(i) Alkali metal group (Dobereiner’s Triad)
Element of the triad | Symbols | Atomic masses |
1. Lithium | Li | 7 |
2. Sodium | Na | 23 |
3. Potassium | K |
39 |
(ii) Alkaline earth metal (Dobereiner’s Triad)
Element of the triad | Symbols | Atomic masses |
1. Calcium | Ca | 40 |
2. Strontium | Sr | 88 |
3. Barium | Ba |
137 |
(iii) Halogen Group (Dobereiner’s Triad)
Element of the triad | Symbols | Atomic masses |
1. Chlorine | Cl | 35.5 |
2. Bromine | Br | 80 |
3. Iodine | I |
127 |