Why is the realative atomic mass of an element not always a whole number?

Answer 1

They are not whole numbers because there are different isotopes of the elements. The atomic weight is the average based on the proportions that they occur in naturally. For example, hydrogen comes with a single proton, a proton + a neutron, and a proton plus two neutrons. The isotopes with the neutrons occur in very small amounts so the average weight is slightly greater than 1.

If the Atomic Mass is not a whole number, then that means it is an average atomic mass of all the element's isotopes' atomic masses.

Answer 2

because why no

Answer 3

The number of protons in neutrons in the nucleus of an atom is defined as atomic mass (also known as relative atomic weight). The average atomic mass for all the isotopes of an element is given as the element's atomic weight compared to carbon 12. Because it is an average, atomic weights are decimal numbers.

Answer 4

The atomic mass number's not always a whole number, because it's a weighted average of the masses of all of an element's atoms.

There are differences between the masses of atoms of the same elements, because the atoms can have different numbers of neutrons (isotopes!). The difference between the number of neutronsin each atom makes some atoms heavier than others. The difference in masses of all of the different atoms of an element, when all of the atoms' masses are averaged out, is what causes the atomic mass number to shift from being a whole number.

The other thing that causes the atomic mass to not be a whole number is the amount of each isotope of an element (atoms of the same element, but each with different numbers of neutrons). If one isotope is a lot more common than another isotope, the more common isotope is going to more heavily influence the average mass, because most of the element's atoms will have that mass.

For example, hydrogen has an atomic mass number of 1.008 amu. The reason that the number isn't a whole number is because hydrogen has different isotopes, with different numbers of neutrons. There's hydrogen with no neutrons (most common atom); hydrogen with one neutron; and hydrogen with two neutrons (least common atom).

So, based on the difference between the number of neutrons, and how much of each atom there is, the atomic mass number is weighted, and often does not end up being a whole number.

Hope it helps.

Answer 5

question 4 of pixl anyone? :)