Predicting a shape with VSEPR

A dictionary links each pair of numbers, electron pairs and lone pairs, to the name of a shape. You will count the pairs on the central atom of sulphur tetrafluoride, find its lone pairs, and look up its shape.

The idea. Each fluorine is singly bonded and adds one electron. Half of all the electrons gives the number of pairs.

Your tasks.

1. Set pairs to the number of electron pairs on the central atom.
2. Set lone to the number of lone pairs.
3. Set shape to the name of the shape, from the dictionary.