The ionic compound Pb3(PO4)2 is called:
lead (II) phosphate
Lead (II) phosphite
Lead (III) phosphate
lead (IV) phosphate
The Correct Answer and Explanation is :
The correct name for the ionic compound Pb₃(PO₄)₂ is lead (II) phosphate.
Explanation:
To understand why, let’s break down the naming of the compound:
- Pb₃(PO₄)₂ is composed of two ions:
- Lead (Pb): Lead can form multiple oxidation states, specifically +2 and +4. This means that lead can have different charges in different compounds.
- Phosphate (PO₄)²⁻: Phosphate is a polyatomic ion, and its formula is PO₄ with a charge of -3.
- Determining the oxidation state of lead:
- In Pb₃(PO₄)₂, we have three lead (Pb) atoms and two phosphate (PO₄) ions.
- The charge of one phosphate ion (PO₄) is -3. With two phosphate ions, the total charge from the phosphate ions is 2 × (-3) = -6.
- Since the compound must be neutral overall, the charges from the lead atoms must balance the -6 charge from the phosphate ions. Therefore, the total positive charge from the three lead ions must be +6.
- To achieve a +6 charge with three lead atoms, each lead must have an oxidation state of +2.
- This means lead in this compound is in the +2 oxidation state.
- Naming the compound:
- When naming ionic compounds, if the metal can have more than one oxidation state, the oxidation state is indicated in parentheses using Roman numerals.
- Since lead has a +2 oxidation state in this compound, we name the compound lead (II) phosphate.
The other options are incorrect because:
- Lead (III) phosphate would indicate that lead has a +3 oxidation state, which is not the case here.
- Lead (IV) phosphate would indicate a +4 oxidation state, which also does not apply in this compound.
- Lead (II) phosphite refers to a different anion, phosphite (PO₃³⁻), rather than phosphate (PO₄³⁻), so it is not correct for Pb₃(PO₄)₂.