Final answer:
A polar molecule has an asymmetric distribution of electrons that leads to one end being slightly negative and the other slightly positive. Examples include water and hydrogen fluoride (HF), which display this polarity due to differences in electronegativity between their constituent atoms.
Step-by-step explanation:
A polar molecule is characterized by an unequal distribution of electrons between the atoms which leads to one end of the molecule having a slight negative charge and the opposite end having a slight positive charge. This distribution occurs because atoms have different electronegativities, causing the electrons to be more attracted to one nucleus over another.
For example, water (H2O) is a polar molecule. The oxygen atom has a higher electronegativity compared to the hydrogen atoms; thus, the electrons are more strongly attracted towards the oxygen atom. As a result, the oxygen end is slightly negative, while the hydrogen end is slightly positive, making water a dipole. Another common example of a polar molecule is hydrogen fluoride (HF), where the fluorine atom's higher electronegativity compared to hydrogen leads to a pronounced dipole moment.
The term polarization refers to the slight shift of positive and negative charges to opposite ends of an atom or molecule. The asymmetric charge distribution of a polar molecule can have a significant impact on the physical properties of the substance, such as solubility and boiling point, and plays a critical role in chemical reactivity and biological interactions.