2.Atoms, Ions, and Molecules

For each chapter we cover, I prepare a page with practice problems, study guides, useful links, etc. as relevant. The practice problems are marked either:

Fundamental: start on these early in content coverage

Challenge: do these later to prove to yourself you're close to mastering a topic.

I will also update the page on occasion as we work through the material. Check back often!

Naming Compounds:

Anchor

Fill in the following table. “Type of compound” will be a sub-class/note-to-self of ionic compound that helps you determine how to name the compound (this isn't exactly asking for an official term, just a place to put your notes.) Examples include inorganic acid, transition metal-containing, etc.

Reveal Answers

Isotopes, Abundance, and Average Atomic Weights

Naturally occurring chlorine is 75.78% Cl, which has an atomic mass of 34.969 amu, and 24.2% Cl, which has an atomic mass of 36.966 amu. Calculate the average atomic mass (that is, atomic weight) of chlorine. How can you check if your answer is correct?

Reveal Answer

What might be some other ways you’re asked about calculating atomic weights? If all you had was a periodic table, what other info would you need to report the percent abundances of naturally occurring isotopes?

Reveal Answer

Polyatomic Ions

Like learning a new language, learning Chemistry sometimes requires some memorization. For now, polyatomic ions is one of those times. When we learn Lewis structures, you will discover how looking at bonding and electron distributions help us systematically determine charge of a polyatomic ion.

However, like a language, the names and charges of polyatomic ions do have some internal logic and patterns that can help you as you learn them, even without knowing the structure of the ion. To the left is a chart of common ions similar to the one in your textbook and below is a list of questions to consider and exercises to complete that will help you learn these.

Some questions to answer for yourself:

What do you notice about what -ide indicates compared to -ate or -ite in the chart above of common ions?

Some things to note:

All the ions above are anions except ammonium. Ammonium is the only

Oxoanions:

A large portion of the polyatomic anions are oxoanions. Try making a chart of these with an organization scheme as shown below. You can organize all of the anions which contain a particular central element in a row by degree of oxygenation. The oxoanions of chlorine are shown as an example. Once you’ve done this with all the oxoanions you want to look at (carbon-containing, nitrogen-containing, sulfur-containing, and phosphorus-containing would be my minimum suggestion), answer some of the following questions for yourself:

What do the suffixes -ate and -ite indicate? What about prefixes hypo- and per-?
What do you notice about the charge on the oxoanions of a given element?
What are the exceptions/places where the naming conventions seem to deviate from a perfect system? (Note that different students might answer this question differently. Polyatomic naming systems are historical, which means they may not always be perfectly consistent. You may understand the inconsistencies somewhat differently than another person, but pointing them out for yourself is an important step in learning the names.)
How has what you’ve learned from answering these questions helped you to understand the naming for some of the more exotic oxoanions, like the ones based on transition metals