electronic configuration - In which cases does the 3d subshell take precedence over the 4s subshell?

I've learnt in Chemistry that for example in Chromium, the 4s subshell only has one electron in favor of making the 3d subshell half-full. Also, for Copper the same happens.

What other circumstances does this happen under? Do ions obey the same pattern, e.g. Mn+?