Is the number of protons in the nucleus of an atom, which identifies what the element is.

the number of protons and neutrons in the nucleus of an atom (the weight) identify that element’s

atoms of an element with different numbers of neutrons are called

atomic number

mass number

 isotope

Explanation:

1 . Atomic number ,For neutral atom , the value for atomic number equals the number of protons , and it helps to define the identify of an element .

2. Mass number , For neutral atom , the summation of the number of protons and the number of neutrons , together gives the value of  mass number .

3. Isotopes , are the substance , where the in a specific element , the number of neutrons are different .