To determine which of the following can easily form an ionic bond with a cation, we need to consider the nature of each species given:
1. Sr (Strontium): Strontium is an alkaline earth metal and typically forms a cation (Sr²⁺) itself. Since it forms a cation, it will not easily form an ionic bond with another cation.
2. Ne (Neon): Neon is a noble gas, which means it is chemically inert and does not readily form ions or bonds. Therefore, it is unlikely to form an ionic bond with a cation.
3. NH₄⁺ (Ammonium ion): Ammonium ion is a cation, denoted by the positive charge. Since it is already a cation, it will not form an ionic bond with another cation.
4. PO₄³⁻ (Phosphate ion): Phosphate ion has a negative charge, indicating it is an anion. Anions are negatively charged ions that readily form ionic bonds with cations.
Since an ionic bond typically forms between a positively charged ion (cation) and a negatively charged ion (anion), the species that can easily form an ionic bond with a cation is the one that is an anion.
Hence, the phosphate ion (PO₄³⁻) can easily form an ionic bond with a cation due to its negative charge.
The answer is:
[tex]\[ PO₄^{3-} \][/tex]
