An unknown element is found to contain 45 protons and an atomic mass of 64, what is its atomic number?

Answer 1

The atomic number gives the identity of the element and is always the number of protons, 45 = Rhodium = Rh

Each atomic number (element) can have varying numbers of neutrons, which is known as an isotope for that atomic number (element). The difference between the atomic mass and atomic number gives the number of neutrons, 64-45=19 neutrons. It happens to be that the only isotope of Rh has 19 neutrons and is given as ⁶⁴Rh

Higher atomic numbers can generally accommodate more numbers of isotopes. Funny, Rhodium only has one isotope. Can you come up with a reason why?

Answer 2

Atomic number = the number of protons. So the atomic number would be 45

Answer 3

the definition of atomic number is: the number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table

atomic mass is approximately equivalent to the number of protons and neutrons