Answer:
The answer to your question is: 20
Explanation:
Atomic number is the number of proton and atom has. Each element has a specific number of protons, if the number of protons change, then this is a new element.
Mass number is the number of protons and neutrons and atom has.
Mass number = protons + neutrons
Data
Number of protons = ?
Atomic number = 20
Then,
atomic number = number of protons = 20
