In the Lothar Meyer curve,the descending position (next to the peak) is held by which of the following?

$Li, Na, K$ form a Dobereiner's triad. If the atomic masses of $Li$ and $K$ are $7$ and $39$ respectively,what will be the atomic mass of $Na$?

What were the important contributions of Mendeleev's periodic table?

On the basis of which property did Mendeleev arrange the elements?

Given below are two statements :
Statement $(I):$ According to the Law of Octaves,the elements were arranged in the increasing order of their atomic number.
Statement $(II) :$ Meyer observed a periodically repeated pattern upon plotting physical properties of certain elements against their respective atomic numbers.
In the light of the above statements,choose the correct answer from the options given below :

Who stated that the properties of elements are a periodic function of their atomic number?