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By Dawen Li, Shoieb Shaik and Scott Wehby

Big Science from the Small World of Atom

- Understanding Atomic Structure with 3D Visualization

Key Concepts: This module provides 8th grade middle school students a basic understanding of

the atomic structure. With the knowledge evolution of the atom structure, modern sciences

and technologies, particularly nanoscience and nanotechnology, have been revolutionarily

advanced. In this module development the structure of an atom and its constituents will be

demonstrated with the help of the 3D visualization and hands-on activities.

Materials supply:

Plastic atomic model with snap on electrons, protons and neutrons, periodic table

Softwares:

1) UNITY

2) Google Sketchup

ENGAGE and EXPLAIN: First do a survey in the classroom: “Everything in the universe is made

of particles so small that we cannot even see them. This particle is the smallest piece of matter

that still retains the property of one element. Anybody can tell me the name of this extremely

small particle? After students come up with the answer “Atom”, students will be asked to write

down a list of the various parts an atom comprises of. “What’s inside an atom? What are atoms

made up of?” Following the engagement questions, PowerPoint slides are used to explain the

evolution of human understanding of the atomic structure, and impart the basic knowledge

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about the atomic structure, the particles an atom is made up of, valence electrons and core

electrons, atomic number, atomic mass, and concepts of isotopes.

EXPLORE with Hands on Activities: A group of students will be provided with a periodic table

and an interactive atomic model kit, including snap-on particles representing electron, proton,

neutron, and box with shells based on Bohr model. Each snap-on will have the respective

charge representation on it. Electrons will have a negative (-) sign on it, a proton has (+) and

neutron has blank top.

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1) Explore atomic structures of different elements:

For each given element with atomic number in periodic table, students will be asked to

demonstrate atomic structure using atomic model kit. For instance, oxygen atom has atomic

number 8, which means it has 8 proton, 8 neutrons and 8 electrons. Students will make an

oxygen atom by placing 8 snap-on protons and 8 neutrons in the center of the atom

representing nucleus, and aligning 8 electrons in shells outside the nucleus based on periodic

table. Students will also be asked to show atomic structure for a few other elements, and

calculate number of valence electrons and core electrons.

In another instance, a design with the help of the interactive atomic model will be made to

represent a particular element. Based on the presence of number of electrons, protons and

neutrons, students will be asked to find out the element it represents from the periodic table.

2) Demonstration of concept of isotopes and ions:

With the interactive atomic model kit, the concept of isotopes will also be exposed to students.

Students will be shown how misbalancing the number of neutrons from protons gives rise to

isotopes. Boron isotopes, Boron-10 with 5 neutrons and Boron-11 with 6 neutrons, will be used

as an example to explore the concept of isotopes and calculate the average atomic mass.

For a given neutrally charged atoms, the number of protons and electrons is always equal.

What will happen if an atom loses or gains an electron? As a result, the atom is not electrically

neutral anymore. The atom is either positively or negatively charged, creating an ion. By

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presenting unbalanced number of electrons and protons in atomic model kit, students will be

asked to write down the element symbol with corresponding ion charges.

ELABORATE: This section aims to help students to further understand the hands-on activities

conducted in the explore part and element properties with the help of 3D visualizations of

periodic table. On clicking a particular element in the alive periodic table, the atomic structure

of the element, including the number of protons, neutrons and electrons, atomic mass, electron

occupation in the different shells (energy levels) so that the number of core electrons and the

valence electrons can be counted. Students will learn how elements are arranged in the

periodic table, how the number of valence electrons is correlated with group number in the

periodic table. Valence electrons are responsible for chemical bonding (chemical reaction),

while core electrons can be used to identify elements. With 3D visualization of X-ray

generation, students will be demonstrated how modern sciences and nanotechnology use

information from electrons to benefit mankind. Once a student picks up or clicks a specific

element, he should be able to give the atom structure information, such as atomic number,

number of protons, electrons (both core and valence electrons), mass number, etc.

