What is the correct formula that would result from the combination of the two ionic species?
[tex]$Mg ^{2+}$[/tex] and [tex]$PO _4{ }^{3-}$[/tex]
A. [tex]$Mg _3(PO _4)_2$[/tex]
B. [tex]$Mg (PO _4)_3$[/tex]
C. [tex]$MgPO _4$[/tex]
D. [tex]$Mg _2(PO _4)_3$[/tex]
Answer (1)
Determine that the compound must be neutral.
Find the least common multiple (LCM) of the charges 2 and 3, which is 6.
Determine that 3 magnesium ions ( M g 2 + ) are needed for a +6 charge and 2 phosphate ions ( P O 4 3 − ) are needed for a -6 charge.
Combine the ions to form the neutral compound M g 3 ( P O 4 ) 2 .
M g 3 ( P O 4 ) 2
Explanation
Understanding the Problem We are asked to determine the correct chemical formula that results from the combination of magnesium ions ( M g 2 + ) and phosphate ions ( P O 4 3 − ). The key to solving this problem is to recognize that the compound formed must be electrically neutral. This means the total positive charge from the magnesium ions must equal the total negative charge from the phosphate ions.
Finding the Least Common Multiple (LCM) To find the correct ratio of magnesium to phosphate ions, we need to find the least common multiple (LCM) of the charges, which are 2+ and 3-. The LCM of 2 and 3 is 6.
Determining the Number of Ions To achieve a total positive charge of +6, we need 3 magnesium ions, since each magnesium ion has a charge of +2 ( 3 M g 2 + = + 6 ). To achieve a total negative charge of -6, we need 2 phosphate ions, since each phosphate ion has a charge of -3 ( 2 P O 4 3 − = − 6 ).
Forming the Neutral Compound Therefore, the correct formula for the ionic compound formed by magnesium and phosphate ions is M g 3 ( P O 4 ) 2 . This formula indicates that there are 3 magnesium ions for every 2 phosphate ions, resulting in a neutral compound.
Examples
Understanding how ionic compounds form is crucial in various real-world applications. For instance, in agriculture, fertilizers often contain ionic compounds like magnesium phosphate to provide essential nutrients to plants. The correct formulation ensures that plants receive the right balance of magnesium and phosphorus, promoting healthy growth. Similarly, in medicine, certain drugs are formulated as ionic compounds to enhance their absorption and effectiveness in the body. Knowing the correct chemical formula is essential for accurate dosage and therapeutic outcomes.
