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Phase 2

The customer started to indicate that there were more ways name atoms. The model seemed to be too restrictive to be able to handle these other names. The new definitions were received below.

Using inheritance to model all of these new types would have made the model much too complicated. And the types can possibly overlap with other types, so there is no clean separation using inheritance.

Additional Definitions

Alkali metals	Shining, soft, low melting metals. Group 1A
Alkaline earth metals	Less reactive than alkali. Group 2A
Halogen	(halas = salt) Colorful, non-corosive. Group 7A
Noble gas	Colorless gases. Group 8A
Lanthanides
Actinides
Inner transition metal groups	Between groups 2A and 3A
Molecule	Groups of atoms held together with covalent bonds
Chemical compound	A pure substance that can be broken down into simpler substances by chemical reactions
Mixture	Can vary in composition and properties. Can be separated without changing identities
Chemical formula	Shows using subscripts how many atoms of different elements are combined in a chemical compound

The additional definitions were used to create the following drawing. The disadvantage with this drawing is that we lost some clarity because it is now more abstract. The flexibility/clarity tradeoff is a common problem with modeling.

Notes:
1.The possible AtomTypes are combinations of Metal, NonMetal, Metalloid, TransitionMetal, Alkali, Alkaline, Halogen, NobleGas, Lanthanide, Actinide, HeavyMetal. This allows that there can be multiple types to define a single Atom. The model can now be easily extended if new types are needed.

Alternate Proposal

There were some questions about mixtures and compounds, and the following information was received. This is an explanation of the breakdown of matter.

An simple form of the drawing was done using the information about matter, although not all types of matter are shown on the drawing.

Note that this drawing is equivalent to the first drawing, except that the functional commonality of having children is replicated in each type of matter (ions and molecules). It is recognized that Atom Group is an artificial entity, but may be useful to reduce duplication.

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