What were the two main reasons that Dmitri Mendeleev's periodic table was more successful than Lothar Meyer's?

Next, Mendeleev began a text for inorganic chemistry (concerned with substances that are not organic, such as minerals), and the result, Principles__of Chemistry (two volumes, 1868–1870), would become the standard text for the field until early in the 20th century. His research for this book would also lead him to his most renowned work.

Explanation:

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.