I want to ask if someone is there. Can both terms be used to ask if a person is there/are you there? いますか or いるの？
I assume what you are asking is "どなたか／誰か + いますか？／いるの？" construction.
どなたか／誰か + いますか？
means you want to get the reply from someone if they are staying there.
So, if someone is replying, it might relieve you.
どなたか／誰か + いるの？
means you are wondering if someone is there since it is unlikely/no sign someone is staying there. So, if someone is replying, it might surprise you.