Mole of lithium atoms, how many lithium atoms do I have? That means that I have 6.02214076 times 10 the to 23rd lithium atoms. If I say I've got a dozen of eggs, how many eggs do I have? Well, if I have a dozen of eggs, that means I have 12 eggs. Now, what does that mean? Well, think about the word dozen. Used by the German chemist Wilhelm Ostwald at theĮnd of the 19th century, and he came up with the word because of its relation to molecule. Actually, it is both of those things, but, in a chemistry context, a mole is just saying you Now, what is a mole? It is not a little mark on your cheek. That it's very useful to familiarize yourself with in chemistry, and that's the idea of a mole.

Many significant digits, we will usually approximate it as 6.022 times 10 to the 23rd power. And, in most contexts,īecause you're not normally dealing with data with this There a name for this number, and there is indeed a name, and it is called Avogadro's number, named in honor of the earlyġ9th century Italian chemist, Amedeo Avogadro. Whatever its average atomic mass is in terms of unified atomic mass units, if you have that number of the atom, you will have a mass of that This number of lithium atoms, that sample is going to And, this number of atoms is 6.02214076 times 10 to the 23rd power. Number of atoms of lithium such that if I have that number, so times certain, certain number of atoms, then I will actuallyĮnd up with 6.94 grams, grams of lithium. We know its average atomic mass is 6.94, 6.94 unified atomic mass units Well, the chemistryĬommunity has come up with a useful tool. Masses at an atomic scale to the masses, masses of samples that you see in an actual chemistry lab, or in, I guess you could You're more likely toĭeal with several grams of an actual substance. You're very unlikely to justīe dealing with one atom, or just a few atoms, or That we might actually see in a chemistry lab. But, what we're gonna do in this video is connect it to the masses

Mass at an atomic level, or at a molecular level. Idea of average atomic mass, which we began to realizeĬould be a very useful way of thinking about a In a previous video, we introduced ourselves to the I hope this story/example helps out as a starting point for what can be a very difficult concept depending on how it is approached. Then I would go into the more specific and accurate details given by Just Keith to explain the concept thoroughly.

Now, for Chemistry when dealing with atoms, compounds or particles of elements, the 'convenient number' is the mole, which makes the use of the atomic mass numbers on the Periodic table manageable and much easier to use both in theoretical calculations and practical experimentation with chemicals. The last item, the salt, it would not be feasible to count out grains or even to determine the grain size being consistent, but would be more like the problems encountered for the much smaller atom/compound/molecule. I would just like to add maybe an even more basic explanation that I would employ to start with: when going to the grocery store to shop for you and your family, you would not pick up eggs individually anymore, or say 27 mL of milk or a specific amount of grains of salt (say 5000 grains), you would get say a donzen eggs, a litre/gallon of milk and specific mass/weight in gram/ounce of salt depending upon which unit of measure you use, this being more convenient and manageable number(s) when shopping.

I agree completely with Just Keith's answer of the over complication of this video along with his great detail on the background and mathematics of the mole and atomic mass unit.

Periodic table is molar mass or amu