The formation of a bond between hydrogen and a highly electronegative atom results in a. polarity b. dipole c. metallic bond d. electrovalent bond.

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28. The formation of a bond between hydrogen and a highly electronegative atom results in a. polarity b. dipole c. metallic bond d. electrovalent bond.

• Explanation: When hydrogen bonds with a highly electronegative atom (like oxygen, nitrogen, or fluorine), the electron pair in the covalent bond is pulled more towards the electronegative atom. This creates an uneven distribution of charge, with the electronegative atom gaining a partial negative charge ($\delta^-$) and the hydrogen atom gaining a partial positive charge ($\delta^+$). This characteristic of having separated partial charges within the bond is called polarity. A dipole is the physical representation of this charge separation.
• Answer: $\boxed{\text{a. polarity}}$

29. The molecule that has a non-polar covalent bond is a. H₂O b. HCl c. NH₃ d. Cl₂

• Explanation: A non-polar covalent bond forms between two atoms that have identical or very similar electronegativity, leading to an equal sharing of electrons.
  • a. H₂O (Water): The O-H bonds are polar because oxygen is significantly more electronegative than hydrogen.
  • b. HCl (Hydrogen chloride): The H-Cl bond is polar because chlorine is more electronegative than hydrogen.
  • c. NH₃ (Ammonia): The N-H bonds are polar because nitrogen is more electronegative than hydrogen.
  • d. Cl₂ (Chlorine gas): This molecule consists of two identical chlorine atoms. Since both atoms have the same electronegativity, the electron pair is shared equally, resulting in a non-polar covalent bond.
• Answer: $\boxed{\text{d. Cl₂}}$