Question

Law of Triads is applicable to which set of elements?

Answer 1

Law of triads

• In 1817 Johann Wolfgang Doebereiner arranged similar elements in groups of three and showed that their atomic weights were either nearly the same or the atomic weight of the middle element was approximately the arithmetic mean of the other two.
• These groups of three elements were called Doebereiner's Triads.

Some examples of triads:

Iron 55.85	Cobalt 58.93	Nickel 58.71	Atomic weights are nearly the same	Triad
Lithium 7	Sodium 23	Potassium 39	Mean $\frac{7+39}{2}=23$	Triad
Chlorine 35.5	Bromine 80	Iodine 127	Mean $\frac{35.5+127}{2}=81.25$	Triad
Calcium 40	Strontium 87.5	Barium 137	Mean $\frac{40+137}{2}=88.5$	Triad

The Law of Triads is applicable to the above-mentioned set of elements.