Hybridization is bookkeeping for geometry: an atom mixes its valence orbitals into a matched set that points where the molecule needs — so you count instead of memorize.
One carbon, three hybridizations — more bonds packed in means a straighter, tighter geometry. Drawn live.
1. Count the Groups Around an Atom to Get Its Hybridization
Add up an atom's σ bonds and lone pairs — the total is the number of orbitals mixed, and it names the hybrid: 4 → sp³, 3 → sp², 2 → sp.
2. sp³ Is Tetrahedral (109.5°), sp² Is Trigonal Planar (120°), sp Is Linear (180°)
Groups spread as far apart as possible, so geometry falls straight out of the count — fewer groups means a straighter shape (lone pairs squeeze angles a little, as in water's 104.5°).
3. Hybrid Orbitals Make σ Bonds; Leftover p Orbitals Make π Bonds
σ bonds and lone pairs live in hybrid orbitals (what you count); π bonds are built from leftover p orbitals — one on sp² (one π), two on sp (two π) — which is why they never count.
4. Heteroatoms Count the Same Way — Just Remember the Lone Pairs
Oxygen and nitrogen follow the same recipe once you include lone pairs: water's O (2 σ + 2 lp) and ammonia's N (3 σ + 1 lp) are both sp³; a nitrile C and N are both sp.
5. More s-Character Means Shorter, Stronger Bonds and More Stable Anions
s-character rises sp³ (25%) → sp² (33%) → sp (50%), pulling electrons closer to the nucleus, so bonds get shorter and stronger and anions more stable — which is why a terminal alkyne C–H is the most acidic.
Want the full argument behind that acidity trend? See the acidity of terminal alkynes.
6. Summary
Count σ bonds + lone pairs, ignore π · 4 → sp³, tetrahedral, 109.5° · 3 → sp², trigonal, 120°, one π · 2 → sp, linear, 180°, two π · hybrids hold σ + lone pairs, leftover p holds π · s-character rises sp³→sp, so bonds shorten and anions stabilize.
Quiz yourself
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The oxygen has 2 σ bonds + 2 lone pairs = 4 groups → sp³. It is bent, and the angle compresses to ~104.5° because the two lone pairs push harder than bonding pairs, squeezing the H–O–H angle below the ideal tetrahedral 109.5°.
You count groups (σ bonds + lone pairs), not total bonds. The alkyne carbon has just 2 σ bonds (one to carbon, one to H or R) and no lone pairs → 2 groups → sp, linear at 180°. The other two bonds of the triple bond are π bonds made from its two leftover p orbitals.
One σ + one π. The σ bond is made from an sp² hybrid orbital on each atom; the π bond is made from the leftover unhybridized p orbital on each atom overlapping side-on above and below the plane.
An sp orbital has 50% s-character versus 25% for sp³. Removing the proton leaves the lone pair in an sp orbital that sits closer to the nucleus, so the resulting carbanion is more stable — and a more stable conjugate base means a stronger (more acidic) parent. Higher s-character = more stable anion = more acidic.
Draw this on the whiteboard
Open the OChem Board whiteboard — benzene rings, wedge/dash bonds, and a clickable periodic table built in. No account needed.