Why atomic masses are not whole number?

Question

Please tell about it using isotopes.
Thank you so much!

Answer 1

The atomic mass is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance.

Example :the two principal isotopes of chlorine have atomic masses very nearly 35 and 37 and occur in the approximate ratio 3 to 1, so the atomic weight of chlorine is about 35.5

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.

Answer 2

There are two issues.

1. The average atomic mass of a element is the result of there being several isotopes in different proportions. A large sample of hydrogen would contain mostly H(1) which has one proton and very small amounts of H(2) which has one proton and one neutron, and H(3) which has one proton and two neutrons. So the average atomic mass would be the found by multiplying the proportions of these isotopes by 1, 2, and 3 respectively.

2. Also the masses of the proton and the neutron are not equal. The neutron is slightly heavier than the proton. So even if you had a sample of an element that was all one isotope it would not have a mass that was a perfectly whole number.

Some people wonder if the mass of the electron makes up for the deficiency in the proton's mass. After one form of radioactivity is when a neutron decays into a proton and an electron. However the mass of the neutron is more than a proton and electron combined. Some of this comes from the loss of energy during that decay according to Einstein's equation E=MC^2 but I'm not sure if that accounts for all of the difference.

Answer 3

[u] is convenient because one hydrogen atom has a mass of approximately 1 u, and more generally an atom or molecule that contains n protons and neutrons will have a mass approximately equal to n u. (The reason is that a carbon-12 atom contains 6 protons, 6 neutrons and 6 electrons, with the protons and neutrons having about the same mass and the electron mass being negligible in comparison.) This is an approximation, since it does not account for the mass contained in the binding energy of an atom's nucleus; this binding energy mass is not a fixed fraction of an atom's total mass. The differences which result from nuclear binding are generally less than 0.01 u, however. Chemical element masses, as expressed in u, would therefore all be close to whole number values (within 2% and usually within 1%) were it not for the fact that atomic weights of chemical elements are averaged values of the various stable isotope masses in the abundances which they naturally occur. [1] [For example, chlorine has a atomic weight of 35.45 u because it is composed of 76% Cl-35 (34.96 u) and 24% Cl-37 (36.97 u)].

Answer 4

Some atoms have more neutrons than protons, and therefore the weight is not a whole humber.

One proton weighs, ahh... something really strange. 1.14 x 10 to the 23 I think. That is the weight for C-12. However, for examble, C-14 exists, etc. which is an isotope. Therefore, the 2 extra neutrons would add some sort of extremely extremely small weight to the atom.

Anyways, so it's absured to think that the masses would be whole numbers in the first place, to begin with...

Answer 5

The atomic mass includes the number of neutrons. You can have one isotope, for example, carbon 12 that has 6 protons and 6 neutrons. Or you can have carbon 14 that has 6 protons and 8 neutrons. These are two different isotopes of carbon.

They average the different atomic masses of all the isotopes, weighted by the abundance of each.

Good luck on the rest of your homework.

Answer 6

If the # of protons are same and if they differ in # of neutrons then this is an called isotope. Take the average of all the mass number and that's the answer the atomic masses are in decimals.