Space Technology.
Common Mistakes
MISTAKE: Thinking all 'p' orbitals participate in sp2 hybridisation. | CORRECTION: Only two 'p' orbitals (e.g., px and py) mix with the 's' orbital. One 'p' orbital (e.g., pz) remains unhybridised and forms a pi bond.
MISTAKE: Believing sp2 hybridisation results in a linear or tetrahedral shape. | CORRECTION: sp2 hybridisation always leads to a trigonal planar (flat triangular) geometry with bond angles of 120 degrees.
MISTAKE: Confusing hybrid orbitals with atomic orbitals. | CORRECTION: Hybrid orbitals are new orbitals formed by mixing atomic orbitals; they are not the original 's' or 'p' orbitals.
Practice Questions
Try It Yourself
QUESTION: How many sp2 hybrid orbitals are formed when one 's' and two 'p' orbitals mix? | ANSWER: Three sp2 hybrid orbitals are formed.
QUESTION: What is the approximate bond angle in molecules where the central atom is sp2 hybridised? | ANSWER: The approximate bond angle is 120 degrees.
QUESTION: If a central atom forms three sigma bonds and has no lone pairs, what type of hybridisation is it likely to undergo? Explain your reasoning. | ANSWER: It is likely to undergo sp2 hybridisation. This is because sp2 hybridisation forms three hybrid orbitals, which are perfect for accommodating three sigma bonds and result in a trigonal planar geometry.
MCQ
Quick Quiz
Which of the following molecules has a central carbon atom that is sp2 hybridised?
Methane (CH4)
Ethene (C2H4)
Ethane (C2H6)
Ethyne (C2H2)
The Correct Answer Is:
B
Ethene (C2H4) contains a carbon-carbon double bond. Each carbon atom in a double bond is sp2 hybridised. Methane and Ethane have sp3 hybridised carbons, while Ethyne has sp hybridised carbons.
Real World Connection
In the Real World
sp2 hybridisation is key to understanding the structure of graphene, a super-strong, super-light material used in advanced electronics and future mobile phone screens. It's also found in plastics like PVC (though PVC also has sp3 carbons), which are used in pipes and everyday items all around us in India.
Key Vocabulary
Key Terms
Hybridisation: The mixing of atomic orbitals to form new, identical hybrid orbitals. | Atomic Orbital: A region around the nucleus where an electron is likely to be found. | Sigma Bond: A strong single bond formed by direct overlap of orbitals. | Pi Bond: A weaker bond formed by sideways overlap of p-orbitals. | Trigonal Planar: A flat triangular molecular geometry.
What's Next
What to Learn Next
Next, explore 'What is sp Hybridisation?' and 'What is sp3 Hybridisation?'. These concepts will show you how different combinations of atomic orbitals lead to various molecular shapes and properties, helping you understand the amazing diversity of chemical compounds.