Another elaborate activity is designed to help students build a methodology for scientific

research, which is employed in discovering atomic structure. In 1900s, scientists are not able to

see the atom, but they can find clues to infer what the atomic structure looks like. Their

discovering strategy includes recognize the problem, form the hypothesis, test and analyze the

data and draw conclusions. To practice this discovering strategy, each group of students will be

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provided with cents, quarters, stones and match sticks in zip-lock bags. Students place two of

four items in the envelope and seal it. After trading envelope with another group, students will

try to figure out what items are put inside the envelope without opening it. Record hypothesis

and see if the discovery about the contents of the envelop match your hypothesis. Think about

how you infer what you cannot observe from the envelope.

EVALUATE: Students’ understanding about the atomic structure will be assessed by following

questions:

1. What are different parts of an atom and draw its structure?

2. Where is the majority of the mass of atom located?

3. What are the particles that make up protons and neutrons?

4. Discuss the charge from an atom? How about charge from a proton, an electron and a

neutron?

5. Which element is an atom with 14 protons in the nucleus? What is the number of

valence and core electrons?

6. Why do elements in the same group undergo similar chemical properties?

7. How isotopes are defined? How to calculate number of neutrons?

8. What are the properties (metal or nonmetal, solid or gas phase) of the elements located

on the left side of the periodic table?

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Draw Conclusions

Test and Analyze Data

Form a Hypothesis

Recognize the Problem


9. Why are the noble gases in group VIII chemically stable?

10. Give a couple of examples on how electron beams are used in modern nanotechnology?

Background knowledge for teachers:

1. Elements: The presence of number of protons in an element defines the element.

Elements can have different number of neutrons (isotopes) and hence end up having

different mass numbers.

2. Atom: An atom is a smallest particle of the element that retains the characteristics of

that particular element. Basically all the available elements in the nature are made up of

tiny particles called atoms.

3. Protons: Proton is a fundamental constituent of atomic nuclei and comprises of one

unite positive charge. In a neutral atom, the number of protons is equal to the number

of electrons.

4. Electrons: Electrons are part of an atom that are negatively charged and moves around

the nucleus of an atom in orbits. An electron is much smaller than the proton and

neutron in size and mass. The presence of number of valence electrons determines how

they interact with other atoms.

5. Neutrons: Neutrons are elementary particles in the nucleus of an atom and essentially

have no charge. A neutron roughly holds the same mass as the proton in the nucleus.

6. Isotopes: Isotopes are atoms of the same element that have different number of

neutrons. The isotope of an atom is denoted by writing the element's name followed by

the sum of the number of protons and neutrons.

7. Valence electrons: Valence electrons are the electrons that are present in the outer

most shell of an atom and are responsible for the chemical bonding.

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8. Core electrons: Core electrons are the electrons in the inner shells of an atom and do

not participate in the chemical reaction. Core electrons can be used to generate X-rays

and identify elements.

9. Electronic configuration: The arrangement of the electrons at different shells (energy

level) and sublevels (orbits).

Atomic Structure Time line

Democritus

About 400 B.C. Greek philosopher Democritus proposed the idea that atoms make up all

substances

He named the smallest piece of matter “atomos,” meaning “not to be cut.”

However, a famous Greek philosopher, Aristotle, disputed Democritus’s theory.

Aristotle’s incorrect hypothesis was accepted for about 2000 years.

John Dalton

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In 1808, John Dalton, an English scientist, brought back the atom idea and proved atoms

exist by experiment.

All elements are composed of atoms, modeled as an indivisible sphere.

Atoms of the same element are exactly alike. Atoms of different elements are different.

J.J. Thomson

In 1897, an English scientist J.J. Thomson proposed a so called “Plum Pudding” model:

negatively charged electrons were scattered throughout a positively charged sphere,

like raisins in a pudding

Ernest Rutherford

In 1911, another English physicist Ernest Rutherford concluded from experiments that

almost all the mass of an atom, and all its positive charges, were concentrated in a

central atomic nucleus surrounding by electrons.

Niels Bohr

In 1903, Niels Bohr, a Danish scientist, put electrons into orbits.

He hypothesized that electrons travelled in a definite orbits around the nucleus at a

specific energy level, much like planets circle the sun.

James Chadwick, a student of Rutherford, concluded that the nucleus contained positive

protons and neutral neutrons.

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