What is the atomic mass of an element equal to atomic number or number of protons?

Answer 1

Answer:

The Atomic Mass is NOT equal to both 'atomic number' and 'number of protons .

The atomic mass of an element is by approximation equalto, but not exactly, the sum of protons and neutrons in the nucleus of the atom.

The number of protons is given by the atomic number, not atomic mass.

So, only the atomic number of an element AND the number of protons are equal. The atomic mass is also depending on the number of neutrons.

More explicative:

The atomic mass of an element refers to a particular isotope of that element, and is equal to the sum of the protons and neutrons in the nucleus of atoms of that isotope.

For example, carbon-12 atoms have 6 protons and 6 neutrons, while carbon-14 atoms have 6 protons and 8 neutrons.

Atomic weight, which is shown on the Periodic Table is a weighted average of the atomic masses of all the different isotopes of each element.

For example, the atomic mass of C-12 is 12.0000 a.m.u. and the atomic mass of Carbon is 12.0107(8) g/mol

From the Periodic Table you can only tell the number of protons in the atoms of all of the isotopes of a given element, because the number of protons defines the element, and is the element's atomic number. However, you cannot tell the number of neutrons from the Periodic Table. You would have to look up the atomic masses of all the isotopes of each element in some sort of reference. The atomic number of an element is equal to the number of protons in the nucleus of an atom.