The Newlands' Law of Octaves was applicable only for elements up to magnesium.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

Atomic mass of $\mathrm{Cl}=35.5\mathrm{u}$ and that of $\mathrm{I}=127\mathrm{u}$. According to Dobereiner's triad rule, atomic mass of $\mathrm{Br}$ will be________$\mathrm{u}.$

Round off your answer to the nearest integer.

Dobereiner's law of triads is not applicable to