What is atomic number?

What are atomic number and mass numbers ?

What is the atomic number and mass number of proton and tritium.

A positron is emitted by a radioactive nucleus of atomic number 90. What is the atomic number of the product nucleus ?

An atom baving mass number 40 has 20 neutrons in its nucleus. What is the atomic number of the clement?

The electronic configuration of transition element "X", is +3, oxidation state is [Ar]3d^(5) . What is its atomic number?