What is the atomic number of hydrogen in the Mendeleev's periodic table?

1

The correct answer is option (1) 1.

In Mendeleev's periodic table, the atomic number of hydrogen would still be 1.

The atomic number of an element represents the number of protons found in the nucleus of its atoms. For hydrogen, this number is 1, regardless of the version of the periodic table being used. Therefore, the atomic number of hydrogen remains 1, irrespective of the periodic table's version.