What type of bond is the C-Br bond in the nonpolar molecule carbon tetrabromide (CBr4)? A. polar covalent B. polar ionic C. ionic D. nonpolar covalent E. H-bond
The Correct Answer and Explanation is:
The C-Br bond in carbon tetrabromide (CBr₄) is a polar covalent bond.
Explanation:
A covalent bond occurs when two atoms share electrons. However, the type of covalent bond—whether it is polar or nonpolar—depends on the difference in electronegativity between the two atoms involved.
- Electronegativity Difference: Electronegativity is a measure of an atom’s ability to attract electrons. Carbon (C) has an electronegativity of about 2.55, while bromine (Br) has an electronegativity of about 2.96. The difference in electronegativity between carbon and bromine is about 0.41, which is not large enough to create an ionic bond but is sufficient to make the C-Br bond polar. In a polar covalent bond, the more electronegative atom (in this case, bromine) pulls the shared electrons more strongly, creating a partial negative charge (δ-) on the bromine atom and a partial positive charge (δ+) on the carbon atom.
- Polar vs. Nonpolar Covalent Bonds: In nonpolar covalent bonds, the electrons are shared equally between the atoms. This usually occurs when the two atoms have very similar electronegativities. Since carbon and bromine have a small electronegativity difference, the C-Br bond is classified as polar covalent, but the molecule as a whole can be considered nonpolar because of its symmetrical tetrahedral shape. The individual C-Br dipoles cancel each other out.
- Why Not Ionic or Other Bonds?: An ionic bond would occur if the electronegativity difference were much larger, typically greater than 1.7, leading to one atom fully transferring electrons to another. This is not the case here. An H-bond is a special type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like fluorine, oxygen, or nitrogen, which does not apply to this molecule. Therefore, the correct answer is A. polar covalent.
In conclusion, the C-Br bond is polar covalent due to the slight difference in electronegativity between carbon and bromine.
