Question

whats the formula for magnesium chloride with the valences balanced?
answer options:
select one of four
mgcl
mg⁺²cl
mg⁺²cl⁻¹₂
mgcl₂ (with an x mark on the mgcl₂ option)
feedback:
incorrect. this formula for magnesium chloride shows the valences balanced. try again.

Explanation:

Step1: Determine ion charges

Magnesium (\(Mg\)) has a charge of \(+2\) (valence \(+2\)), chloride ion (\(Cl^-\)) has a charge of \(-1\) (valence \(-1\)).

Step2: Balance charges

To balance the positive and negative charges, the number of \(Cl^-\) ions needed is \(2\) (since \(+2 + 2\times(-1)=0\)). So the formula is \(MgCl_2\). Wait, but the feedback says the selected \(MgCl_2\) was incorrect? Wait, no, maybe a typo in feedback. Wait, let's recheck. Magnesium is \(Mg^{2+}\), chloride is \(Cl^-\). So criss-cross method: \(Mg\) charge \(2\), \(Cl\) charge \(1\), so formula is \(MgCl_2\) (since \(2\) from \(Mg\) goes to \(Cl\) subscript, \(1\) from \(Cl\) goes to \(Mg\) subscript, but subscript \(1\) is omitted). Wait, the options: let's check each. \(MgCl\): charge would be \(+2 + (-1)=+1\), unbalanced. \(Mg^{+2}Cl\): same as \(MgCl\), charge unbalanced. \(Mg^{+2}Cl^{-1}_2\): this shows the charges and subscript, but the formula with balanced valences (and correct formula) is \(MgCl_2\) (or showing charges as \(Mg^{2+}Cl^{-}_2\)). Wait, maybe the feedback was wrong, or maybe I misread. Wait, the question is to find the formula with valences balanced. Let's do criss-cross: \(Mg^{2+}\) and \(Cl^-\), so formula is \(MgCl_2\) (because \(2\) chlorides balance \(1\) magnesium ion). So the correct formula is \(MgCl_2\) (or the option \(Mg^{+2}Cl^{-1}_2\) which shows the charges and subscript, but \(MgCl_2\) is the chemical formula with balanced valences). Wait, maybe the feedback had a typo, but based on ion charges, \(MgCl_2\) is correct. Wait, the options: the last option is \(MgCl_2\), but it was marked incorrect? Maybe the intended correct option is \(Mg^{+2}Cl^{-1}_2\) which shows the valences (charges) and subscript. Let's check: \(Mg^{+2}\) has charge \(+2\), \(2\) \(Cl^{-1}\) has total charge \(2\times(-1)=-2\), so total charge \(0\), balanced. So the correct option should be \(Mg^{+2}Cl^{-1}_2\) (or \(MgCl_2\) is the formula, but showing valences as charges, the \(Mg^{+2}Cl^{-1}_2\) shows the valences and subscript to balance).

Answer:

\(Mg^{+2}Cl^{-1}_2\) (or if considering the formula without showing charges but balanced, \(MgCl_2\); but based on showing valences (charges) and subscript, \(Mg^{+2}Cl^{-1}_2\) is the one that shows valences balanced with subscript)