Final answer:
The substance with a nonpolar covalent bond among the options provided is d. H2, where both hydrogen atoms have the same electronegativity, thereby sharing electrons equally.
Step-by-step explanation:
Understanding Covalent Bonds
To determine which of the listed substances contains a nonpolar covalent bond, we must first understand the difference between nonpolar covalent bonds, polar covalent bonds, and ionic bonds. A nonpolar covalent bond is a type of chemical bond where two atoms share a pair of electrons with each other equally because they have similar electronegativities. On the other hand, a polar covalent bond occurs between two atoms of differing electronegativities, which causes an uneven distribution of electron density. An ionic bond typically forms when the difference in electronegativity between the two atoms is significantly large, often greater than 1.7, leading to the complete transfer of electrons from one atom to another, resulting in oppositely charged ions.
Identifying the Nonpolar Covalent Bond
Considering the substances given (a. PH₃, b. KCl, c. IBr, d. H2, e. CaF₂), the one with a nonpolar covalent bond is most likely d. H2, as both hydrogen atoms have the same electronegativity. In contrast, substances like KCl and CaF₂ are likely to form ionic bonds due to the significant difference in electronegativity between the metal and non-metal involved. Substances like PH₃ and IBr may have polar covalent bonds due to a difference in electronegativity between the constituent atoms, though in the case of IBr, the difference is quite small and could be considered a slightly polar covalent bond.