Question

If you have a atom which has oxygen in it and you split it in half would it still have oxygen?

I think it will but not sure!

Answer 1

There's a very clear difference between atoms and molecules.
Atom: An atom is the smallest unit of a chemical element. For example: Oxygen Atom or Hydrogen Atom.
Molecule: A molecule is a group of two or more atoms that are held together. For example: Water Molecule (= two hydrogen and one oxygen atom that are held together)

>>> An atom CANNOT have another atom in it. So the question is wrong.
The correct question can be: "If you split an Oxygen atom to two halves, would it still be Oxygen?"
The answer is No.
If one splits oxygen atom this will happen: Some energy will be released and two smaller DIFFERENT atoms will be created. Maybe two Beryllium (Be) or Lithium (Li) atoms will be created.

You should know that splitting a small atom like Oxygen needs VERY HUGE AMOUNT OF ENERGY.