The law of triads is applicable to a group of

State whether the following statements are true or false:
$(i)$ The first periodic table was proposed by Dobereiner.
$(ii)$ The law of octaves was proposed by Newlands in $1865$.
$(iii)$ Mendeleev was the first to propose the periodic law.
$(iv)$ Mendeleev named Eka-aluminium as Germanium and Eka-silicon as Gallium.

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

Write the drawbacks in Mendeleev's periodic table that led to its modification.

Explain the "Law of Triads" with examples.

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