Subject: HOW IS THE STRUCTURE OF Cu-Cl DRAWN UP?

WE WERE SHOWN A DIAGRAM OF Cu-Cl--IN THE FORM OF A CUBE--AND WERE BEING 
TAUGHT ABOUT ITS STRUCTURE. MANY COMPOUNDS ARE UNIFORM AND EASY TO 
UNDERSTAND WHEN YOU LOOK AT THEM, HOWEVER, THE PROFESSOR WAS UNSURE WHY 
THIS PARTICULAR STRUCTURE DIDN'T HAVE COPPER ATOMS--I HOPE I'M EXPLAINING 
THIS CLEARLY--IN "EACH" OF THE NINE SUB-DIVIDED CUBES.  THERE WERE 
ONE-EIGHTH CHLORINE ATOMS ON EACH OF THE CORNERS, AND ONE-HALF CHLORINE 
ATOMS ON THE FACES OF THE CUBE--WHICH SEEMED NORMAL.  BUT, ENTIRE COPPER 
ATOMS SORT OF ALTERNATED THROUGHOUT THE CUBE.  ADDING UP THE CHARGES OF THE 
ATOMS, I FOUND THAT IT WAS SEEMED LIKE A VALID DIAGRAM WHEN BALANCING THE 
CHARGES AND RATIOS--STILL, WHY IS IT THAT THE COPPER IONS WERE PLACED THAT 
WAY?
PROFESSOR AND ALL, WE'RE ALL STUMPED.  THINK YOU CAN HELP ME?  

Re: HOW IS THE STRUCTURE OF Cu-Cl DRAWN UP?