Someone: used when we want to refer to a person but we don't know or don't care who:
Someone ate all the cookies!
If someone helps me, I can finish quickly.
I hope I find someone to marry.
From googling the phrase +"some one", it is most commonly used in error - the writer actually meant "someone". It might possibly come up in English but it would be very rare. If you see "some one", it is probably an error.
If you have a question about the English language and would like to ask one of our many English teachers and language experts, please click the button below to let us know: