CPK® Atomic Models, Nitrogen Atom, Aromatic-5

CPK® Atomic Models, Nitrogen Atom, Aromatic-5

Item# Description U.S. List Price Quantity
67-6825 CPK® Atomic Models, Individual Atom, Nitrogen, Aromatic-5
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Harvard Apparatus CPK® Atomic Models are sold three ways:

1. Individual Atomic Models, Connectors, and Accessories. These are specified on the following pages.

2. Sets for Specific Purposes

3. Assembled Molecular Structures. It is often more convenient to buy pre-assembled molecular structures. There is a large selection of these on the following pages.

Harvard Apparatus is always ready to quote for the custom assembly of all types of molecular structures.

Specifications and Assembly


1.25 cm/Å. Large enough to maintain high accuracy, yet small enough so that macromolecules are not unwieldy. For example, a model 20 x 40 x 100 Å can be built on a table top.


Bond Angles ±0°30’; Covalent radii ±0.01Å; van der Waals radii ±0.03Å. These are as they occur in most biomolecular structures, and these data agree generally with those published by Corey & Pauling. However, several changes reflecting recent observations have been incorporated.


Less than 1.0 gram/ml for a molecule as a whole. For maximum strength with minimum weight, the atoms are hollow. Except for hydrogen, they are injection-molded in Implex, a hard and durable modified acrylic polyester. Hydrogen has an elastically-compressible polyethylene shell.


Atoms and connectors are easily identified since each component is color-coded. The color cannot be worn away since it is an integral part of the plastic. Further, atom surfaces are satin-finished so that they can be lighted easily for vivid photography to illustrate journal articles.

Restricted Rotation

The rotation of certain atoms may be prevented with a special keyed link, see 67-7039 Connector Link, Locking on following page. The rotation of tetrahedral carbons in C-C bonds may be hindered with a special carbon link to produce the three-fold rotational potential

characteristic of such bonds, see 67-7047 Connector Link, Carbon on following page.

Hydrogen Bonding

Linear and non-linear bonded hydrogen species provide functional H-bonds to the appropriate species of nitrogen and oxygen. H-bond distance is adjustable.

Special Atom Species

A user may construct additional atom species not offered as regular CPK Atomic Models and use them with the regular CPK Atomic Models by attaching the 67-7088 Socket. This Socket takes all seven of the connector links offered on the following page.

Assembling or Taking Apart CPK® Atomic Models is Easy.


A Connector Link is placed in the well on the end of the handle of the 67-7120 Construction Tool. The Connector Link is then pressed into the female socket of the atom. The second atom is simply pressed onto the first with a slight twist, and the bond is made.

Taking Apart

To remove a Connector Link, the forked end of the 67-7120 Construction Tool is slipped around the center groove of the link, and the tool is pried upward.

The atoms are held together with great tenacity. A force of 5 to 7 kg is required to separate them. This force is readily furnished by the levering blade of the 67-7120 Construction Tool.

The marked superiority of the CPK® Atomic Models derives largely from Dr. Koltun’s Connector Links. His analysis of the engineering problems involved led him to combine new plastic materials with innovative link designs which satisfy four critical requirements simultaneously.

Since bond distances and angles for particular atoms are known to vary even in similar structures, two special links, in addition to the standard link, are provided to increase or decrease the normal bond distance by +0.08Å or -0.05Å.

A special ‘gluing’ link is also available for permanently connecting atoms at standard bond distances.

The various link types are color-coded to aid identification.

Nitrogen, Aromatic-5

For use in five-membered rings such as in 67-8266 Imidazole or in positions 7 and 9 in 67-8262 Purine. Covalent radius 0.68Å to atoms within ring and covalent radius 0.73Å to atoms outside ring; bond angle 108° between atoms within ring and 126° between single-bonded atom outside ring and double-bonded ring atoms; symbol ‘5’ stamped on one inner face. Partial double-bond sockets notched. 67-7112 Amine Cap converts 67-6825 Nitrogen, Aromatic-5 to azo nitrogen. For details of the 67-7112 Amine Cap see page P12. Blue.
Bond Angle108
Covalent Radii Double Bond0.68 (partial)
Covalent Radii Single Bond0.73
Scale Metric1.25
van der Waals Radii1.70