What arrangement of electrons would result in a non polar molecule?
The Correct Answer and Explanation is:
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Correct answer:
A nonpolar molecule results when the electrons are arranged so that the molecule has a symmetrical electron distribution and no overall dipole moment. This typically happens when the central atom has no lone pairs and is bonded to identical atoms arranged symmetrically, causing the individual bond dipoles to cancel out.
Explanation
The polarity of a molecule depends largely on the arrangement of its electrons, both bonding and nonbonding, around the central atom. Electrons in chemical bonds create dipoles due to differences in electronegativity between atoms. When these dipoles do not cancel out, the molecule is polar, meaning it has a net dipole moment. However, when the dipoles cancel, the molecule is nonpolar.
For a molecule to be nonpolar, the electrons must be arranged so the molecular geometry is symmetrical. This symmetrical distribution ensures that any bond dipoles (partial charges along bonds) are evenly distributed in such a way that their vector sum is zero.
Key factors for nonpolar molecules:
- Symmetrical Molecular Geometry:
Common shapes like linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral geometries can produce nonpolar molecules if all the surrounding atoms are identical and the molecule has no lone pairs on the central atom. For example, carbon dioxide (CO₂) is linear and symmetrical, with two polar bonds pointing in opposite directions, canceling each other out, resulting in a nonpolar molecule. - No Lone Pairs on Central Atom:
Lone pairs of electrons occupy space and create regions of negative charge that distort symmetry. For example, water (H₂O) has two lone pairs on oxygen, leading to a bent shape and a polar molecule. - Identical Surrounding Atoms:
If the atoms attached to the central atom differ in electronegativity, the bond dipoles differ and the molecule often becomes polar, even if symmetrical. - Equal Electron Distribution:
The bonding electrons are shared equally or arranged symmetrically so the molecule’s net dipole moment is zero.
Examples:
- Nonpolar: Methane (CH₄) with tetrahedral symmetry, carbon tetrachloride (CCl₄), and nitrogen gas (N₂).
- Polar: Ammonia (NH₃) due to lone pair distortion, and water (H₂O).
In summary, an arrangement of electrons that leads to a symmetrical shape and equal pull in all directions results in a nonpolar molecule. This occurs when there are no lone pairs on the central atom and the bonded atoms are identical, causing bond dipoles to cancel each other out completely.
