How do I decide whether something is polar or not?
Polar occurs whenever we have opposit charged ions. such HF, H being positively charged ion and F being negatively charged ion.
Non Polar occurs whenever the two ions are identical. such as Hydrogen ion mixing with another Hydrogen ion to form hydrogen molecules because the ywo hydrogen are positively charged ions.
For binary compounds, a difference in electronegativity leads to a polar compound. For example, CsF. Cs as EN of about 0.8 or so and F has EN of about 4.0. The difference is >3.0 and this is an ionic (polar) compound.
For molecules, two criteria must be satisfied.
a. There must be an EN difference between the central atom and at least one of the other atoms AND (not or)
b. The compound must NOT be symmetrical in three dimensions. An example is CH4 (EN difference between C and H) BUT the molecule is symmetrical. NH3, EN difference AND it is not symmetrical (NH4^+ is symmetrical but not NH3).
To determine whether a molecule is polar or nonpolar, you need to consider its molecular geometry and the polarity of its individual bonds. Here's a step-by-step approach to help you decide:
1. Determine the molecular geometry: Use the Lewis structure or the VSEPR (Valence Shell Electron Pair Repulsion) theory to determine the molecular shape. This will depend on the number of valence electrons and the number of bonded and lone pairs of electrons around the central atom.
2. Identify the individual bond polarities: Determine the electronegativity difference between the atoms involved in each bond. Electronegativity is the ability of an atom to attract electrons towards itself. You can check a table of electronegativity values to compare them.
3. Consider the symmetry of the molecule: If the molecule has symmetry such that the polar bonds are arranged symmetrically around the central atom, the bond polarities may cancel each other out, resulting in a nonpolar molecule.
4. Determine the molecular polarity: If the molecule has an uneven distribution of charge due to the presence of polar bonds that do not cancel out, it will be a polar molecule. If the bond polarities cancel each other out, the molecule will be nonpolar.
Remember that polar molecules have a positive and negative end due to an uneven distribution of charge, with the negative end being attracted to the positive end of other polar molecules. Nonpolar molecules have an even distribution of charge and do not have distinct positive and negative ends.
It's essential to practice and familiarize yourself with the concepts of molecular geometry, electronegativity, and symmetry to become proficient at determining the polarity of molecules.