Molecular shape
Molecular shape depends on how electron domains are arranged around atoms. Bonding and lone pairs influence angles and therefore the observed geometry.
The essential idea
Molecular shape depends on how electron domains are arranged around atoms. Bonding and lone pairs influence angles and therefore the observed geometry.
Example
CH₄ is tetrahedral around carbon, whereas H₂O is bent because oxygen's lone pairs alter the shape.
Mini problem
Why do CO₂ and H₂O have different shapes?
Show the solution
CO₂ has two main bonding domains around carbon with no central lone pair; H₂O has two bonds and two lone pairs around oxygen.
Common mistake
Do not replace reasoning with a memorized rule. Always check geometry, units, coefficients or model assumptions.
Guided exercise
Predict the shape of NH₃ around nitrogen using VSEPR.
Show the detailed solution
Nitrogen has three N–H bonds and one lone pair: four electron domains in total. Electron geometry is tetrahedral, while molecular shape is trigonal pyramidal.
Avoid this
Do not confuse electron geometry with molecular shape: lone pairs count in the first but are not atoms in the second.