Chemistry · Chemical Bonding · NEET
NCERT lists exactly four. (1) The number of hybrid orbitals is equal to the number of atomic orbitals that get hybridised. (2) The hybrid orbitals are always equivalent in energy and shape. (3) Hybrid orbitals are more effective in forming stable bonds than pure atomic orbitals. (4) Hybrid orbitals point in preferred directions to keep minimum repulsion between electron pairs, so the type of hybridisation tells you the geometry of the molecule. Learn these four lines word for word for NEET assertion-reason questions.
NCERT gives four 'important conditions'. (i) Only orbitals of the valence shell of the atom take part. (ii) The orbitals that mix must have almost equal energy. (iii) Promotion (excitation) of an electron is NOT an essential condition before hybridisation. (iv) It is not necessary that only half-filled orbitals mix; in some cases even completely filled valence-shell orbitals can take part. Points (iii) and (iv) are the ones NEET loves to test as tricky statements.
No. This is a very common trap. NCERT clearly states promotion of an electron is NOT an essential condition prior to hybridisation. In many molecules an electron is promoted first (like C going from 2s2 2p2 to one 2s and three 2p singly filled), but that promotion is not a rule for hybridisation itself. So if a statement says 'excitation is compulsory for hybridisation', it is FALSE.
No. Another trap. NCERT says it is not necessary that only half-filled orbitals participate. Even completely filled orbitals of the valence shell can take part. Example: in NH3 and H2O the central atom uses filled orbitals holding lone pairs, and those are still counted in the hybridisation. So lone pairs count when you decide the hybridisation.
Count the number of atomic orbitals that mix, because number of hybrid orbitals formed = number of atomic orbitals mixed. A simple exam shortcut: number of hybrid orbitals = (number of sigma bonds on the central atom) + (number of lone pairs on the central atom). Example: NH4+ has 4 sigma bonds and 0 lone pairs = 4 orbitals = sp3. NO2+ has 2 sigma and 0 lone pairs = 2 = sp. Pi bonds are NOT counted.
Because hybrid orbitals are directed in space to keep electron pairs as far apart as possible (minimum repulsion). Each type has a fixed set of directions: sp is linear (180 degrees), sp2 is trigonal planar (120 degrees), sp3 is tetrahedral (109.5 degrees). So once you know the hybridisation you know the basic arrangement, and lone pairs then bend the final shape. That is why NCERT point 4 links hybridisation to geometry.
Not exactly the same, but almost equal energy. That is why an s and a p orbital of the SAME shell (like 2s and 2p) can mix, but a 2s and a 3p normally do not, because their energy gap is too large. The definition itself says 'intermixing of orbitals of slightly different energies' to give a new set of equivalent orbitals.
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.
Hybridisation is the process of intermixing of atomic orbitals of slightly different energies in the same atom to redistribute their energy and form a new set of orbitals of equivalent energy and shape, called hybrid orbitals. Pauling introduced this idea to explain molecular shapes like CH4, NH3 and H2O.
Salient features describe the properties of the hybrid orbitals that form (equal number, equal energy, stronger bonds, fixed direction giving geometry). Conditions describe when hybridisation can happen (valence-shell orbitals, almost equal energy, promotion not essential, filled orbitals allowed). Features = results; conditions = requirements.
Hybrid orbitals are used in bond formation, not the pure atomic orbitals. NCERT states that unlike pure orbitals, hybrid orbitals form more stable and stronger bonds because they overlap more effectively.
No. The number of hybrid orbitals formed is always equal to the number of atomic orbitals mixed. Mixing one s and three p orbitals gives four sp3 hybrid orbitals, not more or fewer.
The hybrid orbitals point in directions of minimum repulsion, so each hybridisation gives a fixed geometry: sp is linear, sp2 is trigonal planar, sp3 is tetrahedral, sp3d is trigonal bipyramidal, sp3d2 is octahedral. This is one of the most tested links in Chemical Bonding.
