Question

when naming the compound ba₃(po₄)₂
it is called barium phosphate because ba is a b-metal
it is called tribarium diphosphate because ba is an a-metal
it is called barium phosphate because ba is an a-metal
it is called barium diphosphate because po₄⁻³ is a polyatomic ion

Explanation:

To name \( \text{Ba}_3(\text{PO}_4)_2 \), we analyze the ions. Barium (\( \text{Ba} \)) is an A - metal (alkaline earth metal, group 2), so it forms a \( + 2 \) ion (\( \text{Ba}^{2+} \)). The polyatomic ion is phosphate (\( \text{PO}_4^{3 - } \)). For ionic compounds with A - metals (which have a fixed charge), we use the name of the metal followed by the name of the polyatomic ion.

• Option 1: Saying Ba is a B - metal is wrong (B - metals have variable charges, Ba has a fixed \( + 2 \) charge).
• Option 2: The formula does not have \( \text{P}_2\text{O}_7^{4 - } \) (diphosphate) ion, so "Tribarium Diphosphate" is incorrect.
• Option 4: The ion here is phosphate (\( \text{PO}_4^{3 - } \)), not diphosphate, so this is wrong.
• Option 3: Ba is an A - metal (fixed charge \( + 2 \)), and the compound is named Barium Phosphate as we use the metal name and the polyatomic ion (phosphate) name.

Answer:

C. it is called Barium Phosphate because Ba is an A - Metal (assuming the third option is labeled C; if the original options had labels like A, B, C, D with the third being C, then the answer is C. it is called Barium Phosphate because Ba is an A - Metal)