Question

Is atomic mass the sum of the number or mass of protons and neutrons.

If it is sum of number , then why is it called atomic MASS

And if it is sum of mass then how do we know the no of neutrons and proton sin the atom.

Answer 1

An element’s atomic mass (A) is the sum of the number of protons and the number of neutrons. The small contribution of mass from electrons is disregarded in calculating the atomic mass . This approximation of mass can be used to easily calculate how many neutrons an element has by simply subtracting the number of protons from the mass number. Protons and neutrons both weigh about one atomic mass unit or amu. Isotopes of the same element will have the same atomic number but different mass numbers. Atomic Number

Neutral atoms of an element contain an equal number of protons and electrons. The number of protons determines an element’s atomic number (Z) and distinguishes one element from another. For example, carbon’s atomic number (Z) is 6 because it has 6 protons. The number of neutrons can vary to produce isotopes, which are atoms of the same element that have different numbers of neutrons. The number of electrons can also be different in atoms of the same element, thus producing ions (charged atoms). For instance, iron, Fe, can exist in its neutral state, or in the +2 and +3 ionic states.