Fill in the name and empirical formula of each ionic compound that could be formed from the ions in this table:
| cation | anion | empirical formula | name of compound |
|---|---|---|---|
| [tex]$Mg^{2+}$[/tex] | [tex]$MnO_4^-$[/tex] | | |
| [tex]$Cr^{3+}$[/tex] | [tex]$OH^-$[/tex] | | |
| [tex]$Ca^{2+}$[/tex] | [tex]$NO_3^-$[/tex] | | |
Answer (1)
Balance the charges between the cation and anion to determine the correct ratio of ions.
Write the empirical formula with the cation first, followed by the anion, using subscripts to indicate the number of each ion.
Name the compound by stating the cation name (with Roman numerals for transition metals) followed by the anion name.
The empirical formulas and names are: M g ( M n O 4 ) 2 (Magnesium permanganate), C r ( O H ) 3 (Chromium(III) hydroxide), and C a ( N O 3 ) 2 (Calcium nitrate).
M g ( M n O 4 ) 2 , Magnesium permanganate ; C r ( O H ) 3 , Chromium(III) hydroxide ; C a ( N O 3 ) 2 , Calcium nitrate
Explanation
Understanding the Problem We are given a table with cations and anions. Our task is to determine the empirical formula and the name of the ionic compound formed by each cation-anion pair.
Objective and Strategy For each cation-anion pair, we need to balance the charges to form a neutral compound. The empirical formula represents the simplest whole-number ratio of ions in the compound. The name of the compound follows standard nomenclature rules for ionic compounds.
Magnesium Permanganate
M g 2 + and M n O 4 − : Magnesium has a +2 charge, and permanganate has a -1 charge. To balance the charges, we need two permanganate ions for each magnesium ion. The empirical formula is M g ( M n O 4 ) 2 . The name of the compound is Magnesium permanganate.
Chromium(III) Hydroxide
C r 3 + and O H − : Chromium(III) has a +3 charge, and hydroxide has a -1 charge. To balance the charges, we need three hydroxide ions for each chromium(III) ion. The empirical formula is C r ( O H ) 3 . The name of the compound is Chromium(III) hydroxide.
Calcium Nitrate
C a 2 + and N O 3 − : Calcium has a +2 charge, and nitrate has a -1 charge. To balance the charges, we need two nitrate ions for each calcium ion. The empirical formula is C a ( N O 3 ) 2 . The name of the compound is Calcium nitrate.
Final Answer The completed table is:
cation
anion
empirical formula
name of compound
M g 2 +
M n O 4 −
M g ( M n O 4 ) 2
Magnesium permanganate
C r 3 +
O H −
C r ( O H ) 3
Chromium(III) hydroxide
C a 2 +
N O 3 −
C a ( N O 3 ) 2
Calcium nitrate
Examples
Ionic compounds are everywhere! For example, table salt (sodium chloride, NaCl) is an ionic compound we use daily. Understanding how these compounds form helps us predict the properties of materials, design new medicines, and even understand geological processes. For instance, the formation of stalactites and stalagmites in caves involves the precipitation of calcium carbonate ( C a C O 3 ), another ionic compound, from water. The ability to predict the formulas and names of ionic compounds is fundamental to chemistry and material science.
