Atomic number is calculated by the number of protons present in atom. But the atomic mass is calculated by the cobine calculated number of protons and neutrons present in an atom.foe ex-
oxygen(o) has 8 protons so the atomic number of O is 8 but the atomic mass of O is 16 because there are 8 neutrons in the atom.
Atomic Number: Number of PROTONS in an atom.
Atomic Mass: Number of PROTONS and NEUTRONS in an atom.
Mass Number: Number of PROTONS and NEUTRONS in an atom.
Atomic mass is equal to the total weight of an atom. Because most of the weight of an atom is due to the protons and neutrons (electrons don't weigh much), atomic mass is usually found by adding the number of protons and neutrons.
Atomic number and atomic mass are both numbers associated with atomic structure. Atomic number is important as it is the criteria used to arrange elements in the periodic table, a tool used extensively by chemists to study the properties of the elements.
Atomic number is also called proton number and is the number of protons in the nucleus of an atom. It is also equal to the number of electrons that orbit the nucleus. Electrons are the negatively charged particles in an atom.
The relative atomic mass of an atom is the mass of that atom calculated relative to one-twelfth of the mass of an atom of Carbon-12. It is sometimes referred to as the atomic weight of an atom but this is the incorrect term – mass should always be used. Relative atomic mass refers to the added numbers of protons and neutrons in the atom as electrons have only negligible mass. So, for example, the relative atomic mass of oxygen is 16, the atomic number of oxygen is 8; it has 8 protons and 8 neutrons and 8 electrons.
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