Reading Notes for Chapter 2

These are Dr. Bodwin's reading notes for Chapter 2 of "Chemistry 2e" from OpenStax. I am using a local .pdf copy that was downloaded in May 2020.

Chapter Summary:

What kind of stuff is stuff made of? This chapter has a LOT of material that we will be using as our "language" of chemistry throughout the course. There are quite a few rules and lists in this chapter that people often think about as just something to memorize, but it's all information that you will probably be using regularly enough that it becomes part of your natural memory.
Bad Chemistry Joke of the Chapter: Never trust an atom, they make up everything.

Dalton's Atomic Theory:

This is an excellent example of what a theory is. Using the best available information at the time, Dalton compiled an explanation that was consistent with that information. It's pretty amazing. As technology has advanced and the information we are able to observe about matter has become more detailed, there are a number of part of Dalton's Atomic Theory that aren't quite correct so they have been updated and clarified by subsequent atomic theories. That's how scientific knowledge is developed, tested, refined, and grown!
The laws of definite proportion/constant proportion/multiple proportions are observations that distinguish between "compounds" and "mixtures" as discussed in Chapter 1. Compounds are substances that have a very specific number of atoms (elements) combined in a constant ratio. If you change the ratio, you change the compound.

Atomic Theory and Structure:

There are lots of animations and videos that look at atomic theory online, search "atomic theory animation" and you'll find a ton that are aimed at different audiences. One that I found is:
https://www.learner.org/series/chemistry-challenges-and-solutions/atoms-and-light-exploring-atomic-and-electronic-structure/models-of-the-atom/
To define different atoms, we need to keep track of the subatomic particles and what they tell us. Protons define the identity of the element, neutrons (with protons) define the mass and isotope of the atom, electrons define the charge of the atom or ion.
Atomic number, mass number, and charge are ways to keep track of the subatomic particles.

Chemical Symbols and the Periodic Table:

Chemical symbols including atomic number, mass number, and charge tell you everything you need to know about the subatomic particle makeup of an atom.
The Periodic Table is arranged by atomic number... we'll get into a bunch of different things the Periodic Table can tell you as we work through the next few chapters.
NOTE - I do not expect anyone to sit down and memorize the Periodic Table just for the sake of memorizing the Periodic Table. If you want to do that, go ahead. I do expect that you will remember a number of the common elements because you will be using them very often or they are in very common usage outside of a chemistry classroom context. When I use an uncommon element in a homework or quiz question, I will often give its atomic number to help you find it on the Periodic Table, so as long as you know what atomic numbers are, you should be able to find the element.
Learning the group names of the Periodic Table can be quite useful. Figure 2.27.

Chemical Formulas:

Back to the "compounds" from Chapter 1 and the laws of proportion from earlier in this chapter, a chemical formula describes the whole number ratio of different elements in a compound.Practice reading, writing, and interpreting these because we will be using them constantly throughout the course.
Ionic vs Covalent - Here's an important distinction to get figured out. Ionic interactions occur between charged species; covalent interactions involve sharing electrons in a "bond".
Ionic interactions tend to occur between elements that are farther apart on the Periodic Table (like sodium and chlorine); covalent interactions tend to occur between elements that are closer to each other on the Periodic Table (like carbon and oxygen).
You can have BOTH ionic AND covalent interactions within the same compound (like sodium carbonate).
Species that only experience covalent interactions are called molecules.
NOTE - I do expect you to memorize the polyatomic ions in Table 2.5. It looks like a long list, BUT:

If you look at the systematic nomenclature rules (right after the table), you'll see that a bunch of the oxoanions in the list are redundant (if you know the naming rules). For example, if you "memorize" that sulfate is SO₄^-2, then (by using the naming rules) you also know that sulfite is SO₃^-2.
My hope is that, at least for some of the more common polyatomic ions, you will use them often enough that you just remember them rather than specifically trying to "memorize" them. For example, I will probably use nitrate in half the examples and homework problems in this course. After looking it up 20 or 30 times, you'll just remember that nitrate is NO₃^-1.
There are a couple others that you might see, but if you have all those in the table, you'll be able to handle them. A few specific "extra" polyatomic ions: bromate & iodate (same as chlorate), phosphite, thiocyanate, and thiosulfate.

Chemistry nomenclature seems like it has a lot of rules, but it's something that really does get easier with just a reasonable amount of practice. The biggest thing to remember is that for neutral ionic compounds, the total positive charge must equal the total negative charge

Memorizing polyatomic ions and practicing chemical formulas and nomenclature are a couple cases where flashcards work extremely well for many students. Literally, flashcards with one thing written on one side and the "answer" written on the other. Make yourself a stack (or 2 or 3...) and go through them whenever you have a few minutes to spare.

Return to ChemBits General Chemistry Index.

All information on this page is produced by Jeffrey Bodwin, Copper Sun Creations, or curated from the attributed source.

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.