Question

when naming binary ionic compounds with metals that typically form only one type of ion, a roman numeral is always included in the name. true false a student writes the formula for magnesium chloride as mgcl. using your understanding of the criss - cross method and the charges of magnesium (mg²⁺) and chloride (cl⁻), explain why this formula is incorrect and provide the correct formula. the formula is incorrect because the charges were not swapped correctly; the correct formula is mg₂cl. the formula is incorrect because the signs of the charges should be included in the formula; the correct formula is mg²⁺cl⁻¹. the formula is incorrect because the charges were not balanced; the correct formula is mgcl₂. the formula is incorrect because the charge of magnesium should be a subscript for chlorine, and the charge of chlorine should be a subscript for magnesium; the correct formula is mg₁cl₁.

Explanation:

1. For the first statement, when naming binary ionic compounds with metals that form only one type of ion, a Roman numeral is not included. For example, sodium chloride (NaCl), sodium always forms a +1 ion and no Roman numeral is used in its name.
2. For the magnesium - chloride formula, magnesium has a +2 charge ($Mg^{2 + }$) and chloride has a - 1 charge ($Cl^{-}$). Using the criss - cross method, the charges are used as subscripts to balance the compound. So the correct formula is $MgCl_{2}$ as the charges must be balanced.

Answer:

1. False
2. The formula is incorrect because the charges were not balanced; the correct formula is $MgCl_{2}$