Chemistry - isotpic mass, atomic mass, mass number

[clairez93]

Homework Statement

The two isotopes of antimony have masses 120.90 and 122.90, with a relative abundance of 57.25% and 42.75% respectively. Using these figures, distinguish clearly between atomic mass, isotopic mass, and mass number.

Homework Equations

The Attempt at a Solution

I think atomic mass is the relative isotopic abundance which in our case would be

(0.5725)(120.90) + (.4275)(122.90) = 121.755

Would isotopic mass be simply 120.90 and 122.90?

Would mass number be the same as the atomic mass?

Some how I think I am wrong concerning the last two.

 

[lanedance]

i think mass number is the total number of protons & neutrons

the others sound reasonable, but its been a fair while since I've played with this stuff

 

[Blueshift5]

Your understanding of atomic mass is correct. It is the weighted average of the masses of all the naturally occurring isotopes of an element, taking into account their relative abundance.

Isotopic mass refers to the mass of a specific isotope of an element. In this case, the isotopic masses would indeed be 120.90 and 122.90 for the two isotopes of antimony.

Mass number, on the other hand, refers to the total number of protons and neutrons in the nucleus of an atom. It is often represented by the symbol A and is usually written as a superscript before the chemical symbol of an element. In this case, the mass numbers would be 121 and 123 for the two isotopes of antimony.

So, in summary, atomic mass is the weighted average of the isotopic masses of all the naturally occurring isotopes of an element, isotopic mass refers to the mass of a specific isotope, and mass number is the total number of protons and neutrons in an atom's nucleus.