Science is so amazing and useful. I love teaching a subject that is easily applicable and practical in everyday life. I sometimes wonder why specific topics are selected for the science curriculum given that those topics, while important, will rarely be encountered outside the academic realm. This topic is one of those – valence electrons.
This lesson specifically addresses Texas Science Standards
8.5B identify that protons determine an element’s identity and valence electrons determine its chemical properties, including reactivity
The Next Generation Science Standards, on the other hand, specifically exclude this topic in the explanation for MS-PS1:
MS-PS 1.1 Develop models to describe the atomic composition of simple molecules and extended structures. ….. [Assessment Boundary: Assessment does not include valence electrons and bonding energy….]
Given that my classroom is in Texas, we teach valence electrons in 8th grade, but we make it fun (or so I hope). Introducing…
Before this lesson, students need to be familiar with the basic structure of an atom (protons, electrons, and neutrons) as well as the Bohr model of atomic structure. Once those concepts are in place, then it is time for a little drama. [NOTE: I usually borrow some hats from the theater teacher and put on a whole production, so dress it up or down as you see fit]
Part 1: Teacher Prep. Before class I gather samples of aluminum (just use foil), silicon (we have some pure in the chemistry closet but you can use sand, silicon dioxide, in a pinch), and magnesium (this one you probably need to order in advance).
At the beginning of class, select four willing volunteers from your classroom to play the starring roles of Miss Oxygen, Mr. Magnesium, Mr. Aluminum, and Mr. Silicon [NOTE: Being gender inclusive and LBGTQ friendly is important these days, so I either give a preface about using the Bachelorette as a model and assuming heteronormativity or I let the students choose the gender relationship. Depends on your classroom climate]
Part 2: Meet Miss Oxygen. Explain that Miss Oxygen is a contestant on The Bachelorette and she’s looking for her perfect match. I give Ms. Oxygen a little script and have Ms. Oxygen tell the class about herself. The narration is accompanied by my drawing (and the students drawing in their notes page) a profile picture for Ms. Oxygen.
“Hello. My name is Olivia Oxygen and I am a nonmetal in Group 6A. At room temperature I appear as an amazing transparent gas but don’t let my lack of visibility fool you, I am explosive in the presence of the right energy! My mass number is 16 and my atomic number is 8, so I have 8 protons, 8 neutrons, and 8 electrons. As you can see from my profile, I have 6 valence electrons. I’m looking for someone to complete my outer shell.“
Part 3: Introducing the Suitors. Each element introduces himself with the script provided, similar to Miss Oxygen. [NOTE: I make my drawings a little messy on purpose to encourage the kiddos to hurry along and not be little perfectionists!]
Hi Miss Oxygen. I’m Sam Silicon. I’m not your average mental or nonmetal. In fact, I’m a metalloid! Without me, the modern technological economy would be impossible! I have 14 protons, 14 neutrons and 14 electrons. I’m well balanced that way! I’ve got 4 valence electrons ready and waiting for you.
Greetings Olivia. I’m Albert Aluminum [If you’ve got theater kids in class this one is fun to do in a British accent]. I’m a metal and very malleable. I have 14 neutrons, just like Mr. Silicon over there, but I have a lucky 13 protons and 13 electrons. I’m excited to get to know you and see if you are interested in my three valence electrons.
Hello Miss Oxygen. I’m Mark Magnesium. I’m also a metal, like Mr. Aluminum, but I’m way over on the left of the Periodic Table in Group 2. I’ve got 12 protons, 12 neutrons, and 12 electrons. I’d like to invite you over to my side of the table and see how you like my 2 valence electrons.
Part 4: The Candlelight Dinner. Now it’s time to take each of the eligible elements on a date with Miss Oxygen. Do this under a vent hood or somewhere with good ventilation! [I accidentally set off the fire alarm once doing this and we evacuated the school – oops!]. Set up a candle and light the candle.
Explain to the students that Miss Oxygen like to be early, so she’s already present at the “restaurant” where the candlelight dinner takes place (i.e. she is in the air….but only about 21%, not all ambient air is oxygen).
One at a time, take each sample of the element from the student actor. Use a piece of sand paper or other rough surface to give the sample “a little polish and spiff up” before the date (this ensures the candle will interact with the element, not an oxidized coating). Use tongs to hold the element into the flame and see if there is “good chemistry” with Miss Oxygen.
Mr. Aluminum (the aluminum sample) should just get a little black with soot from the candle flame. Mr. Silicon (the silicon or sand sample) might melt a little but mostly nothing happens. Mr. Magnesium, on the other hand, burns bright white – OMG ! That’s a hot date! (some students get the pun, some don’t)
Part 5: Discussion and Reflection. Why did Mr. Magnesium have good chemistry with Miss Oxygen? Because atoms (at least at the very basic level in which we are teaching) want to fill their outer shells with valence electrons. In periods 2, and 3 on the periodic table, atoms with 8 valence electrons are “happy atoms,” nice and full with their electron shells. In high school chemistry students learn more about covalent and ionic bonding but, for now in middle school, we just say that atoms like to meet together to get enough valence electrons to make 8 total. Elements in the first period, Hydrogen and Helium, just need 2 valence electrons to be “happy” because the first orbital level in atoms only has two “seats” (you hopefully explained this in the lesson on atomic structure).
To help students remember the number of valence electrons needed, I made a little jingle for “The Bachelorette: Elemental Edition”
If you want to get a date, just call the number 2, 8, 8!(Two electrons in shell level 1, 8 in shell level 2, and 8 in shell level 3 – that’s enough for middle school level understanding)
I then have the students answer the reflection questions on their notes page and we discuss as a class:
Another good extension question is which OTHER elements might be good suitors for Miss Oxygen? [anything with 2 valence electrons….or 2 atoms with 1 valence electron each, hence H2O] And then from there we go on combining atoms to make molecules! But that is fun for another day. Do a knowledge check and tell the kiddos good job! (be sure to return any props you borrowed to keep your local theater teacher happy)