The primary difference between angular (or bent) and linear molecules lies in their shape and the arrangement of atoms around the central atom, which affects their overall molecular dipole moment.
Here's a breakdown:
-
Linear Molecules:
- Shape: Atoms are arranged in a straight line (180° bond angle).
- Central Atom: The central atom typically has two bonding pairs of electrons and no lone pairs.
- Dipole Moment: If the bonds are identical, the bond dipoles cancel out, resulting in a nonpolar molecule (zero dipole moment). If the bonds are different, the molecule can be polar, but the dipoles are oriented along the same axis.
- Example: Carbon dioxide (CO₂) - the two oxygen atoms are bonded to the central carbon atom in a straight line. The bond dipoles cancel each other out, making CO₂ a nonpolar linear molecule. Another example is Beryllium Chloride (BeCl₂).
-
Angular (Bent) Molecules:
- Shape: The molecule is bent or V-shaped (bond angle is less than 180°).
- Central Atom: The central atom has two bonding pairs of electrons and one or two lone pairs of electrons. The lone pairs repel the bonding pairs, pushing them closer together and creating the bent shape.
- Dipole Moment: The bond dipoles do not cancel out, resulting in a net dipole moment. Thus, angular molecules are typically polar.
- Example: Water (H₂O) - the two hydrogen atoms are bonded to the central oxygen atom. The two lone pairs on the oxygen atom cause the molecule to bend, and the resulting dipole moment makes water a polar molecule. Another example is Sulfur Dioxide (SO₂).
| Feature | Linear Molecule | Angular (Bent) Molecule |
|---|---|---|
| Shape | Straight Line | Bent or V-Shaped |
| Bond Angle | 180° | Less than 180° |
| Lone Pairs on Central Atom | Typically 0 | Typically 1 or 2 |
| Dipole Moment | Can be zero (nonpolar) or non-zero (polar), depending on bond polarity | Non-zero (polar) |
| Example | CO₂, BeCl₂ | H₂O, SO₂ |
In summary, a linear molecule has atoms arranged in a straight line, whereas an angular molecule is bent due to the presence of lone pairs on the central atom repelling the bonding pairs. This difference in shape significantly affects the molecule's polarity.
