What are the common atomic radii used for chemical pictures?

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SUMMARY

The common atomic radii used for drawing chemical pictures primarily include half the covalent radii for ball-and-stick models, as noted by various users in the discussion. While there are no strict rules governing these representations, consistency is key. Many software programs adopt similar conventions, with "spacefill" models typically utilizing full covalent radii or slightly larger. The discussion emphasizes that these visual representations serve more for structural illustration rather than precise scientific measurement.

PREREQUISITES
  • Understanding of covalent radii and their application in molecular modeling.
  • Familiarity with ball-and-stick and spacefill models in chemistry.
  • Knowledge of visualization software used for chemical structures.
  • Basic principles of molecular geometry and representation.
NEXT STEPS
  • Research the differences between covalent radii and van der Waals radii in molecular modeling.
  • Explore software options for drawing chemical structures, such as ChemDraw or PyMOL.
  • Learn about the implications of using different atomic radii in chemical representations.
  • Investigate the role of molecular visualization in understanding electron densities and bonding.
USEFUL FOR

Chemists, molecular modelers, educators, and students interested in visualizing chemical structures and understanding the conventions of atomic radii in chemical illustrations.

somasimple
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Hi all,

What are the common atomic radii that are used for drawing chemical pictures?

Is it the ionic or calculated or?

Thanks.
 
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Whatever, as far as I am aware there are no set rules. There is some obvious logic that you can apply, but as long as your pictures are not drawn to be a scientific tool (like DNA models built by Watson and Crick) you don't have to pay too much attention to it. Just be consistent.
 
My program uses (for its default ball-and-stick mode) half the covalent radii. (vdW radii look a bit too chunky). Most programs use something similar. (To the extent I sometimes see papers with images that might have been made with my program, but I can't be sure) "Spacefill" models would be around the full covalent radius, or slightly larger.

It's not like the spheres in these pictures have much in the way of physical meaning; you're only drawing the structure.
If you want to say something about orbitals or bonding or electron densities, then that's what you plot, not ball-and-stick models.
 

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