Moles of Protons

Question

What formula do you use to get the answer to this question...

How many moles of protons are there in one mole of Li2+?

Answer 1

Kello, Lain,

You want to know the number of protons in one mole of Li²⁺ ? Wow. Get a life.

Sorry - I couldn't help myself. I enjoy this type of question, but it makes me realize how what a nerd I am. But you'll enjoy the answer:

The term mole is just a nickname for a number: 6.02 x 10²³ . It I say I have one mole of something, it can refer to atoms, protons, marbles, days, paperclips, girlfriends, ants in my kitchen, . . ., well, you get the idea. It's like using the words dozen, peck, score, century, etc.

You might well question why anyone would want to pick a number like this and give it a name. Why not choose something more sensible, like simply 1 x 10²³ . Good question.

It had been experimentally determined that the number of atoms in 12 grams of carbon is 6.02 x 10²³

. It is also called Avogadro's Number, in honor of Avogadro's discovery that equal volumes of different gasses, under the same conditions of pressure and temperature, have the same number of atoms. It's a longer story, but the important magic is that this number also allows one to take the atomic weight of any element or compound and that number (e.g., The atomic weight of Li is 6.94 AMU (atomic mass units) can be restated as "the number of grams of that element or compound that will contain 6.02 x 10²³ atoms of that item. It is a useful conversion factor for scientists, since now they don't have to count out each atom one by one. The mass will tell them how many atoms they have. Great!

This brings us to your question. We know that we have one mole of Li²⁺ . The 2+ means that this atom has lot two electrons, which takes some convincing for Li [Li normally only loses 1 electron before becoming very protective of what is left].

So we have 6.02 x 10²³ atoms of Li in it's unfortunate state of undress. Looking at the Periodic Table, we see that the atomic number of lithium is 3. The atomic number is the same as the number of protons in an element. So the number of protons in one mole of Li is 3 * 6.02 x 10²³ protons. = 1.806 x 10²⁴ protons.

The 2+ means two electrons have left, but the protons stay the same, thus the resulting 2+ charge. It still has 3 protons, but only one electron now. 3p³⁺ +1e^- results in the positive 2 charge. The point here is that the protons don't change. If they did, it wouldn't be lithium anymore. The number of protons define what the element is.

So the number of protons in one mole of Li²⁺ is 1.806 x 10^{24 protons.}

Bob

Answer 2

Lain

Li has atomic number 3, so 3 protons in each atom of Li. Li 2+ is a lithium atom that has lost 2 electrons, so each Li 2+ ion still has 3 protons.

So obviously 1 mile of Li 2+ will have 3 moles of protons

Mike