What is called relative atomic mass of an element?

The atomic mass of hydrogen

What is relative density?

Who showed that the atomic number of an element is a more fundamental property than its atomic mass and when?

The atomic number of an element X is 20 while the atomic number of an element Y is 24.What is the nature of the bond formed between X and Y?Give the electron-dot structure of the compound formed.

An atom has electronic configuration 2,8,7. What is the atomic number of this element?

Modern periodic tables is based on the atomic number of the elements . The experiment which proved the significance of the atomic number was