All posts by David Swart

High school science teacher

Ions, Ionic Compounds, and Formulas

Our work today introduced students to the concept of ions: atoms with positive or negative charge.  Up to now, students have considered atoms to be neutral, because we have discussed atoms as having equal numbers of protons (positive charge) and electrons (negative charge).  While atoms can certainly remain neutral, many atoms exist in nature as ions.  Atoms gain or lose electrons in predictable ways to form ions, and ions partner up in predictable ways to form ionic compounds.

A neutral atom has equal numbers of protons and electrons.  When a neutral atom loses one or more electrons, the atom will have fewer electrons than protons, and thus will have a positive charge.  We call a positively charged atom a cation (an ion with a positive charge).  Cations are often metals.  When a neutral atom gains one or more electrons, the atom will have more electrons than protons, and thus will have a negative charge.  We call a negatively charged atom an anion (an ion with a negative charge).  Anions are often non-metals.

Just like the positive end of one magnet is attracted to the negative end of another magnet, cations and anions attract.  When a cation bonds with an anion, an ionic compound forms.  The bond between the ions is called an ionic bond.  Ionic compounds can be simple: one cation with a +1 charge bond will bond with one anion with a -1 charge.  Similarly, one cation with a +2 charge will bond with one anion with a -2 charge.  If a cation with a +2 charge bonds with an anion with a -1 charge, the +2 cation will actually bond with two -1 anions, creating an ionic compound with three ions: one cation and two anions.  This is because anions and cations bond together following the Rule of Zero Charge: the positive and negative charges sum to zero.  Ions commonly exist in charges of +1, +2, +3, -3, -2, -1.

The charge of an ion for a given element is predictable.  It’s actually built into the structure of the periodic table.  Focusing on the main group elements:

  • Group 1A elements readily give up one electron to form +1 cations.
  • Group 2A elements give up two electrons to form +2 cations.
  • Group 3A elements give up three electrons to form +3 cations.
  • Group 4A elements don’t often give up or take electrons and thus remain neutrally charged (no charge).
  • Group 5A elements take three electrons to form -3 anions.
  • Group 6A elements take two electrons to form -2 anions.
  • Group 7A elements greedily take one electron to form -1 anions.
  • Group 8A elements don’t give up or take electrons and remain neutrally charged (which is why they are called Noble Gases – they don’t interact with other elements).

We then practiced writing formulas of ionic compounds using our improved understanding of the periodic table.

For extra help, the video below will review ions:

For additional support writing ionic formulas, students are encouraged to watch the video below:

Flame Test Lab

To begin class, students received back their Chapter 3 quizzes.  We briefly reviewed the quizzes and then turned our attention to our first big lab of the year: The Flame Test Lab.  To prepare for the flame test lab tomorrow, we watched the video below:

Next, students received a copy of the Flame Test Lab and we read through the procedure and then answered the pre-lab questions.

Tuesday, October 15: Flame Test Lab

After completing the lab, students were assigned to complete analysis questions 1 and 2 as homework.

Wednesday, October 16: Notes from the white board (very short class period because of the PSAT) are below.  Students had the class period to complete the table and analysis questions during class.  Those who did not finish should complete the work as homework.



Students are encouraged to review the Lesson 17 PowerPoint.

Homework for this evening:

  • Read Lesson 17 in the textbook.  Login via and enter your Synergy username and password.
  • Work through the exercises at the end of Lesson 17.
  • Come to class tomorrow prepared to ask questions about anything from Lesson 17 you do not yet fully understand.


Monday, October 14, 2019 (HS-LS1-4): Mid-unit 1 quizzes are due at the beginning of class for full credit.  Late quizzes will receive a maximum score of 60%.

Having learned about DNA last week, it is time to focus on the process of cell division.  Mitosis, or somatic cell division, involves the division of one cell into two after all of the components of the original cell (including the DNA!) divide into two sets.  We began by watching a Crash Course video about mitosis:

After the video, students were assigned to read pages 46-51 of chapter 4 (Cellular Reproduction: Multiplication By Division) of Inside the Cell.   Students then answered the following questions in their lab notebooks:

  1. Explain the purpose of mitosis.
  2. Which cells undergo mitosis?
  3. Describe the phases of mitosis in detail (words and/or drawings).
  4. Explain what happens when cells divide uncontrollably.  List the known causes of uncontrolled cell division.

Tuesday, October 15, 2019: Class began with a brief discussion of questions 1 and 2 from yesterday’s reading assignment.  After the discussion, students had the remainder of the class period to complete the reading and questions, and then to work in teams to create a time-laps video of mitosis modeled with Play-Doh.

Wednesday, October 16, 2019: PSAT

Thursday, October 17, 2019: As we continue our study of mitosis, students will invest the next two days researching what happens when cells divide uncontrollably.  Students will use The Eukaryotic Cell Cycle and Cancer Interactive tool from HHMI BioInteractive to explore how errors in DNA copying during mitosis can lead to cancer.

Students may choose between the overview worksheet (beginner) and the in-depth worksheet (advanced).

Friday, October 18, 2019: Students have the short Friday class period to complete The Eukaryotic Cell Cycle and Cancer worksheet activity from yesterday.  Students who finish early should extend their understanding of cancer treatments by watching the Ted-Ed video below about biohacking cells to fight cancer.  After watching the video, students may earn up to +5 bonus for writing a summary of how scientists are creating CAR-T cells to upgrade the human immune system to fight cancer.

