How do you count the number of atoms in a unit cell?

Question

I have been asked to determine the number of barium and oxygen atoms in a unit cell of barium oxide.
Do i count each corner barium as an 1/8 and each side atom as a half?

Answer 1

Each side is a 1/2 because the molecule is split into two pieces. All atoms fully inside the square are counted as a whole.

There's a good website that will allow you to draw out the structure and see it visually:
http://www.chm.davidson.edu/ChemistryApplets/Crystals/UnitCells/sc.html

Answer 2

Yes.