neet 2020

Group of Li, Na, K are called 1. Metals 2. Alkaline earth metals 3. Inactive metals 4. Triad

Which of the following group of elements are triad 1. Na, Ne, k 2. Cl, Br, I 3. Li, Fe, Ni 4. C, N, O

Dobereiner arranged elements as 1. groups 2. periods 3. triads 4. All the above