What will be the formula of '$M$' nitrate based on the given Lothar Meyer curve?

How many periods and groups are there in Mendeleev's periodic table?

State whether the following statements are true or false:
$(i)$ The chart of elements presented by $Courtois$ could predict the stoichiometry of oxides of some metals.
$(ii)$ $Li, Na, Rb$ are known as $Döbereiner's$ triads.
$(iii)$ In $1863$,$Newlands$ classified the $56$ discovered elements into $18$ groups.
$(iv)$ $Mendeleev's$ periodic table is based on the atomic number of elements.

Which of the following is a Dobereiner's triad?

Fill in the blanks given below:
$(i)$ The first scientist to think about the properties of elements was ......... .
$(ii)$ The relationship of properties of elements suggested by Dobereiner is known as ........... .
$(iii)$ The Law of Octaves was proposed by the chemist ......... .
$(iv)$ The first periodic table was constructed by .......... and .......... .

What is the basic difference in approach between the Mendeleev's Periodic Law and the Modern Periodic Law?