Elements display periodicity ("Skeletal chemistry" 2 of 9)
"That we understand the origins of periodicity in terms of some rather simple ideas about how electrons arrange themselves around nuclei so as to achieve the lowest energy subject to certain constraints (ie the Pauli principle) means that we understand the personalities of the elements. Chemistry deals with entities that have personalities rather than their component parts, and it is right, I think, to present systematic as a story of the interaction of personalities."
Periodic Table
This is a very nice Periodic Table from Germany. It uses images to represent the relative sizes of both atoms and ions. It also helps differentiate between metals and non-metals using colors (or grayscale on one version), which helps establish the "personalities" Atkins describes.
Atoms and Matter (K-2)
While the nucleus in this Play-Doh model of the atom is of course way too big, representing the electrons as a continuous cloud shell is a nice first model to build on.
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Scaling an Atom
This activity uses a pin head to represent the nucleus, and a speck of powder to represent the electron cloud. It helps correct for the scale problems of the Play-Doh model.
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M&M® Model of the Atom: Edible Subatomic Particles
To understand periodic trends it is helpful to know about the relationship between the number of protons, electrons, and electron shells in the atom. It's better to think of the electrons as a cloud, and use this Bohr model just as an accounting system.
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Trading Places
The idea that copper ions can replace iron atoms starts to get at the relationships between the elements -- including the hierarchies that show up in things like the metal activity series.
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"Skeletal chemistry" article
This is one of the nine central ideas that Peter Atkins lays out in his 2005 article, "Skeletal chemistry." Each of the other ideas has its own list in SMILE.