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MCAT Chemistry Question — Ionic Bonds

  • by John
  • Feb 28, 2017
  • MCAT Question of the Day

Which of the following pure compounds form ionic bonds?

 

  1. CaCl2
  2. HCl
  3. NaF
  4. Mg(OH)2

 

  1. I  only
  2. I and II only
  3. I, III, and IV
  4. I, II, III, and IV
Click for Explanation
An ionic bond is formed between two atoms when one atom loses one or more electrons and another atom gains one or more electrons. This results in a positively charged cation and a negatively charged anion. The electrostatic attraction between the oppositely charged ions creates the bond, which can be measured by the finding the difference in electronegativity of the two atoms.

Generally, a metal and nonmetal atom form ionic bonds. Metals prefer to give up electrons to form cations whereas nonmetals prefer their reduced anion form. In the case of CaCl2, NaF, and Mg(OH)2, each atom contains a metal that is bonded to a nonmetal. These all represent ionic bonds. While hydrochloric acid tends to dissociate in water to form H+ and Cl, a pure solution cannot. Pure HCl contains two nonmetals, which forms a polar covalent bond. Therefore, C is the correct answer.

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