What is the full ground state electron configuration of ##O^+##?

##O^+=1s^(2)2s^(2)2p^3##

Typically, an atom of ##O## has 8 electrons, so based on the system that would be ##1s^(2)2s^(2)2p^(4)##, or ##2+2+4=8e^-##.

However, ##O^+## means you've lost an electron, hence the positive charge. Thus, you subtract an electron: ##8\color(teal)(-1)=\color(red)(7)e^-## ##1s^(2)2s^(2)2p^(4\color(teal)(-1))\rArr1s^(2)2s^(2)2p^(\color(red)(3))##

Electron configuration rule: