Build an Atom PhET
Name: _____________________________________ Period: _______
1. Go to https://phet.colorado.edu/en/simulation/build-an-atom
2. Click on the play button on top of the simulation preview to start the
simulation.
3. Click on the picture on the far left that says atom below it.
4. Explore the Build an Atom simulation.
A. Drag the grey, blue and red balls into the atom model and notice where
they appear.
B. Expand the element, net charge and mass number boxes.
C. Under “Show” click all the boxes.
D. Drag different numbers of grey, blue and red balls into the atom and
notice what changes happen.
5. Using Build an Atom, play with the parts of atoms to find:
A. What part(s), or subatomic particles(s), go in the center of the atom,
called the nucleus?
___________________________________________________
B. What subatomic particle(s), go in the outer rings of the atom?
___________________________________________________
C. How many electrons can fit in the first outer ring (closest to the center),
called an orbital?
___________________________________________________
D. How many electrons can fit in the second orbital?
___________________________________________________
E. Which subatomic particle(s) influence the stability of the atom?
___________________________________________________
F.
Play around and write down three examples of atoms that have a
stable nucleus and include a drawing of this nucleus.
Number of
Draw
What element
particles in
your nucleus
is it?
your nucleus:
1.
Protons: __
Neutrons: __
2.
Protons: __
Neutrons: __
3.
Protons: __
Neutrons: __
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6. Everything around us is made up of different elements. Which particle (or particles) determines the name of the element
you build?
_____________________________________________________________
7. Test your idea by identifying the element for the 3 cases.
Example
Atom or Ion has
# of protons: 6
1
# of neutrons: 6
# of electrons: 6
# of protons: 7
2
# of neutrons: 6
# of electrons: 6
# of protons: 6
3
# of neutrons: 7
# of electrons: 7
What Element is it?
8. Play with the simulation until you discover what affects the charge of your atom or ion. What is a rule for making...
A. An atom neutral (one with 0 extra charge)?
___________________________________________________
B. A +ion (positive ion, one with extra positive charge)?
___________________________________________________
C. A - ion (negative ion, one with extra negative charge)?
___________________________________________________
9. Show a neutral atom, a positive ion, and a negative ion. (These examples should be consistent with the rules you
discovered.) All of your examples should also have a stable nucleus.
Number of
Draw Your
What is
Particles?
Atom or Ion
the Charge?
Neutral
Protons: __
Neutrons: __
Electrons: __
+ Ion
Protons: __
Neutrons: __
Electrons: __
- Ion
Protons: __
Neutrons: __
Electrons: __
10. Play until you discover what affects the mass of your atom or ion. Which particles don’t affect the mass?
______________________________________________________
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11. What is a rule for determining the mass?
______________________________________________________
12. Using all of your rules, figure out what changes for each of these actions to an atom or ion. You can test your ideas with
the simulation.
What
Action
How Does it Change?
Changes?
☐ Element
Add a
Proton
Action
☐ Charge
☐ Mass
What
Changes?
How Does it Change?
☐ Element
Remove a
Neutron
Action
Remove
an
Electron
Action
☐ Charge
☐ Mass
What
Changes?
How Does it Change?
☐ Element
☐ Charge
☐ Mass
What
Changes?
How Does it Change?
☐ Element
Add an
Electron
☐ Charge
☐ Mass
13. Design challenges:
A. Design a positive ion with a charge of +2. Include a drawing:
Number of protons __
Number of neutrons__
Number of electrons__
i. What is the element of your ion? ______________
ii. What is the mass of your ion? ________________
iii. Is the nucleus of your ion stable or unstable (circle)?
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B.
Design a neutral stable ion with a mass of 9. Include a drawing:
Number of protons __
Number of neutrons__
Number of electrons__
i. What is the element of your ion? ______________
ii. What is the charge of your ion? ________________
iii. Is the nucleus of your ion stable or unstable (circle)?
14. At the bottom of the screen click the symbol button (middle) to learn more
about symbols for atoms.
15. Explore the symbol tab in the simulation until you learn what each part of
the symbol signifies.
A. What does the 3 tell you in the picture above?
_____________________
B. What does the 2 tell you in the picture above?
_____________________
C. What does the “He” tell you in the picture above?
__________________
D. What does the +1 tell you in the picture above?
____________________
16. Write the symbol for the ion you drew in #13A
17. Write the symbol for the atom you drew in #13B
18. At the bottom of the screen click the game button (right) to practice what
you have learned so far.
19. Start with the element game on the left.
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20. Play the game until you get at least 4/5 stars. Record your score ____/10
21. Next, play the mass and charge game (second from the left).
22. Play the game until you get at least 4/5 stars. Record your score ____/10
23. Next, play the symbol game (third from the left).
24. Play the game until you get at least 4/5 stars. Record your score ____/10
25. Lastly, play the “?” game.
26. Play the game until you get at least 4/5 stars. Record your score ____/10
CHECK FOR UNDERSTANDING: answer the following questions to demonstrate
what you have learned. You may use the worksheet and the simulation.
1. Which subatomic particle(s) are the same in the following two atoms
demonstrated by their corresponding symbols? (Hint figure out the
number of protons, neutrons and electrons for each atom using the
symbols and compare)
37
-1
35
Cl
P
19
-1
17
P
Cl
Protons
Neutrons
Electrons
2. What two subatomic particles have to be balanced in order to produce
a net charge of 0 for an atom?
3. Draw a representation of an atom with 12 protons, 12 neutrons and
10 electrons.
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