The electronic configuration of copper is shown below;
[Kr]4d10 5s1
We can see that there is only one 5s1 electron. Hence Ag^+ tends to display a pseudo noble gas configuration. This pseudo noble gas configuration explains why silver is prevalent in the +1 oxidation state.
The other transition metals have many stable oxidation states found in nature. Chromium is observed both in +3 and +6 oxidation states. Iron is found in +2 and +3 oxidation states and copper is mostly stable in the +2 oxidation state since the +1 oxidation state readily disproportionate.
Hence silver tends to have only a single ionic charge for reasons aptly stated above.
As metals are giant lattice structures, the number of electrostatic forces to be broken is extremely large, and so metals have high melting and boiling points. This means that the melting point and boiling point of metals are more similar to those for ionic compounds than for covalent substances.
Explanation: In science a person has to be curious on how things work. Key word how. Why makes sense but how is the better answer. How many is a specific question. But it doesn't involve the whole spectrum of science. What also doesn't make sense.