Structure of atom

Introduction: (Initial Observation)

Many inventions and new technologies developed in the past few decades rely on a good understanding of the atom and its subatomic particles. Production of electricity, function of electronic components, television, X-Ray, light and atomic energy are just a few of the technologies that are based on the properties of atoms.

Making a model is a good way of learning about atom and other chemical structures. In this project you will make a model of an atom of your choice.

Make a model to display the number and the position of electrons, protons and neutrons in your atom.

Examples provided are for making a model of Argon atom; however, you can follow the same procedures for any other atom as well.

Information Gathering:

Find out about the structure of atom and subatomic particles. Read books, magazines or ask professionals who might know in order to learn about one specific atom of your choice and then try to make a mode of that. Keep track of where you got your information from.

Information about atom may be found in both chemistry books and physics books. If you are planning to search the Internet for the information, search for Bohr atom, Bohr’s atom or Bohr Model.

Following are samples of information you may find:

Atoms are composed of three types of massive subatomic particles which govern their external properties:

• electrons, which have a negative charge and are the least massive of the three;
• protons, which have a positive charge and are about 1836 times more massive than electrons; and
• neutrons, which have no charge and are about 1838 times more massive than electrons.
• Protons and neutrons are both nucleons and make up the dense, massive atomic nucleus. The electrons form the much larger electron cloud surrounding the nucleus.

Atoms differ in the number of each of the subatomic particles they contain. The number of protons in an atom (called the atomic number) determines the element of the atom. Within a single element, the number of neutrons may also vary, determining the isotope of that element. Atoms are electrically neutral if they have an equal number of protons and electrons. Electrons that are furthest from the nucleus may be transferred to other nearby atoms or even shared between atoms. Atoms which have either a deficit or a surplus of electrons are called ions.

Argon Atom:

By searching the Internet, encyclopedia, and periodic table of elements you will see that Argon has 22 neutrons and 18 protons in its nucleus. It also has 18 electrons orbiting the nucleus in three different energy levels. First energy level has 2 electrons, second energy level has 8 electrons and the remaining 8 electrons are in the third energy level.

Although each energy level or shell is not an orbit, in our simplified model we make one orbit for each energy level.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to build a model of Argon* atom.

* Replace Argon with the actual atom that you are going to make a model of.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Defining variables is not required for making a display model of atom.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

No hypothesis is required for making a model of atom.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment/ Activity:

Introduction: In this experiment you will gather information about one specific atom and its subatomic particles. You will then use such information to make a 3D model of the atom. In this sample activity we will try to make a model or Argon atom.

Materials:

• About 100 Small Styrofoam balls. You will need one ball for each electron, one ball for each proton and one ball for each neutron.
• Three different color latex paint and brush for painting the balls
• Wood glue or white glue
• Chenille stem (available in the arts/ craft departments of large stores)
• Thread for hanging the model
• Pins (ball pins/ ball head pins)

Procedure:

• Use different resources to find out the number of neutrons, protons and electrons of your specific atom. (The number of electrons and protons are the same).
• For each neutron in your model, get a Styrofoam ball, paint them (any color of your choice) and let them dry.
• For each proton in your model, get a Styrofoam ball, Paint them (any color of your choice, other than the color you used for neutron) and let them dry. Use a small black marker to right a + sign on each proton. This will remind you that protons have positive electrical charge.
• For each electron in your model, get a Styrofoam ball, Paint them (any color of your choice, other than the color you used for neutron and proton) and let them dry.
• Use wood glue to connect the neutrons to each other. This collection of neutrons will be at the center of your model.
• Use wood glue to connect the protons right over the neutrons. Protons and neutrons together will form the nucleus of the atom and will stay in the center of your model. You may optionally mix neutrons and protons so the viewer will see both at the same time.

 

• Find out how the electrons will be distributed among different shells. Each shell has a limited capacity that is 2n2. In this formula n is the shell number. In this way the shell 1 will hold 2 electrons. Shell 2 will hold 8 electrons. Shell 3 will hold 18 electrons. Use the information you have gathered to decide how the electrons are distributed among different shells. At this time you are just calculating and deciding how many shells you will need and how many electrons will reside in each shell. You will later make orbits to represent shells or energy levels.
• Make circles using Chenille stem wire or any other wire that is available to you. For example if you need 3 orbits, make 3 circles. The circles will have different diameters. In this way the orbit 1 will be the closest to the nucleus. You may use tape to connect the wires; however, a better practice is to connect the wires using the Styrofoam balls you use as electrons. To do this apply some wood glue to the end of the wire and then insert it in the Styrofoam ball. In this way electrons will join the pieces of wires. See details in step 10.

 

• Place the nucleus on the center of a table and place the orbit/shell circles or rings around it. Inspect the distances and make necessary adjustments. Make sure there is at least 2 inches space between different circles.

 

 

 

 

 

• Insert the orbit wires from an open end into the Styrofoam electrons. Position the electrons equidistance from each other. Now join the ends and complete the circles. You may need to twist the ends to each other or use some tape.
• When the orbits are ready, use sewing tread to hang them. Please note that all orbits should not be on the same plane like the position they had on the table.

 

Tips and tricks:

 

When you make a half deep cut on a Styrofoam ball, you can use that cut to mount the ball anywhere on the orbit. You can also use that cut to connect pieces of chenille stem wire. The Chenille stem wire can easily slide into the grove and hold the ball in place.

 

 

 

Picture in the right shows Chenille wire rounded up and both ends are inserted in the cut, completing a circular orbit. Additional balls may be mounted on the wire later.

 

 

 

 

 

 

This close up picture shows how the Chenille wire slides into the cut or grove you create in the Styrofoam ball.

