If you build an atom with 6 protons, 7 neutrons, and 7 electrons, what element
have you created?

First off, you cannot "build" an atom because doing so would throw the Law of Conservation of Matter out the window, and we don't want to do that.

However, I get what you're asking... 6 protons, 7 electrons and 7 neutrons would make carbon-13.

it's c (engineer's do their work with mechanical stuff not on any living being)