Count the electron pairs and name the shape

You will write a small program that finds the lone pairs, the steric number and the shape of an interhalogen or xenon compound.

The idea. The central atom has some outer electrons. Each bonded atom uses one of them. The rest make lone pairs. The steric number and the number of lone pairs give the shape.

Your tasks.

1. Complete lone_pairs(outer, bonded) so that it returns the number of lone pairs on the central atom.
2. Complete steric_number(outer, bonded) so that it returns the bonded atoms plus the lone pairs.
3. Complete shape(outer, bonded) so that it looks up the pair (steric number, lone pairs) in the table SHAPES.