Lakhmir Singh and Manjit Kaur Solutions for Chapter: Periodic Classification Of Elements, Exercise 1: Questions Based on High Order Thinking Skills(HOTS)

$\mathrm{A}$, $\mathrm{B}$ and $\mathrm{C}$ are the elements of a Dobereiner’s triad. If the atomic mass of $\mathrm{A}$ is $7 \mathrm{u}$ and that of $\mathrm{C}$ is $39 \mathrm{u}$, what should be the atomic mass of $\mathrm{B}$?

$\mathrm{X}$ and $\mathrm{Y}$ are the two elements having similar properties which obey Newlands’ law of octaves. How many elements are there in-between $\mathrm{X}$ and $\mathrm{Y}$?

What was the Mendeleev’s basis for the classification of elements?

In the classification of the then known elements, Mendeleev was guided by two factors. What are those two factors?

Name two elements whose properties were predicted on the basis of their positions in Mendeleev’s periodic table.

The three elements predicted by Mendeleev from the gaps in his periodic table were known as Eka-boron, Eka-aluminium and Eka-silicon. What names were given to these elements when they were discovered later on?

Consider the following elements
$\mathrm{Na}, \mathrm{Ca}, \mathrm{Al}, \mathrm{K}, \mathrm{Mg}, \mathrm{Li}$
Which of these elements belong to the same period of periodic table?

Consider the following elements
$\mathrm{Na}, \mathrm{Ca}, \mathrm{Al}, \mathrm{K}, \mathrm{Mg}, \mathrm{Li}$
Which of these elements belong to the same group of periodic table?