The mass number and atomic number are two fundamental properties used to describe atoms. Here's the difference between them:
Atomic Number: The atomic number (Z) represents the number of protons found in the nucleus of an atom. It defines the identity of an element and determines its position on the periodic table. Elements are arranged in ascending order of their atomic numbers. For example, hydrogen has an atomic number of 1, helium has an atomic number of 2, and so on.
Mass Number: The mass number (A) refers to the total number of protons and neutrons present in an atom's nucleus. It gives the approximate mass of an atom. Since protons and neutrons have similar masses, the mass number is roughly equal to the total number of nucleons (protons + neutrons). The mass number is usually written as a superscript to the left of the atomic symbol. For instance, helium-4 (4He) has a mass number of 4.
Now, regarding your second question, atoms with the same mass number do not necessarily have the same properties. While the mass number provides information about the mass of an atom, it does not define the atom's identity or its chemical properties. The chemical behavior and properties of an atom primarily depend on its atomic number, which is determined by the number of protons. Atoms with the same atomic number (same number of protons) belong to the same element and exhibit similar chemical properties. However, atoms with the same mass number but different atomic numbers are isotopes of each other. Isotopes have the same number of protons but different numbers of neutrons, resulting in slightly different masses. These isotopes may have different physical properties, such as varying stability, radioactivity, or nuclear behavior, but their chemical properties, which are determined by the atomic number, remain largely the same.