Final answer:
In a polar covalent bond, the more electronegative atom gains a partial negative charge (δ−), while the other atom has a partial positive charge (δ+), due to the unequal distribution of shared electrons.
Step-by-step explanation:
In a polar covalent bond, the electrons shared between atoms are not evenly distributed. This leads to one of the atoms having a greater electron density and attracting the bonding electrons more than the other atom. As a result, the more electronegative atom gains a partial negative charge (designated as δ−), whereas the other atom has a partial positive charge (δ+). This is due to the concept of electronegativity, which measures an atom's tendency to attract bonding electrons to itself.
For instance, the molecule of water (H2O) has a polar covalent bond where the oxygen atom is more electronegative than the hydrogen atoms. Hence, the shared electrons are more attracted towards oxygen, providing it with a δ− charge, while the hydrogen atoms have a δ+ charge.
The polarity of a molecule can affect its physical properties and reactivity, which is crucial in chemical reactions. If a molecule has multiple polar covalent bonds, the overall polarity will depend on whether these individual bond polarities cancel each other out or contribute to a net dipole moment.