Question

what is a Dobereiner's triads ? Explain​

Answer 1

Answer:

He proposes different traids depending upon many properties like increasing atomic mass, similar in properties and the atomic mass of the middle element is the arithmetic mean of atomic mass of first and third element.

For example:- Consider the elements Li, Na and K



They have some chemical properties i.e.

all are metals

all react with water to form alkalis

all have valency-1

 Atomic mass of middle element (Na) = (7+39)/ (2) = 23

             

all are metals

oxides of then are alkaline

all have valency2.

Atomic mass of Sr = (40 + 137)/ (2) = 88

 

 All are non-metals

All react with water of form acids

All have valency1

 Atomic mass of Br = (35.5 + 127) /(2) = 80

Limitation- He failed to arrange all known elements in form of triad.