Reading Notes for Chapter 2

These are Dr. Bodwin's reading notes for Chapter 2 of "Introduction to Chemistry". I am using a local .pdf copy that was downloaded in August 2020.

Chapter Summary:

In order to understand the macroscopic world, it helps to understand the microscopic world! Matter is made of atoms.

Chemical Elements:

The basic chemical building blocks of all matter are called elements.
Each element is represented by a name and a 1-letter or 2-letter symbol. The "Note" on page 85 of your textbook given some examples of element names and symbols that might seem odd if we're thinking about them in English, but make more sense if we look at their roots in other languages.

Atomic Theory & Atomic Structure:

What makes you "you"? That's a tough question with a LOT of answers. For chemical elements, it's a little easier. If your have lump of some pure element, you can break it down into smaller and smaller pieces, and those pieces will still be that element, but at some point you will break it down into a small enough piece that it can't be broken apart any more without ceasing to be that element... it will just be a bunch of random tiny pieces. These "tiniest pieces of an element" are atoms.
The "Plum Pudding" model of atomic structure is now often called the "Chocolate Chip Cookie" model of atomic structure, because people today don't really understand what "plum pudding" is. Why didn't they call it the "Chocolate Chip Cookie" model back when it was discovered? Because chocolate chip cookies weren't invented until the 1930s...
Atomic Theory Overview (https://www.youtube.com/watch?v=xazQRcSCRaY)
Atoms are composed of a small nucleus (that contains almost all of the mass of the atom in the form of protons & neutrons) surrounded by a cloud of electrons.
Protons = positively charged subatomic particle, located in the nucleus
Neutrons = uncharged subatomic particle, located in the nucleus
Electrons = negatively charged subatomic particle, located outside the nucleus

Keeping Track of Subatomic Particles:

So elements are made of atoms, and atoms are made of subatomic particles. If the number of subatomic particles change, something about the element changes. We need to be able to keep track of these things...
Atomic Number = # of protons. The identity of an element is defined by the number of protons in its nucleus, so the atomic number defines what element we're looking at.
Mass Number = (# of protons) + (# of neutrons). Because the protons and neutrons make up almost all of the mass of an atom, their sum is called the mass number. Atoms with the same number of protons, but different numbers of neutrons (different mass numbers) are called isotopes.
Charge = (# of protons) - (# of electrons). Because electrons exist in a cloud outside the nucleus, they can often be lost or gained without really affecting the nucleus. Atoms with unequal numbers of protons and electrons have a charge and are called ions.

NOTE: If you want to memorize a formula for charge, go for it, but you can always just think about the charges of the individual subatomic particles to figure out the charge on an ion. If I have an ion with 26 protons (each with a +1 charge, so +26 total in the nucleus) and 23 electrons (each with a -1 charge, so -23 total outside the nucleus), then the total charge on the ion must be +3!
NOTE2: Your textbook doesn't really go into charge until the next chapter, but I include it here because this is where we're talking about numbers that describe subatomic particles. We'll dig deeper into charge in Chapter 3...

Where do electrons live?:

Most of the chemistry we observe takes place in the electron cloud, so it's very important to be able to keep track of those electrons.
The address system we use is called quantum numbers. Quantum numbers are like the state, city, street address, and apartment number where you live.
Quantum numbers and electron orbitals (https://www.youtube.com/watch?v=Aoi4j8es4gQ)
Quantum numbers are important, but they contain a little more information that we usually need for this course. Electron configurations are a shorthand for quantum numbers. Here's a little more basic example of writing electron configurations:
Writing electron configurations (https://www.youtube.com/watch?v=iFN9agJVea4)
There's also a helpful version of the Periodic Table in your textbook, figure 2.10, that can help with electron configurations.

Your Best Friend - The Periodic Table:

The Periodic Table is packed full of information, and we'll be using it constantly throughout this course. I would strongly suggest printing out a copy (or a couple copies...) or saving a dedicated copy so you can jot down some notes on it or color code it. Here's a plain Periodic Table that you canuse for that:
(http://www.drbodwin.com/teaching/pt1lnd.pdf)

Do not memorize the Periodic Table. By that I mean, don't sit down with the P.T. and intentionally try to memorize it just for the sake of memorizing the P.T. It might help you win a trivia contest, but it's not a useful activity for this class. You will always have access to a P.T. when you need it for doing homework or quizzes or exams. As with many things, you will very likely begin to memorize the parts or the P.T. that you use repeatedly, and that is great, but don't spend your time and mental energy just memorizing the P.T.

NOTE: As I have already done here, I will likely refer the the Periodic Table as "the P.T."

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