Cochranes of Oxford Molecular Models - Brief Instructions

Plastic balls with prongs for bond connections are used to represent the nuclei (atom centers) of various elements. Straws of various lengths are used to represent bonds.

Type of Atom	# of Prongs	Bond Angle (deg)	Color	Shape
H	1	-	White
C (sp3)	4	~ 109.5	Black
C (sp2)	3	~ 120	Black
C (sp1)	2	~ 180	Black
O (sp3)	2	~ 105-112	Red
O (sp3)	- or use a 4-prong tetrahedral center to show lone-pair electrons
O (sp2)	1	-	Red
O (sp2)	- or use a 3-prong (120 deg) center to show lone-pair electrons
N (sp3)	4	~ 107-113	Blue
N (sp3)	(one of the prongs will represent the lone-pair electrons)
N (sp2)	3	~ 120	Blue
N (sp2)	(two of the prongs will represent lone-pair electrons)
Halogens	1	-	Green

Use straws of various lengths to reprent bonds. Suggested straw lengths for several bond lengths are shown below. For more accurate models, the straws can be cut to scale (3 cm = 0.100 nm is a convenient scale).

C(sp3)-C(sp3)	0.154 nm	Longest Straw		C(sp3)-H	0.111 nm	Shortest Straw
C(sp2)-C(sp2)	0.134 nm	Medium Straw		C(sp2)-H	0.110 nm	Shortest Straw
C(sp1)-C(sp1)	0.121 nm	Medium Straw		C(sp1)-H	0.108 nm	Shortest Straw

To depict multiple bonds, the clear pegs () can be inserted on appropriate atoms to attach extra straws for bonds -- two straws total for double bonds; three for triple bonds.