Competency #6

Answer and Explanation

The correct answer is B.

Which of the following statements best describes ionic bonding between magnesium and chlorine?

Since this question involves ionic bonding, lets first look at what ions magnesium and chlorine form. Looking at the Bohr model for magnesium, we see that it can lose 2 electrons and form a Mg2+ ion (12 protons minus 10 electrons = +2 charge). Chlorine, on the other hand, will gain 1 electron to fill its outer shell and form a Cl 1- ion (17 protons – 18 electrons = -1 charge).

  1. One magnesium ion will form an ionic bond with one chlorine ion. An ionic compound must have a neutral charge. Let's look at what the charge would be for MgCl.

    Charge = Charge of Mg ion + Charge of Cl ion Charge = +2 + -1 Charge = +1

    We see that MgCl is not neutral and thus magnesium and chlorine do not combine in this ratio.

  2. One magnesium ion will form an ionic bond with two chlorine ions. This is the correct answer. An ionic compound must have a neutral charge. Let's look at what the charge would be for MgCl 2.

    Charge = Charge of Mg ion + Charge of Cl ion + Charge of Cl ion Charge = +2 + -1 + -1 Charge = 0

    We see that MgCl 2 is neutral and thus magnesium and chlorine do combine in this ratio.

  3. Two magnesium ions will form ionic bonds with one chlorine ion.

    An ionic compound must have a neutral charge. Let's look at what the charge would be for Mg 2Cl.

    Charge = Charge of Mg ion + Charge of Mg ion + Charge of Cl ion Charge = +2 + +2 + -1 Charge = +3

    We see that Mg2Cl is not neutral and thus magnesium and chlorine do not combine in this ratio.

  4. The outer electron shells of magnesium and chlorine will overlap. The overlap of outer electron shells is a characteristic of covalent bonding.
  5. No ionic bonds can form between magnesium and chlorine. As seen in choice B, this is not correct.
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