Chemistry · Chemical Bonding · NEET
The difference is how many orbitals get mixed. sp mixes 1 s + 1 p orbital = 2 hybrid orbitals (linear, 180 degrees). sp2 mixes 1 s + 2 p = 3 hybrid orbitals (trigonal planar, 120 degrees). sp3 mixes 1 s + 3 p = 4 hybrid orbitals (tetrahedral, 109.5 degrees). More p character means the orbitals spread out less, so the bond angle gets smaller: 180 to 120 to 109.5. This matters for NEET because shape and bond angle questions are asked almost every year.
Look at the bonds on that carbon. Single bonds only (like in CH4 or CH3-) means sp3. One double bond (like in CH2=CH-) means sp2. One triple bond or two double bonds (like in HC#C- or O=C=O) means sp. Quick rule: count the number of atoms directly attached plus lone pairs. 4 gives sp3, 3 gives sp2, 2 gives sp. This is the fastest trick for exam speed.
The four sp3 orbitals push away from each other as far as possible in 3D space. The most spread-out arrangement for four directions is a tetrahedron, and the angle between the corners of a perfect tetrahedron is 109.5 degrees, not 90. If they were at 90 degrees they would be too close and repel more, so nature picks 109.5 to lower repulsion. This is the electron-pair repulsion idea (VSEPR).
Yes. Lone pairs on the central atom take up orbital space too, so you must count them. Use: number of sigma bonds + number of lone pairs on the central atom. In NH3, N has 3 sigma bonds + 1 lone pair = 4, so it is sp3. In H2O, O has 2 sigma bonds + 2 lone pairs = 4, so it is also sp3. Only pi bonds are ignored in this count.
Yes. sp means only 2 hybrid orbitals, and 2 directions that push apart the most give a straight line, so the shape is linear with a 180 degree angle. Examples are BeCl2, CO2, C2H2 (acetylene) and the two carbons in a C#C triple bond. If you see a triple bond or two double bonds on one atom, that atom is sp and linear.
The hybridizations of the atomic orbitals of nitrogen in NO2+, NO3- and NH4+ respectively are:
Which of the following molecules represents the order of hybridisation sp2, sp2, sp, sp from left to right atoms?
BF3 is planar and an electron-deficient compound. The hybridization and number of electrons around the central atom, respectively, are:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Add the number of sigma bonds and lone pairs on the central atom. If the total is 2 it is sp, 3 it is sp2, and 4 it is sp3. Ignore pi bonds in this count. This one step answers almost all sp/sp2/sp3 questions quickly in the exam.
sp is 180 degrees (linear), sp2 is 120 degrees (trigonal planar), and sp3 is 109.5 degrees (tetrahedral). The angle gets smaller as the number of hybrid orbitals increases because more orbitals must share the same space.
sp: CO2, BeCl2, acetylene (C2H2). sp2: BF3, ethene (C2H4), NO3-. sp3: CH4, NH3, H2O, NH4+. Learning these standard examples covers most NEET questions on this topic.
Yes, both are sp3 because they have 4 electron regions (bonds + lone pairs). NH3 has 3 bonds + 1 lone pair and H2O has 2 bonds + 2 lone pairs. Lone pairs push harder, so the visible shapes are pyramidal and bent, but the hybridisation is still sp3.
It directly decides molecular shape and bond angle, and it appears in matching questions and predicting geometry almost every year. If you can find hybridisation fast, you can answer many bonding questions in seconds, which saves time for harder problems.
