periodic trends...help please!

i'm making a 3D model of the table for my chem class and we have to explain the way that we show the periodic trends (as many as possible). I've already figured out the trends for atomic radius, ionization energy, electron affinity, and electronegativity, but i just can't see the trends in some others. Any help with understanding the trends of covalent radii, ionic radii, boiling point or density? Thanks! (( stakey321@hotmail.com ))

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