The atomic number (Z) represents the number of _____ present in the nucleus of an atom.
Atomic number of an element is the number of _______ present in the nucleus.
Consider the following statements:
1. The number of protons in the nucleus of an atom of a given element is called the atomic number of that element.
2. Mass number of an atom is defined as the sum of number of protons and neutrons present in the nucleus of an atom.
3. Atoms of an element that have the same atomic number (Z) but different mass number (A) are called isotopes.
Which of the above statements is incorrectly stated?