Chemistry
LAB
Name: ______________________________
Period: ____ Date: ___________________
LAB: The MASSIVE Atom
Purpose: To demonstrate that the mass of the atom is concentrated in its nucleus.
Materials:
marbles = Protons
cotton balls = electron cloud
push pins = electrons
clay/play dough = neutrons
laboratory balance
The Nucleus
The nucleus (plural, nuclei) is a positively charged region at the center of the atom. It consists of two types of
subatomic particles packed tightly together. The particles are protons, which have a positive electric charge,
and neutrons, which are neutral in electric charge. Outside of the nucleus, an atom is mostly empty space, with
orbiting negative particles called electrons whizzing through it. The Figure above shows these parts of the
atom.
Size and Mass of the Nucleus
The nucleus of the atom is extremely small. Its radius is only about 1/100,000 of the total radius of the atom. If
an atom were the size of a football stadium, the nucleus would be about the size of a pea!
Electrons have virtually no mass, but protons and neutrons have a lot of mass for their size. As a result, the
nucleus has virtually all the mass of an atom. Given its great mass and tiny size, the nucleus is very dense. If
an object the size of a penny had the same density as the nucleus of an atom, its mass would be greater than
30 million tons!
Holding It All Together
Particles with opposite electric charges attract each other. This explains why negative electrons orbit the
positive nucleus. Particles with the same electric charge repel each other. This means that the
positive protons in the nucleus push apart from one another. So why doesn’t the nucleus fly apart? An even
stronger force—called the strong nuclear force—holds protons and neutrons together in the nucleus.
PROCEDURE:
Part I: Building a Neutral Atom
1) You and your lab partner will be given a card with the name of an element and it’s mass number on one
side and an isotope on the other. USE THE SIDE MARKED NEUTRAL ATOM. Record the name of your atom
on your data-sheet.
2) Use the marbles to represent the protons. Count out the correct number of protons needed
for your atom and record it in Chart #1.
3) Take the Play-Dough ® and make it into little spheres, each one about the size of a marble. The
Play-Dough ® spheres represent neutrons. Make as many neutrons as you need and record the
number in Chart #1.
4) Place the marbles from step #2 and the Play-Dough® spheres from step #3
into the plastic weigh dish. Raise your hand to get your teacher’s approval
before going on to step 5.
5) Squish together your marbles (protons) and Play-Dough spheres (neutrons)
to make a nucleus. Place your nucleus in the plastic weigh dish and then place the weigh dish
on the balance. Record the mass in Data Table # 1.
6) Use the colored pencils to draw the nucleus in the box marked Diagram 1. You should include a key.
7) Find the cotton balls and place them around the nucleus to create a “cloud”. Stick the
“cloud” to your nucleus.
8) Find the push-pins. Gather enough push-pins to represent the number of
electrons you need and record this number in Chart #1
9) Stick the pins in the electron Cloud. Now raise your hand and get your teacher’s approval before
moving on to the next step.
10) Add the cloud and the electrons to your drawing in Diagram 1. Label each part of your drawing.
11) Put your atom on the balance and record the mass as Mass B in the data table. You can now calculate the
mass of the electrons by subtracting Mass A from Mass B and record this value as mass C in your data
table. Show your calculation below the data table.
12) Now take apart your atom and return all of the parts to their original containers.
PROCEDURE:
Part II: Building an Isotope
1) Now flip your card over to the side that says “Isotope”. Follow the above procedure marking down all the
data in Part II. (Make sure to get approval at all the same places!!)
2) When you are finished, disassemble your isotope and return all materials to their original containers.
LAB: The MASSIVE Atom (Data-Sheet)
Part 1 – Neutral Atom Name: _________________________________________
Chart #1:
Subatomic Particle Number
Location
Diagram 1 – Neutral atom
KEY:
= ______________
= ______________
= ______________
Data Table 1 – Neutral Atom
WORK
Mass A – mass of Nucleus (marbles + clay)
Mass B – Mass of Atom (marbles + clay + cotton + pins)
Mass C –CALCULATE
Mass of Electrons and Electron Cloud
(Mass B – Mass A)
ANSWER:
Part 2 – Isotope Name: _________________________________________
Chart #2:
Subatomic Particle Number
Location
Diagram 2– Isotope
KEY:
= ______________
= ______________
= ______________
Data Table 2 – Isotope
WORK
Mass A – mass of Nucleus (marbles + clay)
Mass B – Mass of Atom (marbles + clay + cotton + pins)
Mass C –CALCULATE
Mass of Electrons and Electron Cloud
(Mass B – Mass A)
ANSWER:
LAB: The MASSIVE Atom
Post-Lab Questions (show all work for full credit)
1) What was the mass of the nucleus of your neutral atom (Mass A)? __________________
2) What was the mass of your ENTIRE neutral atom (Mass B)? __________________
3) What was the mass of your electrons and electron cloud of your neutral atom (Mass C)? ______________
4) Calculate the percent of your atom that was nucleus by doing the following calculation (SHOW WORK)
TAPE DATA-SHEET HERE AS A FLAP – tape one side only!
Mass A (nucleus) x 100
Mass B (entire atom)
Show Work
Answer:
5) Calculate the percent of your atom that was electrons by doing the following calculation
(SHOW WORK)
Mass C (electrons) x 100
Mass B (entire atom)
Show Work
Answer:
6) What subatomic particles are in the nucleus of an atom?
____________________________ and _____________________________
7) What subatomic particle is NOT in the nucleus? Where is it located?
____________________________ _____________________________
8) What part of the atom has the most mass? ___________________________________
9) What part of the atom has the least mass? ___________________________________
10) What subatomic particle did you alter when making the isotope form of your atom?_________________
11) How did the alteration in #10 affect the atom? (HINT: What changed as a result of the alteration?
OR…what is the difference between your neutral atom and your isotope?)
_______________________________________________________________________________________
_______________________________________________________________________________________
LAB: The MASSIVE Atom
Purpose: To demonstrate that the mass of the atom is concentrated in its nucleus.
Pre-Lab Questions:
1) Using your TEXTBOOK define mass number.
__________________________________________________________________________________________
________________________________________________________________________________________
__________________________________________________________________________________________
2) What does the mass number tell you about an atom?
__________________________________________________________________________________________
________________________________________________________________________________________
3) Using your TEXTBOOK define atomic number.
__________________________________________________________________________________________
________________________________________________________________________________________
__________________________________________________________________________________________
4) What does the atomic number tell you about an atom?
__________________________________________________________________________________________
________________________________________________________________________________________
5) Where is nearly all of an atom’s mass located?______________________________________________
6) What part of the atom takes up most of the space? ___________________________________________
7) ) Complete the chart
Particle
Electron
Proton
Neutron
Symbol
Location
Relative
Charge
Relative
Mass