Why does a silver ion only have a single positive charge?

I haven't been into chemistry for a very long time, but if you have a silver ion Ag+, I would think that means that it is minus one electron and could accept one electron from a different element that has one electron to spare. A negative charge would mean an excess of electrons. A positive charge indicates a lack of electrons to balance the ion into neutral. So Ag+ would mean that it is lacking one electron (negative charge) to make it neutral, and thus would not have 1 valence electron. I hope I haven't got this all screw up! Like I said, it's been a very long time since I was into chemistry. :-)