Molecular Geometry Calculator
VSEPR shape, hybridization, bond angle and polarity, plus formal charge.
Steric number = bonded atoms + lone pairs. Formal charge = valence electrons − nonbonding electrons − bonds (each bond counts once, whatever its order).
Molecular geometry
Tetrahedral
Steric number
4
Hybridization
sp³
Typical bond angle
109.5°
Polarity
Polar
Learn more
What it does
Molecular geometry explains why molecules with the same formula behave differently: shape sets polarity, and polarity sets solubility, boiling point and reactivity. VSEPR predicts that shape from a single count of electron domains, which makes it the fastest structural estimate available before a quantum calculation. Hybridization follows the same count, and formal charge adds the electron bookkeeping needed to judge which Lewis structure is the most reasonable.
When to use it
Use the VSEPR mode to check the shape and hybridization of a molecule before drawing it, to see why ammonia and water have angles below the tetrahedral value, or to confirm that a molecule with identical substituents and no lone pairs is nonpolar. Use the formal charge mode to pick the best of several resonance structures, to see which atom in an ion carries the charge, or to catch a Lewis structure with an unreasonable charge distribution.
FAQ
- How is the steric number calculated?
- The steric number is the number of electron domains around the central atom: the count of bonded atoms plus the count of lone pairs. Triple bonds still count as one domain. A steric number of 4 with no lone pairs gives tetrahedral geometry; with one lone pair it becomes trigonal pyramidal, and with two it becomes bent.
- Why do lone pairs change the bond angle?
- A lone pair is held closer to the central atom than a bonding pair, so it repels the bonding pairs more strongly. That is why tetrahedral 109.5° opens nothing but closes to about 107° in ammonia, with one lone pair, and about 104.5° in water, with two. The tool reports these typical values so you can see the trend rather than a single ideal angle.
- How is formal charge calculated?
- Formal charge = valence electrons of the free atom − nonbonding electrons − bonds, where each bond counts once regardless of bond order. A result of zero is the most stable arrangement for that atom; positive means the atom lost electron density in the Lewis structure and negative means it gained some.
- How does the tool decide whether a molecule is polar?
- A molecule with one or more lone pairs on the central atom is reported as polar, because the lone-pair direction breaks the symmetry of the bond dipoles. Without lone pairs, identical bonded atoms cancel and the molecule is nonpolar, while different bonded atoms leave a net dipole and the molecule is polar. This is a quick guide, not a full vector sum of the bond dipoles.