Atoms

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Objective

Students will be able to identify the 3 major subatomic particles and understand how electrons fill energy levels within the atom.

Big Idea

It's not a "Bohr" if you know how electrons fill energy levels.

Warm-up

5 minutes

Begin with the Warm-Up question, “If an apple were an atom, what would be the core?”  Pause for 20-30 seconds before accepting any responses to the question.  Pausing is an effective way to encourage students to ponder a question before reaching an answer too quickly.  Pausing also allows students who process information more slowly a chance to process the question and develop their own answer before they start hearing other students answers to the question.

Listen for students’ understanding of atoms in their responses.  Look for students to identify the nucleus as the core. Students’ ability to make this connection suggests that they have some prior knowledge about atoms having a center called a nucleus. 

Explain that today’s learning targets are that students will learn the parts of an atom and how to diagram an atom.  

Introduce New Material

20 minutes

Begin the lesson with a presentation of key vocabulary for the lesson: atom, elements, compounds, ion, nucleus, proton, neutron, electron, isotope, pure, stable, atomic number, atomic mass, orbital, electron cloud, covalent bond, ionic bond.  Instruct students to add the term, isotope to their Vocabulary Map as is the practice for new terms that contain Latin or Greek root words, prefixes or suffixes.

Present key points about atoms using an LCD projector.  Instruct students to take notes using guided notes that you have provided or a note-taking format that you have taught.  Walk around the room as you teach to observe student activity.  It’s important to ensure that students are writing down the key points of the discussion. Openly acknowledge those students who are utilizing note-taking best practices like using highlighters or adding to the notes by writing additional information in the margins of the notes.  This is a great way to reinforce desirable behaviors.

Note: I provide highlighters on the tables for students’ use and I use a digital pad to model the practice of highlighting key points as I teach.  I tell students that “If I am writing additional information or highlighting, you should be writing additional notes or highlighting, as well”. 

Display a Bohr model slide show using a LCD projector.  Select three volunteer readers to act as the three parts of the atom and participate in the reading of the lines from the slide show.  Explain that each reader must read his/her part with feeling as the lines appear on the slide.  Ask the rest of the class to follow along as the three students read the lines. 

This slide show is useful because the information about atoms reads like a play, in which the three particles of an atom are personified.  The animation and dialogue in the slide show helps students gain a better understanding of the relationship between particles of an atom and how they behave in relation to one another. 

After completion of the notes and the slide show, conduct a brief check for understanding using a set of questions that will allow students to test themselves to see how much they recall from the information they just heard(without the use of notes).  To increase student engagement, divide the class into 3-4 groups that will compete against one another to answer the questions correctly.  Competition is a great motivator for many students and the prize for winning can simply be bragging rights or a piece of candy for each member of the team that answers the most questions correctly.

Guided Practice

10 minutes

Remind students that the learning target for the day includes being able to draw atomic models.  Display a table of 6 elements. Using the carbon atom as the example, model the steps of the process to identify the number of protons, neutrons and electrons for the carbon atom.  Also model how to identify the number of orbitals needed for the number of electrons found in the carbon atom:

1. Think aloud as you identify the atomic mass and atomic number directly from the table. Show students the relationship between the atomic number and number of protons, the atomic mass and number of protons and neutrons, and number electrons and number protons in a neutral atom.# protons = atomic number
# electrons = # protons in a neutral atom
# protons + # neutrons = atomic mass   

2. Use your formulas to calculate:

  • # ProtonsThink aloud: “I know I have 6 protons because Carbon has an atomic number of 6 and the atomic number is equal to the number of protons.
  • # Electrons: Think aloud: “I know I have 6 electrons because the  number of electrons is equal to the number of protons.
  • # NeutronsThink aloud: I can rearrange the equation above to find the number of neutrons. The atomic mass minus the number of protons is equal to the number of neutrons. So, 12(atomic mass) -6 (protons)  =6 neutrons.

3. Think aloud to identify where the electrons reside.  Note that only the protons and neutrons reside in the nucleus.  Refer back the Bohr Model slide show and point out that the electrons were circling the nucleus in rings called orbitals.

4. Display the maximum number of electrons each of the 1st three orbitals can hold. Think aloud to determine how many orbitals are needed to hold the number of electrons for carbon.  Explain the term, maximum and use several synonyms for the meaning of the term so that students will clearly understand its meaning. The term maximum can be a difficult term for some students to grasp.  Ask, “How many electrons can the orbital hold up to?” to help scaffold the concept until its meaning is understood. Make sure students understand that you must fill one level before going on to draw another.

  • Think aloud, “I know I have 6 electrons because the atomic number is equal to the number of protons.  Therefore, I have 6 electrons that I need to place in orbitals.  I can place a maximum of 2 electrons in the first orbital and 4 in the 2nd orbital, which can hold up to 8 electrons.  I don’t need 8 electrons in the 2nd orbital so I am done because 2+4 = 6 and all the electrons have been placed in orbitals.

5. Draw the atomic model for carbon with the protons, neutrons and electrons and orbitals noted. Emphasize the maximum number of electrons that can reside in each of the 1st three orbitals. However, also emphasize that only two orbitals are needed for carbon’s six electrons. It is not necessary to teach beyond the 1st three orbitals since we won’t deal with elements that have electrons beyond the first three orbitals.

 

Independent Practice

20 minutes

After modeling the process for atomic models, display the atomic model isntructions on the LCD projector. Distribute copies of the atomic model instruction, paper and markers. 

Walk students through the instructions and model how to fold the paper:

  1. Fold the paper in half (hotdog).
  2. Fold in half again.
  3. Fold in half once more. 
  4. The paper should now have 8 equal squares. 

Use the top two squares to recreate the table from the Atomic Model Instruction sheet. Make sure that students copy and complete the table before attempting to draw the atomic models.  Failure to complete the table first will create confusion about how many electrons are associated with each atom.

Instruct students to label each of the remaining 6 squares with the names of the elements from the table.  If you choose, distribute copies of paper with pre-printed labels.  This might be especially helpful with students who have difficulty following verbal directions.

Explain what information should be calculated and placed in the table: # protons, # neutrons, # electrons, and # electrons in orbitals 1-3.

Explain that students are expected to draw the atomic model in the 6 squares for each of the elements in the table, using the numbers they've calculated.

Walk around to ensure that students are completing the assignment as prescribed in the instructions.  Look for the common error of creating more orbitals than are needed, especially for the hydrogen element. Students will tend to draw two orbitals for hydrogen, even though only one orbital is needed. When this happens, use it as a teachable moment to explain that the models only need as many orbitals as are needed for the number of electrons for that atom in theelectron configuration.

Watch for students who may be struggling as they work independently to complete the assignment.  Encourage students to write out the calculations if needed to help them determine the number of particles in each element.  The first student work atomic model  evidences that students were able to complete the assignment correctly.  The second atomic model  student sample evidences the creation of  visually appealing work using markers and colored pencils.  The third atomic model student sample evidences a higher level understanding, as evidenced by how the student configured the electrons in energy shells.

Close

5 minutes

Instruct students to complete a Ticket Out the Door:

Write P, E and/or N on the line if the statement describes protons, neutrons or electrons.

1.___ The atomic number is equal to this particle of the atom.

2.___ This particle has no charge.

3.___ These make up the mass of an atom.

4.___ This particle has a negative charge.

5.___ These are found in the nucleus of an atom.

Use the student responses as a formative assessment to determine if further instruction on atoms is warranted.