[cshujas]

what is different between atomic mass and an atom's mass?

Please make me clear on above topic.

[Arkcon]

The question could mean many things -- can you give us the exact question?  Or maybe an example of what you mean in each case?  Or two results for the same element that give two numbers?

[cshujas]

As we know, atomic mass of Oxygen is 16. Again mass of an Oxygen atom is 16/6.022×10^23 g.

Also 1 mole atom Oxygen is 16 g. But 1 mole Oxygen = 6.022×10^23 number of Oxygen atoms.

What is the correlation between atomic mass and an atom's mass?

[Arkcon]

As we know, atomic mass of Oxygen is 16.

No.  Many periodic tables like to give an average mass of 15.999 for the element oxygen.  That's an average, taking into account the relative abundances of some lighter and heavier isotopes.

Again mass of an Oxygen atom is 16/6.022×10^23 g.

I don't know why this is significant.  But OK.

Also 1 mole atom Oxygen is 16 g.

Nope.  See above.

But 1 mole Oxygen = 6.022×10^23 number of Oxygen atoms.

The fact is true.  But I don't see why you say "But", because nothing in that statement refutes anything else.  Its not actually connected, you see.

What is the correlation between atomic mass and an atom's mass?

Check your textbook or class notes for the definition of each.  You may find the difference you'll need to answer this question properly.  You will need that come exam time, since they've asked you this specific question.

[cshujas]

according to Carbon scale,

atomic mass= actual mass of an atom / (1/12 the mass of an atom of carbon-12)

So, we can write,

atomic mass of Carbon = actual mass of a Carbon/ (1/12 the mass of an atom of carbon-12) =12

or,

atomic mass of Oxygen = actual mass of a Oxygen/ (1/12 the mass of an atom of carbon-12) = 16

Again, mass of a single Carbon is= 12/ 6.022×10^23 g
       
or,      mass of a single Oxygen is = 16/6.022×10^23 g.

Again, Atomic mass of an atom = Gram-atomic mass of an atom = 1 mole atom

Again 1 mole atom is = 6.022×10^23 number of atoms.

Now my question is that does atomic mass express for a single atom? If this, why do we calculate a single atom's mass this way?  (mass of a single Oxygen is = 16/6.022×10^23 g.)

I am very confused with it, please give me a clear conception.

[betterbesafehero]

Now my question is that does atomic mass express for a single atom? If this, why do we calculate a single atom's mass this way?  (mass of a single Oxygen is = 16/6.022×10^23 g.)

I am very confused with it, please give me a clear conception.

The atomic mass is defined as the mass of an atom, which can only be one isotope at a time and is not an abundance-weighted average as in the case of atomic weight. In the case of many elements that have one dominant isotope, the actual numerical similarity/difference between the atomic mass of the most common isotope and the relative atomic mass or standard atomic weights can be very small, such that it does not affect most bulk calculations—but such an error can be critical when considering individual atoms. For elements with more than one common isotope the difference even to the most common atomic mass can be half a mass unit or more (e.g. chlorine). The atomic mass of an uncommon isotope can differ from the relative atomic mass or standard atomic weight by several mass units.

Yes atomic mass express for a single unit. It's unit is amu, like Atomic mass of Oxygen is 16 amu.

1 atomic mass unit = 1.66053892 × 10^-27 kilograms.

And 1 mole Oxygen = 16gm(not amu)

And 1 mole Oxygen = 6.022×10^23 number of Oxygen atoms.

So we can calculate the atomic mass by dividing 16/6.022×10^23 g which is same as that of 16 amu.