This package, along with Chemistry::Atom and Chemistry::Bond, includes
basic objects and methods to describe molecules.

The core methods try not to enforce a particular convention. This means
that only a minimal set of attributes is provided by default, and some
attributes have very loosely defined meaning. This is because each program
and file type has different idea of what each concept (such as bond and
atom type) means. Bonds are defined as a list of atoms (typically two) with
an arbitrary type. Atoms are defined by a symbol and a Z, and may have 3D
and internal coordinates (2D coming soon).