What is the formula for magnesium phosphide?
MgP
$Mg _3 P _2$
$Mg _3\left( PO _4\right)_2$
$Mg _3\left( PO _3\right)_2$
Answer (1)
Magnesium forms M g 2 + ions.
Phosphorus forms P 3 − ions in phosphides.
Balance the charges: 3 × ( + 2 ) + 2 × ( − 3 ) = 0 .
The formula for magnesium phosphide is M g 3 P 2 .
Explanation
Problem Analysis We are asked to identify the chemical formula for magnesium phosphide from the given options.
Ions and Charges Magnesium (Mg) belongs to Group 2 of the periodic table, so it forms ions with a +2 charge ( M g 2 + ). Phosphorus (P) belongs to Group 15, and it tends to form ions with a -3 charge ( P 3 − ) when forming phosphides. To form a neutral compound, the total positive charge must equal the total negative charge.
Balancing Charges and Determining the Formula To balance the charges, we need three magnesium ions ( 3 × + 2 = + 6 ) and two phosphide ions ( 2 × − 3 = − 6 ). Therefore, the chemical formula for magnesium phosphide is M g 3 P 2 .
Final Answer The correct formula for magnesium phosphide is M g 3 P 2 .
Examples
Magnesium phosphide ( M g 3 P 2 ) is used as a rodenticide. When it reacts with moisture in the rodent's stomach, it produces phosphine gas ( P H 3 ), which is toxic and kills the rodent. This application demonstrates how understanding chemical formulas is crucial in practical applications like pest control. The balanced chemical equation for the reaction of magnesium phosphide with water is: M g 3 P 2 + 6 H 2 O → 3 M g ( O H ) 2 + 2 P H 3
