| Default CPK | Modified CPK |
O - oxygen |
O - acidic |
 O
- non-acidic |
|
N - nitrogen |
N - basic |
|
N -
non-basic |
|
C - carbon |
C - backbone |
C - sidechain, R-group |
|
 Cl
- chlorine |
|
S - sulfur |
|
H - hydrogen |
|
 - unknown atom type |
|