Embibe Experts Solutions for Chapter: Periodic Classification of Elements, Exercise 1: Exercise

The number of elements known at present are

_____ group contains the member of the halogen family.

The longest period in the periodic table is-

Which of the following form strongest metallic bond?

The S.I unit of ionisation energy is-

What are the advantages of classifying elements in the periodic table?

Classify the given elements as metals, non-Metals and metalloids.
$\mathrm{Na}$, $\mathrm{O}$, $\mathrm{As}$, $\mathrm{Cl}$, $\mathrm{W}$ and $\mathrm{Te}$ 

A is a reddish-brown metal, which combines with ${\mathrm{O}}_2$ at $<1370 \mathrm{K}$ gives B, a black coloured compound. At a temperature $>1370 \mathrm{K}$, A gives C which is red in colour. Find A, B and C with reaction.