Orbital Hybridization Reference Cheat Sheet

A printable reference covering $sp$, $sp^2$, $sp^3$, $sp^3d$, $sp^3d^2$ hybridization, geometry, bond angles, and sigma and pi bonds for grades 10-12.

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Orbital hybridization explains how atomic orbitals mix to form new orbitals used in bonding. This cheat sheet helps students connect electron domains, molecular shape, bond angles, and examples. It is especially useful when predicting structures from Lewis diagrams and VSEPR theory. A clear reference makes it easier to move from a drawing to a three-dimensional molecule.

Key Facts

A steric number of $2$ gives $sp$ hybridization, a linear electron geometry, and a bond angle of $180^\circ$ .
A steric number of $3$ gives $sp^2$ hybridization, a trigonal planar electron geometry, and ideal bond angles of $120^\circ$ .
A steric number of $4$ gives $sp^3$ hybridization, a tetrahedral electron geometry, and an ideal bond angle of $109.5^\circ$ .
A steric number of $5$ gives $sp^3d$ hybridization and a trigonal bipyramidal electron geometry with angles of $90^\circ$ , $120^\circ$ , and $180^\circ$ .
A steric number of $6$ gives $sp^3d^2$ hybridization, an octahedral electron geometry, and bond angles of $90^\circ$ and $180^\circ$ .
The steric number is calculated as $\text{steric number} = \text{number of sigma bonds} + \text{number of lone pairs}$ on the central atom.
A single bond contains $1$ sigma bond, a double bond contains $1$ sigma bond and $1$ pi bond, and a triple bond contains $1$ sigma bond and $2$ pi bonds.
Pi bonds form from unhybridized orbitals, so atoms involved in multiple bonds must keep at least one unhybridized $p$ orbital available.

Vocabulary

Hybridization: Hybridization is the mixing of atomic orbitals to form new orbitals with shapes and energies suited for bonding.
Steric number: Steric number is the total number of sigma bonds and lone pairs attached to a central atom.
Sigma bond: A sigma bond is a covalent bond formed by end-to-end orbital overlap along the line connecting two nuclei.
Pi bond: A pi bond is a covalent bond formed by side-by-side overlap of unhybridized orbitals above and below the bonding axis.
Electron geometry: Electron geometry describes the arrangement of all electron domains, including bonding pairs and lone pairs, around a central atom.
Molecular geometry: Molecular geometry describes the arrangement of atoms only, so lone pairs affect the shape but are not shown as atoms.

Common Mistakes to Avoid

Counting double or triple bonds as multiple electron domains, which is wrong because any single, double, or triple bond counts as $1$ domain for steric number.
Ignoring lone pairs on the central atom, which gives the wrong hybridization because lone pairs are included in $\text{steric number} = \text{sigma bonds} + \text{lone pairs}$ .
Using molecular geometry instead of electron geometry to choose hybridization, which can confuse shapes like trigonal pyramidal and tetrahedral that both come from $sp^3$ electron geometry.
Forgetting that pi bonds use unhybridized orbitals, which is wrong because hybrid orbitals usually form sigma bonds while remaining $p$ orbitals form pi bonds.
Assuming all bond angles are ideal, which is wrong because lone pairs and multiple bonds can compress or expand angles from values such as $109.5^\circ$ or $120^\circ$ .

Practice Questions

1 A central atom has $2$ sigma bonds and $0$ lone pairs. Find its steric number, hybridization, electron geometry, and ideal bond angle.
2 In $\mathrm{NH_3}$ , nitrogen has $3$ sigma bonds and $1$ lone pair. What is the steric number and hybridization of nitrogen?
3 For carbon dioxide, $\mathrm{CO_2}$ , determine the hybridization of the central carbon and count the total number of sigma and pi bonds in the molecule.
4 Explain why the central atom in $\mathrm{CH_4}$ and the central atom in $\mathrm{NH_3}$ have the same hybridization but different molecular geometries.

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