Question

PK TEACH ME CHEM

Answer 1

@ParthKohli

Answer 2

Yeah, thank you very much.

Answer 3

Let's start with stoichiometry.

Answer 4

YES!

Answer 5

All righty then.

Let's start with what a "mole" is. 1 mole is \(6.022 \times 10^{23}\) of anything. 1 mol of batmans is that many batmans.

Answer 6

mol is short for mole(s).

Answer 7

That's a lot of batmans

Answer 8

Yeah, IKR?

Moles have a pretty nice application in chemistry. Have you ever been through the periodic table?

Answer 9

Yup

Answer 10

Do you see how every element has its own atomic mass?

Answer 11

Yup

Answer 12

That atomic mass is expressed in atomic mass units, or amu, or simply u.

For now, we'll not go into the proper definitions, but you can think that 1 atomic mass unit is the mass of a hydrogen atom.

Answer 13

Well, I guess we should first see what other terms mean before we really move on to moles.

Answer 14

I know atomic number is the amount of protons in the nucleus of an atom.

Answer 15

Right. Very right.

Now, it's defined that if two elements have the same number of protons, then they'll be the same element.

But we also have neutrons in the nucleus! What if their number varies?

For example, hydrogen (which always will have atomic number 1) can have different numbers of neutrons: 0, 1 and 2.

Answer 16

all of these are hydrogen by definition, but they have different masses because they have a different number of subatomic particles.

Answer 17

So there are situations where you have to specifically tell the reader about the number of neutrons and the number of protons, you can write it in this way:\[\large X_{\large \rm atomic~number}^{\rm mass~ number}\]

Answer 18

Sorry, should be the other way.\[\large ^{\rm mass ~number}_{\rm atomic ~number}X\]

Answer 19

Where \(X\) is the symbol of the element.

The mass number is the sum of the number of protons and the number of neutrons.

Answer 20

Got ya

Answer 21

The mass number *does* tell you something about the mass of this, doesn't it?

Answer 22

So if we have something like that