Hii madhu....
well to understand the compound by mere look is some what an experience that comes with experiments ...
Appearance of compound details
The compound will most likely be in solid form. Note the color and shape of the crystals. Ionic compounds formed from the representative elements tend to be white or colorless, while ions of transition elements tend to be colored. The following is a table of the colors of metal ions in solution with NO3-.
| Ion | Color |
| Co2+ |
rose |
| Co3+ |
violet |
| Cr3+ |
violet |
| Cu2+ |
blue |
| Fe2+ |
pale green, pale violet |
| Fe3+ |
yellow-brown |
| Mn2+ |
pale pink |
| Ni2+ |
blue-green |
If you check this table i think you will next time identify the compound by just looking at it ....or atleast you will b able to know the cation involve ...