This lesson summarizes NGSS HS-PS1-1, "use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms".
The goal of the lesson is to provide my students with a chance to review everything they have learned throughout the unit: Atomic structure, location of subatomic particles, charge of subatomic particles, Rutherford’s Gold Foil experiment, J.J. Thompson’s model and Coulombic Attraction based on electron distance and atomic size. This is aligned with the NGSS Disciplinary Core Idea (DCI) PS1.A (Structure and Properties of Matter): “each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons”.
In this lesson students explore the structure of the atom using the NGSS Science Practice 2, Developing and using models by visiting various stations and review previously learned content about atomic models. The stations review has students recall evidence that subatomic particles are present within an atom and sets the stage for the unit test. It also prepares them for the next unit on periodic trends and bonding, HS-PS1-2.
The Cross Cutting Concept (CCC) that is illustrated in this lesson is Patterns. Patterns are illustrated as students continue to reinforce the concept that as elements change so do the number of protons and electrons, along with Coulombic attraction.
I like to provide my students with the occasional opportunity (once a unit) to earn a little extra credit to offset what can be a difficult first unit. So, I give them the opportunity to “stump the teacher” and write a couple of test questions in their Journal. The goal is to have them write higher-order questions that synthesize knowledge and have them move beyond simply recall of content. I instruct them that the 2 best questions will be used on the test as extra credit and the two I pick will get additional extra credit (1 or 2 pts on the test). This motivates them to think about what they have learned and helps them think about new information. A couple of examples of questions that would qualify as higher order are:
(1) When electrons get further away from the nucleus, what happens as the get closer to other atoms?
(2) If opposites attract and like repel, why don’t the electrons get pushed away from the nucleus by other electrons?
An additional purpose for asking them to write questions is that questioning is one of the NGSS practices and this activity will help develop questioning skills for when we move beyond guided inquiry into open inquiry.
After a couple of minutes I ask them to turn in their journals so I can grade them during the review and pick the best two questions for extra credit. As they drop off their journals I have them pick-up a unit 1 review answers sheet.that they will use to record their answers as they move around the room to different review "stations". The review sheet mirrors the stations minus the pictures found at each station. This structured answer sheet helps organizes students information so they can use it later to study. I also encourage students to take pictures if they need to visualize some of the images that are at each station. Many of my students take advantage of this, mostly because they get to use their phones in class.
The unit 1 stations review is set up in 14 stations around the room that contain 2-4 questions per station. I try to break up the questions so that one station does not take longer than the next. This prevents students from standing around not doing anything. I have found if they are standing around too long, they start switch stations without being cued which can lead to chaos.
After students pick up their answer sheets I show them how the station rotation will work. I keep it simple so that it makes an easy pattern around the room. I then arrange the students in groups of two and set them up at various stations.
Prior to this activity my students have done stations, but only seven which were set up at each of the lab tables in the picture. For this activity I kept those stations the same way I always have, 1-7 going clockwise around the room starting at the far lab table on the left side of the room ending at 7 in the middle. I then have the other seven stations going around the room clockwise with 7 starting by the windows and 14 end at the cabinets. This was very simple for the students and provides no confusion where to go. I also put the questions in plain sight taped to the table tops, that way they do not have to look for them. I suggest that stations be set-up in the simplest way so that students can apply little thought as where they need to go next.
I instruct them not to move until I say next. I set a timer for 1:30 and 2:00 minutes and start after the 1st station because they tend to start right when they get to their station.
It's common during the review that students ask for the answers if they don’t know it, but I resist the urge to give them answers and tell them to work with their partner. I do this because we will go over at the end in a group format where every group has to share an answer. The whole review should take no longer than 25 minutes just so they don't lose interest.
As an evaluation I have each group come up to the document cam (ELMO) and discuss one of their answers. I find the best way to assigning questions to answer is the station they started at will be the station they will explain to the class.
If there are any questions or disputes, I have the students correcting one another; this acts as a brief introduction to the NGSS practice of engaging in argumentation from evidence. As a class, the correct answer always is worked out and this gets everyone involved in the learning process. Due to a time constraint, if students engage in argumentation too long (30 sec) I will interject and provide the answer. The goal is to get all students the right answer so that they will be ready for the test, not debate right and wrong answers.
Stations 2 (questions 4, 5 & 6) and 10 (question 28) seem to provide the most trouble for students. They typically forget that the like charges repel and that an atom is mostly empty space with a very small positively charged nucleus. They also struggle with distinguishing the force of attraction between the inner and valence electrons and the nucleus. Eventually the students will come to the right answer with me guiding them in the right direction, but again time can be an issue with getting students too engaged in debating answers. Drawing a Bohr's model on the board will usually illustrate that an atom is mostly empty space. Than I will use arrows to illustrate force of attraction between inner and outer electrons.
If there is not enough time to complete the answer sheet, I have in the past started the next class finishing it; it acts as a great pre-test review and helps get my students motivated to take the test. At the end of the review, I put my answer key on the ELMO to make sure everyone has the right answers.