The correct formula for iron (II) phosphide is
a. Fe₃P₂
b. Fe₂P₃
c. FeP
d. Fe₂P
e. FeP₂
The Correct Answer and Explanation is:
The correct formula for iron (II) phosphide is a. Fe₃P₂.
Explanation:
To determine the correct formula for iron (II) phosphide, we need to consider the oxidation states of the elements involved, iron (Fe) and phosphorus (P), and use these to form a neutral compound.
- Iron (II): The Roman numeral (II) in the name “iron (II) phosphide” indicates that iron has an oxidation state of +2. This means that for each iron (Fe) atom, there is a charge of +2.
- Phosphorus: Phosphorus, as an element in group 15 of the periodic table, typically forms an anion with a charge of -3. This is because phosphorus tends to gain three electrons to achieve a stable electron configuration, resulting in the phosphate ion, ( P^{3-} ).
To form a neutral compound, the total positive charge from the iron atoms must balance out the total negative charge from the phosphorus atoms. Here’s how we determine the correct ratio:
- The charge from iron is +2 per atom, and the charge from phosphorus is -3 per atom.
- The least common multiple (LCM) of 2 (from iron) and 3 (from phosphorus) is 6. To balance the charges, we need three iron (Fe) atoms to provide a total positive charge of ( 3 \times +2 = +6 ), and two phosphorus (P) atoms to provide a total negative charge of ( 2 \times -3 = -6 ).
Thus, the correct formula is Fe₃P₂, where three iron atoms combine with two phosphorus atoms to form a neutral compound. This is the formula for iron (II) phosphide.
Other Choices:
- b. Fe₂P₃: This would imply an oxidation state of +3 for iron, but the compound is iron (II), meaning the oxidation state of iron should be +2.
- c. FeP: This formula would suggest a 1:1 ratio of Fe and P, which is incorrect based on their respective oxidation states.
- d. Fe₂P: This formula would not balance the charges correctly for iron (II) and phosphorus (P).
- e. FeP₂: This would imply two phosphorus atoms for every iron atom, which would not balance the charges of +2 for iron and -3 for phosphorus.
Thus, the correct answer is a. Fe₃P₂.