Build an Atom — Assignment
Instructions
For this activity, you will be using the Build an Atom simulation on the PhET website. The web address
for this simulation is given at the beginning of the lab handout under Web Link. You can also click here
to take you to the simulation. During this activity, you are going to find the location of subatomic
particles in an atom. You will also discover which particles affect the name, charge, and mass of an atom.
After starting the simulation, you will be shown three options “Atom”, “Symbol”, and “Game”. Choose
the “Atom” option.
1. After you are on the Atom tab of the simulation. Under “Model” choose “Orbits”. See figure 6 for
where to locate the particles and properties of the created atoms. Drag and drop protons, neutrons,
and electrons onto the atom in the center of the screen.
Figure 1: Screenshot of PhET Build an Atom Simulation Atom Tab
While varying the number of particles, observe how the element, charge, and mass number change.
Explore the simulation, and then answer the following questions.
Questions
1. When you add the following particles, where do they go (the nucleus or in orbits)?
a. Protons
b. Neutrons
c. Electrons
2. What particle(s) determine the name of the element you build?
Build an Atom
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3. What is the name of the following atoms?
a. An atom with 3 protons and 4 neutrons: _____________
b. An atom with 2 protons and 4 neutrons: _____________
c. An atom with 4 protons and 4 neutrons: _____________
4. Think about which particles affected the charge of the atom or ion, and fill in the blanks below to
show your results:
a. Neutral atoms have the same number of protons and electrons.
b. Positive ions have ________________________________ protons than electrons.
c. Negative ions have _______________________________ protons than electrons.
5. Develop a relationship (in the form of a single sentence or equation) that can predict the charge based
on the number and types of particles.
6. Think about which particles affected the mass number of the atom or ion. What is a rule for
determining the mass number of an atom or ion?
Practice applying your understanding by playing 1st and 2nd levels on the game screen.
Build an Atom
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Activity 2: Symbol Screen
For this activity, you will continue using the Build an Atom simulation on the PhET website. During this
activity, you are going to practice using the isotope notation and investigate how the number of each
particle affects the notation.
1. Choose the “Symbol” tab at the bottom of the simulation see figure 7. Explore the simulation by
dragging and dropping protons, neutrons, and electrons onto the atom in the center of the screen and
observing which particles affect each component of the symbol in the isotope notation.
Figure 2: Screenshot of PhET Build an Atom Simulation Symbol Tab
2. After determining how the particles change the element symbol, atomic number, charge, and mass
number of the isotope notation, you will record your data in table 2. For each element property, you
will write the particle(s) used to determine that property and how the value of each property is
determined in table 2. Note: Refer to figure 4 in the prelab for a reminder of the generic isotope
notation. Table 1: Description of Components of Isotope Notation
Generic
isotope
notation letter
Element
Property
Particle(s) How the value is determined
X Chemical
symbol
C Charge
Z Atomic
number
A Mass
number
Build an Atom
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Practice applying your understanding by playing the 3rd and 4th game levels. Play until you can get all the
questions correct on the 4th level.
Questions
1. Create a definition (using a complete sentence) for each of these items based on your data in table 2.
a. Element Symbol
b. Charge
c. Atomic Number
d. Mass Number
2. In addition to the isotope notation, we can represent atoms by name and mass number. For example,
the name of the 𝐶1+6 12 ion is carbon-12, and the name of the 𝐵𝑒4
9 atom is beryllium-9. What is the
isotope name for the following?
a. 𝐿𝑖1+3 6
b. 𝐹9 18
c. 𝐵5 11
d. 𝑂2− 6 12
3. For each pair of atoms listed below. Write whether the atoms are 1) Isotopes, 2) Same Atom, Not
Isotopes of Each Other, OR 3) Different Elements?
a. Atom 1: 𝐶6 12 and Atom 2: 𝐶6
b. Atom 1: carbon-12 and Atom 2: 𝐶6 12
c. Atom 1: argon-40 and Atom 2: argon-41
d. Atom 1: 𝐵5 11 and Atom 2: boron-10
e. Atom 1: an atom with 13 protons & 13 neutrons and Atom 2: an atom with 14 protons & 13
neutrons
Build an Atom
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4. As a reminder, here is the figure that contains the first 10 elements, their symbols, and the number of
protons in their nuclei. Use this figure and the information given for each isotope in table 3 to
complete table 3.
Figure 3: Electron Configurations for the First 10 Elements and List of Names and Chemical Symbols
Table 2: Some Isotopes and Their Properties and Components
Name Isotope
Notation
Atomic
number
Mass
Number
Number of
neutrons
Number of
Electrons Charge
hydrogen-2 𝐻1 2 1 2 1 1 0
𝐻1 3
lithium-4 𝐿𝑖1+3 4 2
carbon-12 6
carbon-13 6
carbon-14 6
carbon-12 7
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1. When you add the following particles where do they go (the nucleus or in orbits)?,
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2. What particle(s) determine the name of the element you build?,
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3. What is the name of the following atoms?,
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4. Fill in the blanks to show results about charge.,
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5. Develop a relationship that can predict charge based on particles.,
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6. What is a rule for determining the mass number of an atom or ion?,
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Activity 2 Question 1: Create definitions for Element Symbol, Charge, Atomic Number, Mass Number.,
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