Bond Polarity In a covalent bond between two atoms, the more electronegative atom will attract more electron density toward itself, causing a polar bond. The more electronegative element is the negative pole, whereas the less electronegative element is the positive pole. The direction of the dipole is always toward the more electronegative element. This is often indicated by an arrow, as shown in the figure. (Figure 1) The magnitude of the bond polarity is the difference in electronegativity values of the atoms. For example, in the molecule Cl2, the Cl Cl bond is nonpolar because there is no difference in electronegativity between two atoms of the same element. In the ClBr molecule, however, the Cl-Br bond is polar because Cl and Br have different electronegativity values. A Cl-I bond would be more polar than a Cl-Br bond because there is a greater electronegativity difference between Cl and I than between Cl and Br Figure 1 of 1 Part A In the molecule BrI, which atom is the negative pole? O Br Sutbma Request Answer Part B Of the molecules SiCly and Sil4, which has bonds that are more polar? ? SiCl4 Sil Submit Request Answer
The Correct Answer and Explanation is:
Correct Answers:
Part A:
The Br atom is the negative pole in the Br–I molecule.
Part B:
SiCl₄ has bonds that are more polar than those in SiI₄.
Detailed Explanation (300+ words):
Bond polarity refers to the unequal sharing of electrons between two atoms in a covalent bond due to a difference in electronegativity—the tendency of an atom to attract electrons toward itself. The atom with the higher electronegativity attracts the shared electrons more strongly and becomes the negative pole (δ⁻), while the atom with lower electronegativity becomes the positive pole (δ⁺).
Part A: Br–I molecule
In the diatomic molecule BrI, the bond is between bromine (Br) and iodine (I).
The electronegativity values on the Pauling scale are approximately:
- Br (bromine): 2.96
- I (iodine): 2.66
Since Br has a higher electronegativity than I, it pulls the shared electron pair closer to itself. As a result, Br becomes the negative pole (δ⁻), and I becomes the positive pole (δ⁺). Therefore, the direction of the dipole points toward Br.
Part B: Comparing SiCl₄ and SiI₄
Both SiCl₄ (silicon tetrachloride) and SiI₄ (silicon tetraiodide) are tetrahedral molecules composed of silicon covalently bonded to four halogen atoms.
Let’s compare the electronegativity differences between silicon (Si) and the halogen atoms:
- Si (silicon): 1.90
- Cl (chlorine): 3.16
- I (iodine): 2.66
Electronegativity difference:
- Si–Cl: 3.16 − 1.90 = 1.26
- Si–I: 2.66 − 1.90 = 0.76
Since the Si–Cl bond has a greater electronegativity difference than the Si–I bond, the Si–Cl bond is more polar. Therefore, the molecule SiCl₄ has more polar bonds than SiI₄.
Summary:
- Br is the negative pole in BrI due to its higher electronegativity.
- SiCl₄ has more polar bonds than SiI₄ because chlorine is more electronegative than iodine, resulting in a larger electronegativity difference.