Final answer:
Electronegativity determines whether an atom acquires a positive or negative partial charge in polar covalent bonds, with the more electronegative atom gaining a partial negative charge.
Step-by-step explanation:
The physical property of an element that determines whether it acquires a positive or negative partial charge when participating in polar covalent bonds is called electronegativity. Electronegativity is a measure of an atom's ability to attract shared electrons in a bond. The greater the electronegativity of an atom, the more it attracts the shared electrons, resulting in that atom acquiring a partial negative charge. Conversely, the atom with lower electronegativity ends up with a partial positive charge due to the unequal electron distribution.