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The Bohr Model - atoms lesson 3

By Kim Fleming

Standards Match:

Objectives:

·        Learn the names, charges, and relative sizes of the fundamental particles that constitute an atom

·        Draw the Bohr model representing the arrangement of these particles in an atom

·        Realize that each atom is identified by some symbol in the periodic table

Time:40 minutes

Materials:

bulletOverhead of an ant, a pro wrestler, and a Buddha
bulletOverhead of the Bohr model for H, He, Li
bulletScience Journals

Review: There are 3 main parts – subatomic particles (like a submarine is inside the water – subatomic is inside the atom)

      1. Protons – Pro + (like a pro football player – pushing forward) RED IN PIC
      2. Electrons – negative – (think of all the negative advertising in elections) BLACK IN PIC
      3. Neutrons – neutral – (I’m not going one way or the other – I’m staying out of your fight) NOT IN THE PICTURES BELOW
      4. Each neutral element has a specific and unique (no other one like it) number of protons and electrons

Lesson

  1. The Bohr Model

·        Just like we already know, but now we are going to add in the Neutron

H hydrogen is the only atom with no neutron.  It only contains 1 proton and 1 electron

 

 
He Helium contains 2 electrons and two protons - and two neutrons (shown in red)
Li Lithium contains 3 electrons and 3 protons, but 4 neutrons

·        When we draw this model – we need to remember that these particles are in motion – with the electrons orbiting the nucleus (the part in the middle) just like the moon orbits earth, or planets orbiting the sun

·        The proton and electron have opposite charges

·        BUT!!! They are not the same size – that is: they don’t have the same mass

o       Electron  
very small and very strong like the ant (it takes about 1800 electrons to equal 1 proton)

o       Proton
very big (1836 ants = 1 pro-wrestler) – but exactly as strong as the electron

o       Neutron
just a bit bigger than the proton (pro-wrestler) – our peaceful and neutral Buddha neutron

 

·        With an overhead of a circle, and cut outs of the Buddha, the wrestlers, and the ant, build the Bohr atomic model

  1. Questions: (have students write their answers on white boards to make sure everyone is getting the concepts so far before moving on)
bulletThe element zinc (Zn) has an atomic number of 30.  How many protons does an atom of zinc contain?__________________
bulletA neutral atom of zinc contains how many electrons?__________________
bulletUsing the periodic table, determine the number of electrons in a neutral atom of copper (Cu).__________________
bulletThe neutral atom of He contains how many protons? ______ Electrons?______
bulletOf the primary fundamental particles in an atom:

1.      Which is the lightest in weight? ___________________

2.      Which is the heaviest? ___________________

3.      Which is between the other two in weight? ___________________

bulletIn the Bohr model of a lithium atom shown. Which subatomic particle(s) is (are) represented by the circular orbits shown by the larger circles? ______________ Which particles(s) make(s) up the nucleus or center of the atom?_____________________________
bulletIf the negative charge of an electron is represented by -1, the charge on the proton would be (-1, +1, neutral) __________ and the charge on the neutron would be (-1, +1, neutral __________.
bulletNeutrons can be found in all atoms of all elements except the most common form of the simplest element.  Identify that element.
  1. What we have learned so far about atoms:
    bulletIt is the smallest piece of an element?
    bulletWhat three subatomic particles make up an atom?
    bulletThat a proton is positively charged.
    bulletThat an electron is negatively charged.
    bulletHow many protons an atom contains from the periodic table.
    bulletWhy is H the first element in the periodic table?

Journaling (review/summary)

bulletDraw a picture that will remind you about the Bohr model and the relative sizes of electrons, protons, and neutrons
bulletWrite in words what you learned today.  How would you explain it to a 3rd grader?
bulletAlways questions – what comes next? – What do you wonder about now?

Looking Ahead

We will be looking at the weight of atoms and what makes up that weight.

 

Personal Teaching Reflection: Look for specific things that might improve the lesson.  See if students seemed engaged.  Look for personal interests to tie problems to real life. 

bulletWhat worked?
bulletWhat didn’t work?
bulletWhat would improve this lesson?