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Mendeleev · Chemistry pathway · level 2

Molecular polarity

A molecule can contain polar bonds yet be nonpolar overall. Bond dipoles must be combined while considering geometry.

The essential idea

A molecule can contain polar bonds yet be nonpolar overall. Bond dipoles must be combined while considering geometry.

Example

In linear CO₂, the two C=O dipoles cancel. In bent H₂O they do not cancel, so the molecule is polar.

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Mini problem

Does a polar bond always imply a polar molecule?

Show the solution

No. Molecular symmetry can make bond dipoles cancel.

Common mistake

Do not replace reasoning with a memorized rule. Always check geometry, units, coefficients or model assumptions.

Guided exercise

Compare CO₂ and NH₃: which molecule is polar overall?

Show the detailed solution

CO₂ is linear and its bond dipoles cancel. NH₃ is trigonal pyramidal, so the dipoles do not cancel and the molecule is polar.

Avoid this

A list of polar bonds is not enough: always return to three-dimensional geometry.

Go further

Molecular polarityVSEPR
Bond vs molecule

Can polar bonds cancel?

Yes. Linear CO₂ cancels its two C=O dipoles; bent H₂O does not.

Key idea

Molecular polarity

Key idea

Molecular polarity

CO₂ is linear and its bond dipoles cancel. NH₃ is trigonal pyramidal, so the dipoles do not cancel and the molecule is polar.

Guided example

Molecular polarity

CO₂ is linear and its bond dipoles cancel. NH₃ is trigonal pyramidal, so the dipoles do not cancel and the molecule is polar.

Put it into practice

Molecular polarity

Choose a concrete case linked to Molecular polarity. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.

Check your answer

A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.

Periodic table