Question

among the following elements F,Cl, Br and I which does not fit in a triad

Answer 1

F doesn't fit the trait

As both br and cl come in halogen grop of traids

Answer 2

In the history of Periodic Table of Elements, Early classification was done by Döbereiner. He gave his classification as Group of three Traids.

His full name was Johann Wolfgang Döbereiner.

According to him, Three elements were took together and The central element had mass that was mean of the first 2.

Example of his Traid :

Li (Lithium) -> {Mass Number} 6.9

Na (Sodium)

K (Potassium) -> {Mass Number} 39

Then the mass of Na will be Equal or Roughly same as : -

$\frac{6 + 39}{2}$

$\Longrightarrow\frac{45}{2}$

$\Longrightarrow\:23$ {Approx}

Now, We are given with

Flourine

Chlorine

Bromine

Iodine.

According to his Traids, Chlorine Bromine and Iodine are a traid

Hence F or Flourine doesn't fit.

Thanks!