* Blue color in solution: Copper(II) ions typically form blue solutions.

* Green flame test: Copper compounds produce a characteristic green flame when heated.

* Precipitate with sodium hydroxide: Copper(II) ions react with sodium hydroxide (NaOH) to form a blue precipitate of copper(II) hydroxide (Cu(OH)₂).

Chemical Reaction:

Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂(s)

Important Note: While the combination of these characteristics strongly suggests copper(II) ions, other metals might also exhibit similar behavior. To confirm the identity, further tests like adding ammonia (forming a deep blue solution) would be necessary.