Cu2+?

Right, Cu2+ is the well-known and watery solution blue copper ion, more precisely the copper(II)ion.

You can’t simply create this by dissolving copper in acids, such as zinc, for example, because copper is too noble. One possibility is dissolution in concentrated sulfuric acid because it also acts oxidizing and is thereby reduced to sulfur dioxide.

A simple solution (double sense of word) would be to make the plush of copper, then it dissolves to the extent that copper is separated from the minus pole. Thus, copper is also electrolytically purified, “refined”.

To ask why copper is predominantly bivalent, although it is in the 1st subgroup:
Transition metals generally occur in exposed oxidation stages, which can also be difficult to predict as a skilled person. Generally, +2 and +3 are fairly spread because this is simply a good compromise between energy expenditure and energy gain.
But why of the 3 elements of the group, copper, silver and gold, copper is predominantly bivalent, silver is almost only monovalent and gold is most preferred trivalent, that has not yet been able to explain here, and there are people with much more understanding.

And, of course, the electrons go to the connecting partner. There are always anions to the cations. You therefore have copper(II) chloride or copper(II) sulfate, with chloride or sulfate anions as compensation.