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Why is the atomic mass of an element not usually given as a whole number even though each individual atom of the element has a whole number of protons and neutrons?
It's because of electrons, they have a relative mass of 1/1836
Why is an element's atomic mess not listed as a whole number on the periodic?
Because it is an average of the masses of the isotopes of the element, each of which has a different atomic mass (not mess!)
What is the mass number of cadmium?
Cadmium is a metal element. Mass number of it is 112.
Can mass only be a whole number?
No, it cannot. A whole number is a quantity without units - a pure number. A mass of 1 pound is a whole number of pounds but it is 0.45359 kilograms: not a whole number, or 453.59 grams, again not a whole number.
Why is an elements atomic mass not listed as a whole number on the table?
There are two main reasons. The first is that the masses of protons and neutrons are not 1 unit but slightly greater. The mass of an atom is the mass of a whole number of protons, a whole number of neutrons as well as the same number of electrons as protons. Overall, therefore, the mass should be greater than the number of protons and neutrons (electrons have very little mass). But some of the mass is converted to energy which is used to hold the positively charged nucleus together. As a result the mass of carbon12 is an exact whole number and that is the only element for which that is true.The second, and possibly more relevant reason is that most atoms are found in the form of isotopes which have different numbers of neutrons and so different masses. The atomic mass listed for an element is an average of the masses of all these isotopes, weighted together according to their abundance of earth.
