what do we mean when we describe a molecule as being polar?
It means two things.
1. It means that the shared pair of electrons is closer to one of the atoms (the more electronegative one) than to the other and
2. It means that the atoms have a slight charge (one has a slightly + charge and the other a slightly -(negative) charge.)
Thanks!
When we describe a molecule as being polar, it means that there is an uneven distribution of electron density within the molecule, causing the molecule to have a positive and a negative end.
To understand why a molecule is polar, we need to consider its molecular geometry and the electronegativity of its atoms.
1. Check the molecular geometry: The shape of a molecule influences its polarity. A molecule can have a linear, bent, trigonal planar, tetrahedral, or any other geometry.
2. Determine the electronegativity difference: Electronegativity is a measure of an atom's ability to attract electrons towards itself. In a covalent bond, if there is a significant difference in electronegativity between the atoms involved, the more electronegative atom will attract the shared electrons more strongly, creating a polarity.
3. Look for polar bonds: If there is a difference in electronegativity between two atoms in a bond, the bond is said to be polar. The direction of the bond's polarity is from the less electronegative atom (partial positive charge) towards the more electronegative atom (partial negative charge).
4. Consider the molecular symmetry: If a molecule has polar bonds, its overall polarity depends on the symmetry of the molecule. If the polar bonds are arranged symmetrically, the polarities may cancel out, resulting in a nonpolar molecule. However, if the arrangement is asymmetrical, the molecule will be polar.
To summarize, a molecule is considered polar when it has polar bonds due to differences in electronegativity between the atoms involved, and when the molecular geometry is asymmetrical.