answersLogoWhite

0


Best Answer

Because their atomic masses are so precise and small that they can't be.

User Avatar

Cheyanne Tremblay

Lvl 13
1y ago
This answer is:
User Avatar
More answers
User Avatar

Wiki User

8y ago

There are two reasons.

First, each element has different isotopes each with a slightly different Atomic Mass, and these isotopes make up different fractions of the total population of each element.

An atomic mass of an element is therefore a weighted average considering all isotopes and their relative abundance.

As an example lets consider an imaginary element of atomic number 216. Let say that this element has isotopes of mass 501, 502, 503, 504, 505 and 506. Lets also say that out of 100 atoms

90 will be 501

5.. will be 502

2.. will be 503

1.. will be 504

1.. will be 505

1.. will be 506

to get an average... (90x501 + 5x502 + 2x503 + 504 + 505 +506)/100

= (45090 + 2510 + 1006 +504 + 505 + 506)/100

= 501.21 is the weighted average and will be the published atomic mass of the element, even thought it is not a whole number.

Secondly, and more fundamentally, there is something called binding energy which keeps the mass of even an individual nucleus from being a whole number (except for the carbon-12 nucleus, which by definition has a mass of exactly 12). This is the energy that holds the nucleus together, and it comes from converting a small part of the mass of the nucleons in the nucleus into energy. The highest binding energy per nucleon (and thus the lowest mass per nucleon) occurs around iron or nickel, and these nuclei are therefore slightly "light" compared to what you'd expect from simply counting the protons and neutrons.

(Finally, there's one more factor: except for hydrogen-1, each nucleus is a mixture of both protons and neutrons, which do not have exactly the same mass: the neutron is heavier by about 0.05%.)

This answer is:
User Avatar

User Avatar

Wiki User

12y ago

Because they are the average mass of an element compared to1/12 the mass of one atom of carbon-12. Average mass is used as if a sample has more than one isotope, they won't be of the same mass.

Eg chlorine has two naturally occurring isotopes: 75.53% is Chlorine-35 and 24.47% is Chlorine-37.

So ((35x75.53)+(37x24.47))/(75.53+24.47) =35.4894 =35.5 - Ar of Cl

This answer is:
User Avatar

User Avatar

Wiki User

12y ago

Because their atomic masses are so precise and small that they can't be.

This answer is:
User Avatar

Add your answer:

Earn +20 pts
Q: Why aren't the atomic masses of the most elements whole numbers?
Write your answer...
Submit
Still have questions?
magnify glass
imp
Related questions

Where are the proton and nuetron located on the periodic table?

In modern periodic tables, they arent; in order to find the number of neutrons in an atom you must subtract the atomic number (the number of protons) from the atomic mass (rounded to the nearest whole number). In older ones (from the 1930s), neutrons are listed as Element 0, but outside of very extreme environments (specifically, the core of a neutron star), that element simply does not exist, so it's no longer on the table.


What can you do if the fraction you have can not be easily be converted?

if your numbers arent whole numbers then multiply them out until they are whole numbers that are easier to work with.


Two different masses are they falling at the same speed?

they arent falling at the same speed because gravity is stronger with a heavier object


How do you know if you were born with the power to bend the elements?

sorry to burst your bubble but......you just arent


What is a typical number on a stem and leaf?

ther usually arent numbers on leafs look on jerseys 4 numbers


Where can you find the answers to the even numbers in the glencoe geometry textbook?

You can find the answers to the even-numbered problems in the back of the Glencoe Geometry textbook. The answers are usually located in the section designated for solutions or at the end of the chapter. If you can't find them in your edition, you may need to ask your teacher for assistance.


Why does the periodic table include elements that arent found naturally?

Because it is intended to represent all known elements, not only those which exist in nature.


How do you find the number of neutrons in an atom if that number is not told to you?

if you arent given the atomic numbert for an element - where could you find it?


What if you have a triangle with no number and is trying to find the area?

measure it with a ruler if there arent any numbers...


Why is atmosphere a mixture and not a compound?

Because the elements in the air arent bonded chemically, they are just literally mix together.


WHAT 11 equals 89?

nope. 11 dont equal 89. those numbers arent close at all duhhh


Is counting numbers whole numbers?

Whole numbers are 1,2,3,4..etc frations decimals and other numbers arent. Whole numbers include 0, counting numbers do not. Counting Numbers are also sometimes referred to as Natural Numbers. But the above answer is correct in that none of these sets: Counting, Whole and Integers include fractions or decimals.