 

 

 

 

Protons and neutrons can be connected to each other using wood glue. Ball head pins will temporarily hold the pieces together while the glues dry.

 

 

 

In the construction of argon model, we used:

• 2 pieces of 12″ Chenille stem wire for orbit 1 (shell 1);
• 4 pieces of 8″ Chenille stem wire for orbit 2 (shell 2);
• 4 pieces of 12″ Chenille stem wire for orbit 3 (shell 3);

 

 

 

To assemble your final 3D model hang a 3 feet long thread somewhere. Then hang the largest circle to this string (close to the top). A knot can hold it in place. Continue with hanging smaller orbits in the same way and finally hang the nucleus in the center. You may need to use two pins at the top and bottom of the nucleus and tie the thread to the needles. Continue to make knots below the nucleus so the orbits will stay in shape. Diagram in the right shows some of the patterns you may use to connect the orbits and nucleus using sewing thread.

Materials and Equipment:

This is a sample list of materials:

• About 100 Small Styrofoam balls. You will need one ball for each electron, one ball for each proton and one ball for each neutron.
• Three different color latex paint and brush for painting the balls
• Wood glue or white glue
• Chenille stem (available in the arts/ craft departments of large stores)
• Thread for hanging the model
• Pins (ball pins/ ball head pins)

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

If you do any calculations for your project, write your calculations in this section of your report.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of References

http://www.ndt-ed.org/EducationResources/HighSchool/Electricity/atommodels.htm

http://www.mcwdn.org/chemist/atom.html

http://csep10.phys.utk.edu/astr162/lect/light/bohr.html

Atomic Orbitals : This is a more advanced discussion about distribution of electrons in an atom.

More about electrons in atoms

Electronic structure of atoms (Very advanced)

Question: I have found my element in the periodic table of elements and I know how many electrons it has. I need to know how these electrons are distributed among different shells or energy levels.

Answer: What you should know first is that the electrons in one shell or energy level are moving on specific paths known as orbital. We use symbols s, p, d and f to represent the shape of orbitals. For example 2p means p orbitals of shell 2. (Shell 2 has one s orbital and 3 s orbitals.) Each orbital will hold up to 2 electrons and electrons will fill up orbitals in a special order shown below.

The sequence of energy and filling is:

Example: Argon has 18 electrons. The first 2 electrons will enter 1s (1s means orbital s of shell number 1); Two more electrons will enter 2s; Each of the three p orbitals in shell 2 will get two electrons; 3s will get two electrons; Each of the three p orbitals in shell 3 will get two electrons. If you ignore the orbitals and just focus on shells, you will see that shells 1, 2 and 3 will get 1, 8 and 8 electrons.

The table below shows the distribution of electrons in different shells regardless of the shape of orbitals in each sell.

Chemical Elements				Electrons per shell or energy level
Symbol	Name	Electrons	Neutrons	1	2	3	4	5	6
H	Hydrogen	1	1	1	0
He	Helium	2	2	2	0
Li	Lithium	3	4	2	1
Be	Beryllium	4	5	2	2
B	Boron	5	6	2	3
C	Carbon	6	8	2	4
N	Nitrogen	7	7	2	5
O	Oxygen	8	8	2	6
F	Fluorine	9	10	2	7
Ne	Neon	10	10	2	8
Na	Sodium	11	12	2	8	1
Mg	Magnesium	12	12	2	8	2
Al	Aluminum	13	14	2	8	3
Si	Silicon	14	14	2	8	4
P	Phosphorus	15	16	2	8	5
S	Sulfur	16	16	2	8	6
Cl	Chlorine	17	18	2	8	7
Ar	Argon	18	22	2	8	8
K	Potassium	19	21	2	8	8	1
Ca	Calcium	20	20	2	8	8	2
Sc	Scandium	21	23	2	8	9	2
Ti	Titanium	22	26	2	8	10	2
V	Vanadium	23	28	2	8	11	2
Cr	Chromium	24	28	2	8	12	2
Mn	Manganese	25	30	2	8	13	2
Fe	Iron	26	30	2	8	14	2
Co	Cobalt	27	32	2	8	15	2
Ni	Nickel	28	31	2	8	16	2
Cu	Copper	29	35	2	8	17	2
Zn	Zinc	30	35	2	8	18	2
Ga	Gallium	31	39	2	8	18	3
Ge	Germanium	32	41	2	8	18	4
As	Arsenic	33	42	2	8	18	5
Se	Selenium	34	45	2	8	18	6
Br	Bromine	35	45	2	8	18	7
Kr	Krypton	36	48	2	8	18	8
Rb	Rubidium	37	48	2	8	18	8	1
Sr	Strontium	38	50	2	8	18	8	2
Y	Yttrium	39	50	2	8	18	9	2
Zr	Zirconium	40	51	2	8	18	10	2
Nb	Niobium	41	52	2	8	18	11	2
Mo	Molybdenum	42	54	2	8	18	12	2
Tc	Technetium	43	55	2	8	18	13	2
Ru	Ruthenium	44	57	2	8	18	14	2
Rh	Rhodium	45	58	2	8	18	15	2
Pd	Palladium	46	60	2	8	18	16	2
Ag	Silver	47	61	2	8	18	17	2
Cd	Cadmium	48	64	2	8	18	18	2
Ln	Indium	49	66	2	8	18	18	3
Sn	Tin	50	69	2	8	18	18	4
Sb	Antimony	51	71	2	8	18	18	5
Te	Tellurium	52	76	2	8	18	18	6
I	Iodine	53	74	2	8	18	18	7
Xe	Xenon	54	77	2	8	18	18	8
Cs	Cesium	55	78	2	8	18	18	8	1
Ba	Barium	56	81	2	8	18	18	8	2