Why is the atomic mass number considered an average?

Question

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Answer 1

Different elements, especially the heavier ones, may
have more or fewer neutrons than they might appear
to on the standard table of the elements.

The type of element is determined by the number
of PROTONS, not the the combination of protons
and neutrons.

Therefore, one proton plus one electron equals
on hydrogen atom. One proton plus one electron
plus one neutron is also a hydrogen item.

Atoms with different numbers of protons and neutrons
are called isotopes.

In any case, if you took a sample of, say hydrogen,
a small portion wouldd have more neutrons than you
expect and a different portion woul have fewer and
when you average it all out, you get the listed average.

Answer 2

Every element has a number of isotopes with the same number of protons, but different numbers of neutrons in the nucleus. The atomic mass number is an average of the atomic masses of these isotopes as they occur in nature. For the artificial elements, the atomic mass number is the mass of the most stable isotope produced.

Answer 3

Because different atoms have different isotopes or forms of the element which have different numbers of neutrons that alter the molecular weight. The atomic mass is an averge of these varying weights.

Answer 4

a million)The style of protons in a nucleus is named the atomic quantity and consistently equals the style of electrons in orbit approximately that nucleus (in a nonionized atom). subsequently, all atoms that have the comparable style of protons--the atomic quantity--are atoms of the comparable ingredient. 2)The atomic mass is the finished mass of protons, neutrons and electrons in one atom. 3)the finished weight of an atom is named the atomic weight. this is approximately equivalent to the style of protons and neutrons, with a sprint greater extra by ability of the electrons for nucleus.

Answer 5

Because of all the isotopes of the atom. They take the average.