Need a break from the study of cancer?  Learn about the amazing process of regeneration in planaria!  After watching the video below, students may earn +5 bonus for writing a summary of the RNAi experiments (blocking the activity of beta-catenin and APC) in planaria.

Unit 1 Project

Unit 1 Project

Background: With the end of our first unit of chemistry in sight, consider all you have learned thus far.  Our initial review of matter (including mass, volume, and density) led to an introduction of the periodic table.  We learned about the history of atomic models, explored how atoms are constructed (protons, neutrons, and electrons) and how changing those particles impact an atom.  We learned that the elements are born in stars, with heavier elements forged in the explosive forces of supernovae, while unstable atoms experience decay over time.  We learned that neutrons decay into protons, protons decay into neutrons, and atoms can gain or lose electrons according to well-defined rules (main-group elements) and less-well-defined rules (transition metals).  We learned how to assemble ions into compounds, how to identify the metals in ionic compounds using the flame test, and how to write electron configurations of elements according to the number of electrons in subshells.

“The cosmos is within us.  We are made of star stuff.  We are a way for the universe to know itself.”

What does this quote mean to you?  Your assignment for this project is to unpack Carl Sagan’s famous quote, applying what you have learned during chemistry in unit 1 to your own effort to know yourself.

Deliverable: A well-written essay shared with Mr. Swart as a Google Doc.  Incorporate as many Unit 1 vocabulary words as possible (highlight in bold font if you want them to count toward your total!), in a manner that isn’t forced, to demonstrate mastery of the unit and a deep understanding of yourself.  I look forward to learning more about you!

Due Date: Friday, November 8, 2019

  • Chapter 1: What are your intensive and extensive properties? What makes you who you are and you don’t see changing over time (intensive properties)?  How have you changed over time, and what changes do you anticipate for yourself in the future (extensive properties)?
  • Chapter 2: Where does your name come from? What does your name mean to you?  What does your name mean to others?  What symbols best represent who you are and why?  Consider your reactivity: what gets you excited?
  • Chapter 3: Models of the atom have changed over time – just like people!  Think about how well your teacher and classmates know the real you.  How well do you know the real you?  What are your most important parts (your metaphorical protons, neutrons, and electrons).  Share insights about yourself that are not obvious to someone who doesn’t know you well and would like to know you better.  What are your needs (fusion)?  What are your gifts to the world (particles shared through decay – let’s make decay a good thing!)?  What are your hopes and dreams, and how will they positively impact others (fission)?
  • Chapter 4: Electrons are the way atoms interact with each other?  We can predict how an atom will interact with other atoms based on its electron structure.  What about you?  Are you that predictable?  What do you intend to accomplish this year, five years from now, ten years from now?  What do you see as your most likely path when you look to the future?  How about your path if you were an ion, able to clear out or add a few extra electrons and make life really interesting for yourself – if there were no constraints on your future, what would you want to accomplish?

Grading: Your essay will be evaluated as a unit exam, a category that comprises 25% of your semester grade.

Grading Rubric:

Vocab Words (from chapter 1-4 notes) 20 or more 15-19 10-14 Less than 10
Content Self-reflection from all 4 chapters thoroughly explored Self-reflection from 3 chapters thoroughly explored Self-reflection from 2-3 chapters moderately explored Self-reflection surface-level or more than two chapters missing

Formation of Elements

To begin class, students moved to their new seats and then attacked entry task question #2 with their new seat partners.





Next, students were asked to share out a response to the question: where do the elements come from?  After a brief discussion, we watched the video below:

Next, we worked through the PowerPoint to learn more about the concepts of fusion and fission, and then students used the remainder of class to work on the Lesson 16 Worksheet.  This is the final textbook lesson of Chapter 3.  On Tuesday, we will continue our exploration of nuclear reactions with a Gizmo activity in preparation for the Chapter 3 test on Thursday.

Class notes for October 8:


Week 6

Monday, October 7: Students will write up a lab report of last Friday’s strawberry DNA extraction lab report.  The lab report will include the following components:

  • Student name
  • Lab report title
  • Introduction (explain the purpose of the lab)
  • Procedure (numbered list of steps someone could follow to recreate the experiment you are reporting on)
  • Results (observations from the lab)
  • Conclusion (what was learned, three areas of improvement, and explanation of the “next” experiment)

Tuesday, October 8: Students repeated the strawberry DNA extraction experiment from last Friday, testing the experimental question “Which type of soap is better at extracting strawberry DNA?”  Students conducted the extraction twice, using extraction solution prepared with either Dawn dish soap (orange) or Suave shampoo (blue).  Students took pictures of their results to include in their revised lab report.

Notes from class today:

Wednesday, October 9: To begin class, students shared out the results from their lab yesterday.  We then made connections between procedure steps, extraction solution components, cell structure, and DNA precipitation.  Students had the remainder of the class period to update their lab reports and to bulk up the Introduction and Conclusion sections of the lab report by incorporating what was learned today.

Thursday, October 10: For our final day of class this week, students had the opportunity to complete their lab reports (due today) or begin the take-home quiz (due Monday).

Friday, October 11: No School / For homework over the long weekend, students will complete the mid-unit take-home quiz.