Atomic models….and many dead white dudes
The concept of the atom – a smaller part that makes up everything – seems so self-obvious to those of us “in the know” that sometimes it can be difficult to remember that atoms are not something students regularly think about or contemplate. Nevertheless, we must teach about atoms and, even more than that, the smaller parts that make up atoms. For the State of Texas Standards (TEKS), we need to teach two interweaving ideas about atoms. First, that
8.5A describe the structure of atoms, including the masses, electrical charges, and locations, of protons and neutrons in the nucleus and electrons in the electron cloud
and then also that, since we cannot see atoms, we (scientists) need to use models to represent those tiny particles and their smaller parts.
8.3B use models to represent aspects of the natural world such as an atom, a molecule, space, or a geologic feature
The Middle School Next Generation Science Standards do not go into quite as much detail about atoms at the middle school level, where students only need to
MS PS1-1 Develop models to describe the atomic composition of simple molecules and extended structures.
But in the High School Next Generation Science Standards students need to be able to use the basic structure of atoms in various applications, although the basic subatomic structure itself never appears in the standards explicitly.
So that means we need to teach about atoms! [NOTE: I readily acknowledge that over 50% of what I teach in middle school science is either slightly incorrect or vastly oversimplified, but I hope I, and other middle school teachers, are just building a foundation for later enrichment and elaboration and not causing eternal damage]
I like to start off the atomic structure lesson by giving each table group a closed/stapled paper bag that contains some item.
I ask the students to work as a team to determine what is in the bag without opening the bag. The students usually enjoy this and then we go table by table, revealing their guesses, and then opening the bags.
After all the bags are opened (and put away neatly for the next class) I ask the students to discuss with their partners what they did to determine what was in the bag. Students usually include techniques such as shaking, poking, squishing, etc. Sometimes students smell the bag. Whatever they do, I bring back the discussion to how we can use other tools to determine the properties (there’s that word again!) of things that we cannot observe directly.
For many, many, many years, scientists have been using tools to observe and attempt to describe what everything is made of. We now say that everything is made of smaller parts called atoms. Most students have heard the term “atom” at some point in their lives but, given their adolescent brains and educational level, most don’t really have much of an idea what an “atom” is. I refer students to their note taking guide and ask each student to, independently, write or draw what they think when they think of “atoms”
Then we talk about what scientists currently think an atoms “looks” like using the Bohr model:
There is some debate about pre-teaching vocabulary versus exploration learning, but I think for something as abstract as an atoms you need to at least introduce some of the words ahead of time. So we draw an atom together and discuss the major part:
- Nucleus: the center of the atom (like the nucleus in a cell for those students who have had some biology); contains most of the “stuff” (mass) in the atom
- Proton: one of the particles in the center nucleus; relatively large; has a positive charge
- Neutron: one of the particles in the center nucleus; relatively large (about the same mass as proton); has no charge or is neutral
- Electron: very tiny particle that orbits around the nucleus in the region called the electron cloud; has a negative charge
Now that we have a basic idea of an atom, or at least have seen some new words related to atoms, I send the students off on a web quest to explore how scientists came to “uncover” this atomic structure. Most of the scientists, sadly, were old white men, but that is why we need to learn science now, so we can get more women and diversity out making important discoveries!
Here is a picture of the timeline that they fill out. This is on the inside of the notes page:
I let students select their level of reading/comprehension difficulty as “Mild,” “Medium,” or “Spicy” and then provide the appropriate links. [NOTE: Always have a backup plan if a link is bad or technology fails! I usually have a class set of printed readings or a basic slide show just in case]
|Mild (Just the Basics)||Medium (I’m feeling curious)||Spicy! (I want to be an expert!)|
|Basic History of the Atomic Model |
Atomic Theory Info Book
James Chadwick (scroll down to “Scientific Contributions)
Modern atomic theory
| Very detailed atomic model timeline |
History of the Atom(with descriptions of the different experiments used)
Sassy story of the development of the atomic model
After students have completed the webquest, they return to the front of their notes page to summarize/synthesize their understanding of the atomic model:
Extension: If time allows, I like to let students construct and label their own model of the atom using items that they can find around the classroom, in their pencil bags, or in the supply closet. ALWAYS IMPOSE CONSTRAINTS. Constraints generate creativity. My constraints are usually that the model must (1) show all four major parts of the atom (nucleus, proton, electron, neutron) (2) be able to hang on a wall (for storage later!) (3) be 3D (not flat) and (4) use only items in a certain space (5) contain useful, informative labels. It is fun to see what the kiddos come up with (and provides another good thing to decorate the walls)
To summarize the lesson, we all come back together and watch my very favorite explanation of the atom ever.
Now we know and can make a model of the subatomic particles, their locations, and charges. (NOTE: Be sure you also introduce the term “subatomic.” Many times I forget to do that and then use the word later to blank stares. Yes, the word is on the notes page, but unless you draw specific attention to that term no attention will be given and no memory will be made).