In a face centered cubic structure, every atom has 12 neighbors. Which arrangement of balls serves as the best model for this structure?
a) 8 balls at the corners of a cube, 6 balls in the centers of the cubes faces.
b) 8 balls at the corners of a cube.
c) 8 balls at the corners of a cube, and one ball in the center of the cube.
d) 12 balls arranged equally apart from eachother around a circle.