What is the mass number of an element?
A. Mass number is the atomic mass of a particular isotope.
B. Mass number is the mass of the most abundant isotope.
C. Mass number is the number of protons in the nucleus.
D. Mass number is the mass of the protons in the nucleus.

Question

What is the mass number of an element?
	        A.	Mass number is the atomic mass of a particular isotope.
 		B.	Mass number is the mass of the most abundant isotope.
 		C.	Mass number is the number of protons in the nucleus.
 		D.	Mass number is the mass of the protons in the nucleus.

sweetburger · Answer

Why do none of these seem correct. I thought it was the average mass of all known isotopes.

somy · Answer

all the choices are ridiculous to be honest 
only B kinda makes sense @sweetburger

ipwnbunnies · Answer

What. .-.  Mass number is the number of protons and neutrons in the nucleus.

abhisar · Answer

Mass number is the average mass numbers of all the isotopes. But it's always close to mass number of the most abundant isotope.
For example mass number of Cl-35 is 35 and that of Cl-37 is 37, but in general mass number of chlorine is taken as average of two which is 35.5, now we can see that it is quite near to mass number of chlorine-35 which is more abundant than Cl-37

zab505 · Answer

Which one would it be?

matt101 · Answer

I think B would be your answer here. It is the most reasonable of all the answers, but I agree with the others that it is not 100% correct.

When you do calculations though, you generally round the mass to the nearest whole number, which is typically the most abundant isotope anyways. Maybe that's what they're getting at...

zab505 · Answer

Thank you all very much!