1. Symmetry Summary
GLY 4200
Lab 5 - Fall, 2012

2. Definitions
Motif: the fundamental part of a symmetric design that, when repeated, creates the whole pattern
Operation: some act that reproduces the motif to create the pattern
Element: an operation located at a particular point in space

3. 2-D Symmetrical Pattern

4. Symmetrical Pattern
A pattern consisting of two motifs

5. Symmetrical Pattern
is the symbol for a two-fold rotation, known as a diad

6. 180 Degree Rotation
Rotate in two steps

7. Three Fold Rotation
360o/3 = 120o rotation to reproduce a motif in a symmetrical pattern
is the symbol for a three-fold rotation, known as a triad

8. N-Fold Rotations
Respectively, 360o, 180o, 120o, 90o, and 60o

9. Reflection Reflection across a “mirror plane” reproduces a motif
is the symbol for a mirror plane

10. Inversion
Inversion through a center to reproduce a motif in a symmetrical pattern
= symbol for an inversion center

11. Lab Exercise For lab, examine each object Report all symmetry
For rotation, the fold and number of each type of rotational axis present
Example: 1A4, 2A2
For reflection, total number of mirror planes present, if any
For inversion, yes or no (does it have a center or doesn’t it?)

12. Results
Keep a copy of your results for next week’s lab – you need to turn in one, and have one copy for lab 6