Space-filling molecular models: Nitrogen expansion set

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Nitrogen typically forms three bonds with other atoms, but it also has one pair of electrons that don't participate in bonding and still occupy space. The three bonds and the lone pair electrons usually take the shape of a tetrahedron, but if the lone pair is near a double bond, it re-arranges to contribute to the double bond and the bonded atoms adjust into a planar triangle without breaking any bonds. So, the 3D structure of nitrogen compounds depends on where the lone pair is located. Nitrogen6 represents the tetrahedral form, while NitrogenSP21 shows the planar form. There are also double and triple-bonded nitrogens, but most of these apply to more complex compounds. Compounds with double-bonded nitrogens are often called diazo or other unusual names, use Nitrogen DB1 for this; the bottom socket represents the double bond, technically it doesn't rotate, but that's a complicated topic. Nitrogen can form a triple bond with carbon to create nitriles, which are also known as cyanides (popular among mystery writers). Elemental nitrogen in the air is also triple-bonded to itself. Use NitrogenTB1 for this. Nitrogen can also form four bonds, but that results in a positive charge. Use the corresponding carbon atoms for this, and choose the correct color (they're the same size and shape). See the starter set (http://www.thingiverse.com/thing:1720048), the carbon expansion set (http://www.thingiverse.com/thing:1730299), the aromatic expansion set (http://www.thingiverse.com/thing:1754393), halogen expansion set (http://www.thingiverse.com/thing:1730099), and the sulfur and phosphorous expansion set (http://www.thingiverse.com/thing:2350618) for additional useful elements. Printer settings: Da Vinci 1A printer Rafts: Doesn't matter Supports: Doesn't matter Resolution: 0.2 mm Infill: 10% Notes: Three perimeters work well.