To determine which of the given ions is NOT a multivalent ion, let's investigate the common oxidation states for each:
- Ag⁺ (Silver):
- Silver typically exists in the +1 oxidation state and is not known to commonly exist in other oxidation states.
- Therefore, it is not multivalent.
- Cr³⁺ (Chromium):
- Chromium can exist in several oxidation states, including +2, +3, and +6.
- Thus, Chromium is multivalent.
- Sb⁵⁺ (Antimony):
- Antimony can exist in multiple oxidation states, including +3 and +5.
- Therefore, Antimony is multivalent.
- Cu⁺ (Copper):
- Copper typically exists in +1 and +2 oxidation states.
- This makes Copper a multivalent ion.
Given this, the ion that is NOT multivalent among the provided options is:
[tex]\[ \boxed{Ag^+} \][/tex]
Hence, the correct answer is:
[tex]\[ Ag^+ \][/tex]
