Atomic mass
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Search complete. 25 mentions across 4 episodes found for "Atomic mass".
Oct 15, 2026
Michael RussellHOST
We've got three isotopes, seventy-two, seventy-three, and seventy-four.
Michael RussellHOST
And the question here is what would be the best atomic mass, which is the average atomic mass, of this element? Now again, you can solve this a couple different ways.
Michael RussellHOST
See what you can do with this problem.
Michael RussellHOST
We'll talk about both ways, uh, to solve it here in a little bit.
6 MINS LATER
Michael RussellHOST
Now, some of you will dig that explanation and some of you won't, and that's totally fine.
Michael RussellHOST
The math way to do this problem is to multiply the mass numbers by the decimal percent and add them all together.
Michael RussellHOST
So if you're a math person, go seventy-two times point five four five, plus seventy-three times point one five six, plus seventy-four times point two nine nine, and that's another way to get the best value here for the average atomic mass.
Michael RussellHOST
But boy, either way you do it, seventy-two point eight is, is the, is the answer here.
Kevin O'KeefeHOST
So as our understanding multiplied, this is important to also know, which we alluded to before.
Kevin O'KeefeHOST
With our elements, you have atomic mass, and then you have isotopes.
Kevin O'KeefeHOST
Well, with the atomic mass, every atom contains protons and neutrons in its nucleus, as I mentioned, and these particles account for almost all of its mass or how much matter it contains.
Kevin O'KeefeHOST
If you add the number of protons and neutrons together, you get this mass number.
Kevin O'KeefeHOST
So for example, a carbon atom, a common carbon atom has six protons and six neutrons, giving it a mass number of 12.
Kevin O'KeefeHOST
But on the periodic table, you'll notice that carbon's atomic mass is about 12.01. You'll see decimal numbers.
Kevin O'KeefeHOST
And why will you see them? Well, it's because the number on the periodic table represents an average of the masses of the different naturally occurring versions of carbon in this example.
Kevin O'KeefeHOST
Why is all this important? Well, it can help scientists understand how heavy different atoms are, and therefore, they can calculate how much of each element is needed to make different substances.
Michael RussellHOST
And he proposed that there would be some scale to measure them with.
Michael RussellHOST
And this scale is now based around what's called an atomic mass unit, an AMU.
Michael RussellHOST
And you can see down there at the bottom that an atomic mass unit is a very small amount of mass, 1.66 times 10 to the minus 24 grams.
Michael RussellHOST
Now, a pound of something in our macroscopic world, a pound is about 454 grams.
Michael RussellHOST
This is many, many orders of magnitude smaller, so it's very small.
18 MINS LATER
Michael RussellHOST
Now, another important part about an atom is what's called the mass number.
Michael RussellHOST
And mass number gets the symbol A.
Michael RussellHOST
And usually the mass value, by the way, is in atomic mass units, the AMUs we talked about earlier.
Michael RussellHOST
The molar mass was a term I used earlier, and that's the grams that are f- found in the element in a mole, and this is actually a pretty easy thing to kind of figure out, which is really, really cool.
Michael RussellHOST
And [clears throat] the cool thing is that based on the language I showed you either, the molar mass of any substance is numerically equivalent to its atomic mass in AMUs.
Michael RussellHOST
So all those average masses we were talking about, like the antimony is never gonna be one twenty-one point seven six if you have exactly one atom, ha ha, that number also represents the grams of antimony in a mole, and that's what's really cool.
Michael RussellHOST
So here's the punchline.
Michael RussellHOST
Those numbers on the periodic table, the atomic masses, have two meanings.
Michael RussellHOST
If you have a single carbon-twelve atom, mass is gonna be twelve AMU.
Michael RussellHOST
But if you have a mole of pure carbon-twelve, that's gonna have a molar mass of twelve grams.
Michael RussellHOST
My mind gets blown every time I talk about it, I won't lie.