Introduction to Ionic Bonding
Lesson 6 of 12
Objective: SWBAT predict the number and types of bonds formed between elements based on their number of outermost electrons and position on periodic table.
This lesson is aligned with 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" and aligned with PS1.A: The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.
In this lesson my students are introduced to ionic bonding. Prior to this lesson my students have been introduced to the concept of gaining and losing electrons to become an ion. In this activity students build on this knowledge using a Gizmo (ExploreLearning) that has them walk through a series of steps that shows electrons being removed by one atom and gain by another.
In this lesson students use the computer simulation to engage in the Science and Engineering Practice (SEP): Developing and using models. Students are able to see the process of ionic bonding by using the simulation and modeling the process of moving electrons from one atom to another.
To start class students will pick-up a copy of the ExploreLearning activity for the day and be instructed to take out the previous day's assignment so it can be checked it for credit. Most assignments that are checked in are worth 10-20 points; I made this assignment 10 points due the amount of time they were given in class to complete this.
In order to use this activity it will require a subscription. I am not certain of the cost, but the benefit of using a Gizmo as a resource for kids to model the NGSS SEP might be something worth looking into. If you choose to subscribe to ExploreLearning the website provides answer keys and lesson plans that suggest how to use their activities in a variety of classroom settings.
While I am walking around the room students are instructed to be doing three things in this order: Checking their homework for accuracy, answering the Prior Knowledge Questions on the worksheet that was picked up and logging into the computer (one computer per two students).
I like to do this activity in groups of two because the discussion that is generated during the exploration helps in the learning process.
After checking in the homework, I ask students if they have any questions about yesterday’s assignment. If there are no questions, we discuss the Prior Knowledge Questions.
The Prior Knowledge Questions are a bit pedestrian, but they do get students to recall that elements benefit from gaining and losing electrons. They ask students to comment on how a group of kids can achieve an equal number of markers during an art project by giving or receiving markers. This foreshadows ionic bonding by achieving a valence by gaining and losing electrons and act a good transition into the Gizmo.
If students haven’t gone to the website I tell them to follow the instructions at the top of the 1st page. Once at the website I model how the Gizmo works on the projector and let them know they need to read and answer each question before moving on to the next question.
As students are working, I walk around to make sure they are following the direction and give reminders that they need to assume all the shell beneath the valence shell are full of electrons.
After about 15 minutes most students are either on Activity B or getting close to starting it, so I stop the class and check for understanding by going over the first two sections. I do this to emphasize that all elements want 8 electrons and that they can achieve an octet by getting electrons from more than one atom. This information will help them in Activity B.
For the remainder of the period I walk around helping students work through Activity B and assess where they are struggling. During Activity B they should be building an understanding of how multiple elements, either metals or nonmetal depending on charge difference, can provide or take electrons. For example, Al can give one of its electrons to 3 separate Cl atoms to form AlCl3.
I like the ExploreLearning because it does an excellent job of walking students step-by-step through the process of creating ions and having them bond (student work example). In addition to being intuitively easy to use, computer models provide students with an engaging opportunity to visualize something that is microscopic.
As an alternative to this activity the PhET website offers a free Build an Atom activity that could be used to illustrate the formation of ions; however, it does not have a ionic bonding application.
Another website that can be used, but a little more advanced than the ExploreLearning, is The Concordia.org Molecular Workbench. This site walks the user through both types of bonding and has them write their answers directly on the website chalkboard. This site also has a lot of other Java applications that can be used for a variety of science concepts.
As they are finishing Activity B I let them know they need to answer the 5 Assessment questions (posted under the Gizmo) on a separate sheet of paper and turn it in by the end of the period (student work). These questions show me if students understand what type of ion (positive or negative) will form when gaining or losing electrons, what interaction occurs between a metal and nonmetal (metal losing, nonmetal gaining), the physical process (modeling) of transferring elections to form an ion and how to write an ionic compound. I find this to be a very concise formative assessment that is easier to grade than the entire ExploreLearning handout, allowing me to provide quicker feedback similar to an exit slip.