Why is the atomic mass of an element not given as a whole number when the protons and neutrons are whole numbers?

Answer 1

It's the electrons that throw it off.

Answer 2

The Atomic Mass of an element is calculated by averaging the masses of its isotopes based on their abundance in nature. Since isotopes have different numbers of neutrons, the resulting atomic mass is not a whole number. The weighted average accounts for these fractional values.

Answer 3

When you determine the atomic weight of an element you are taking the average weight of a mole of such atoms. Mole = 6.022 × 1023 of anything. (A mole is a measurement of "amount", so it can refer to anything, but is most commonly used with atoms).

Most elements have more than one isotope, that is, there is some variance in the number of neutrons they contain. Both the protons and neutrons provide mass but only the protons provide chemical and physical characteristics (to any degree needed for this question that is).

Therefore, when we weigh a mole of any element we are not getting a sum of exact multiples of a single mass but also a few slight variants as well due to the isotopes. When we take the average of such a sum what we are getting is therefore a weighted average, dependent on the percent abundance of all isotopes.

Answer 4

Atomic mass is the total mass of protons, neutrons and electrons in a single atom.

The reason electrons are usually discarded is because they are about 1/1837 the size of either a proton or neutron.

Answer 5

An element's atomic mass is not an integer (a whole number) because it is the average mass of all of the element's isotopes (elements that have different amounts of neutrons effecting the mass number of an element). For example, oxygen has 16.01 as its atomic mass. Oxygen has an isotope with 8 neutrons but also has a less rarer isotope with 9 neutrons giving mass numbers of 16 and 17. The atomic mass is slightly pulled over closerto 17, but since 16 in the mass number is more common, the atomic mass is much closer to 16. That there creates the average in the atomic mass.

Answer 6

Atomic mass is simply the mass of a single atom of a particular element. (It varies sometimes in elements due to isotopes) The atomic mass doesn't tell us the number of neutrons or protons by itself. Rather, one needs to know the atomic number of the element in question.

To find the number of neutrons, you need to subtract the atomic number from the atomic mass. The difference is the number of neutrons (it should be the rounded whole number). Protons are not to be found in the atomic mass.

Answer 7

Because protons are positive and electrons are negative.

Answer 8

because electrons are too light to be counted and the weight of the body mostly depends on the no. of protons and electrons.

Answer 9

Atoms lose or gain electrons in the process of becoming positive or negative ions. The number of protons can only change if the nucleus is fissioned or fused, producing new elements.

Answer 10

The sum of the protons and neutrons in the atoms of an isotope is called the mass number of that isotope.