Atoms for molecular structures Bond length scale 1 to 2.6x108 Atom Length scale 1 to 1.7x108

.................Valance....Radius (pm)....Radius of ball (mm)......Angle (degrees).....CPK colour Hydrogen..H.....1........37...................6.25.........................n/a.....................................White Carbon......C.....4........77.................13.00........................109.5..................................Black Nitrogen....N.....3........70.................11.82........................107 (in Ammonia)...............Blue Oxygen.....O.....2........66.................11.15........................104 (in water).....................Red

..............................Length (pm).....Length (mm) Single bond..................153.5............40 Double bond.................133.9...........35

Atom radius https://www.sizes.com/natural/atoms.htm Bond angles https://www.chemguide.co.uk/atoms/bonding/shapes.html#:~:text=Four%20electron%20pairs%20arrange%20themselves,bond%20angles%20are%20109.5%C2%B0. Carbon is close to a tetrahedral (equilateral 3 sided pyramid). N and O are variations on this. Angles change slightly in real atoms depending on the molecular polarization and other stress. 3D prints are fixed but bonds can bend if a flexible material like TPU is used. Bond lengths https://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s12-08-properties-of-covalent-bonds.html Scale your model to fit your connectors The connector holes are a tight fit for the 3 mm radius clear tubes I have used. Rescale your model before printing to the radius of the connectors you use. Drinking straws or cocktail sticks should work well. Or print your own connectors but, 3D prints are never very beautiful. If you make the holes too small they are easy to drill out.