When the system being studied is an ion, the charge, n, on the ion must be supplied by CHARGE=n. For cations n can be 1, 2, 3, etc.; for anions -1 or -2 or -3, etc. Examples of various charged systems are given in the Table below.
If CHARGE=n is not present, the charge required by the
Lewis structure will be used.
If CHARGE=n is present, including CHARGE=0, that charge will be used, unless
it is in conflict with the Lewis structure, in which case the job will be
stopped.
If both GEO-OK and CHARGE=n
are
present, that charge will be used, unless it is in conflict with the Lewis
structure, in which case the charge required by the Lewis structure will be
used. (This option is not useful, it is equivalent to CHARGE=n
being absent)
In cases where the charge supplied is in conflict with that required by the Lewis structure, the Lewis structure will be printed. That, together with the printed charged sites, will allow the correct charge to be determined.
Table:
Use of CHARGE=n|
Ion |
Keyword |
Ion |
Keyword |
|
|
|
|
|
|
NH4+ |
CHARGE=1 |
CH3COO- |
CHARGE=-1 |
|
C2H5+ |
CHARGE=1 |
(COO)= |
CHARGE=-2 |
|
SO4= |
CHARGE=-2 |
PO4-3 |
CHARGE=-3 |
|
HSO4- |
CHARGE=-1 |
H2PO4- |
CHARGE=-1 |