In atoms, the atomic number represents the number of protons in the nucleus of an atom. It is denoted by the letter "Z." The atomic number defines the identity of an element because each element has a unique number of protons in its nucleus.
The atomic mass number, on the other hand, represents the total number of protons and neutrons in the nucleus of an atom. It is denoted by the letter "A."
In a neutral atom, the number of protons (Z) is equal to the number of electrons, as atoms are electrically neutral. However, the atomic mass number (A) is not necessarily equal to the atomic number (Z) because it includes the mass of both protons and neutrons.
Therefore, the atomic number (Z) cannot be greater than the sum of protons and neutrons (A). It will always be equal to or less than the atomic mass number (A). If the atomic number were greater than the sum of protons and neutrons, it would imply the presence of additional particles in the nucleus, which is not the case.
To summarize, the atomic number (Z) represents the number of protons in an atom's nucleus, while the atomic mass number (A) represents the total number of protons and neutrons. The atomic number cannot exceed the sum of protons and neutrons because it defines the element's identity and remains constant for a specific element.