PHS 100 - Self Assessment

Competency #7

Answer and Explanation

What ions does the compound CaCl₂ contain?

Answer: Ca ²⁺ and Cl ^1- (twice as many chlorine ion are formed as Ca ions)

Ca is in column II of the periodic table. Neutral Ca has 2 electrons in its outer shell and by giving these electrons away, forms an Ca²⁺ ion. Cl is in column VIIA of the periodic table. Neutral Cl has 7 electrons in its outer shell and by gaining 1 electron, it forms a Cl^1- ion.

What ions does the compound MgCl₂ contain?

Answer: Mg²⁺ and Cl^1- (twice as many chlorine ion are formed as Mg ions)

Mg is in column II of the periodic table. Neutral Mg has 2 electrons in its outer shell and by giving these electrons away, forms an Mg²⁺ ion. Cl is in column VIIA of the periodic table. Neutral Cl has 7 electrons in its outer shell and by gaining 1 electron, it forms a Cl^1- ion.

What ions are likely to be formed when Cl₂ (g) reacts?

Answer: Cl^1-

Cl is in column VIIA of the periodic table. Neutral Cl has 7 electrons in its outer shell and by gaining 1 electron, it forms a Cl^1- ion.

Note that Cl always forms a Cl^1- ion. While the transition metals are unpredictable in the ions they form, elements in columns IA, IIA, IIIA, VA, VIA, and VIIA will form ions in such a way that their outer electron shells are filled.