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Chemistry Unit 2 Topic 1 Atomic Structure
ACT-CORE Atomic Theory Gallery Walk
TEKS
C. 5 A explain the use of chemical and physical properties in the historical development of the Periodic Table
C. 6 A understand the experimental design and conclusions used in the development of modern atomic theory,
including Dalton's Postulates, Thomson's discovery of electron properties, Rutherford's nuclear atom, and
Bohr's nuclear atom
KUD
Understand that the models and tools of chemistry are a result of the dynamic contributions of scientists over time.
Know the sequence of discoveries of subatomic particles, the responsible scientist, and what they discovered.
Know the contribution of each scientist and the progression of the modern atomic model.
Know the parts of an atom are the nucleus, electron cloud, proton, neutron, electron, and valence electrons.
Materials
ACT-CORE Atomic Theory Gallery Walk Student Page one (1) per student
Atomic Theory Gallery Walk Rotation Cards/Pages (1-2 sets per class)
Procedure
Teacher Activity Setup
1. Print out and set up stations of the Atomic Theory Gallery Walk Rotation Cards/Pages. The station will need
nothing more than the rotation card/page itself. Depending on the size of the class, the teacher may want
to have more than one copy of these available. Laminating the cards/pages is recommended to extend the
life of the pages/cards.
2. This activity can be managed several ways depending on the preference of the teacher. The students can
work independently in small groups at their own pace, or the teacher can manage this activity as a rotation
activity with students working in small groups and each station given a particular amount of time.
Warm-up
1. This time can be used to give students a warm-up of your choice that reflects the needs of your particular
students, or it can be used to review/complete yesterday’s content.
Activity
1. Distribute the ACT-CORE Atomic Theory Gallery Walk Student Page one (1) to each student.
2. Explain the management method you have chosen. Remind the students to record their answers on their
student sheet and to use their notes as necessary. As students are working, the teacher should be
circulating the room to ensure that students are on task and to provide help as necessary.
3. Be sure that the students go back and answer question 5 of station one after they answer the questions at
alll of the stations.
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Chemistry Unit 2 Topic 1 Atomic Structure
Station 1—John Dalton
1766-1844
John Dalton was an English chemist. His ideas formed the atomic
theory of matter. Here are his ideas:
1. All elements are composed (made up) of atoms. It is impossible
to divide or destroy an atom.
2. All atoms of the same elements are alike. (One atom of oxygen
is like another atom of oxygen.)
3. Atoms of different elements are different. (An atom of oxygen is
different from an
atom of hydrogen.)
4. Atoms of different
form a compound. These atoms have to be in
ratios. For example, water is a compound
hydrogen and 1 atom of oxygen (a ratio of
hydrogen and 2 atoms of oxygen cannot
water.
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elements combine to
definite whole number
made up of 2 atoms of
2:1). Three atoms of
combine to make
Chemistry Unit 2 Topic 1 Atomic Structure
Station 2—J.J. Thompson (Gas tube experiment)
Late 1800s
J.J. Thompson was an English scientist. He discovered the electron when he was
experimenting with gas discharge tubes. He noticed a movement in a tube. He called the
movement cathode rays. The rays moved from the negative end of the tube to the
positive end. He realized that the rays were rays were made of negatively charged
particles that he called electrons. His theory also has been call the “plum-pudding” model
of the atom.
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Chemistry Unit 2 Topic 1 Atomic Structure
Station 3—Lord Ernest Rutherford
1871-1937
Ernest Rutherford conducted a famous experiment called the gold foil experiment. He
took a thin sheet of gold foil. He used special equipment to shoot alpha particles
(positively charged particles) at the gold foil. Most particles passed straight through the
foil like the foil was not there. Some particles went straight back or were deflected (went
in another direction) as if they had hit something. The experiment shows:
• Atoms are made of a small positive
nucleus; positive nucleus repels
(pushes away) positive alpha particles;
• Atoms are mostly empty space.
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Chemistry Unit 2 Topic 1 Atomic Structure
Station 4—Niels Bohr
Early 1900s
Niels Bohr was a Danish physicist. He proposed a model of the atom that is similar to the
model of the solar system. The electrons go around the nucleus like planets orbit around
the sun. All electrons have their energy levels – a certain distance from the nucleus. Each
energy level can hold a certain number of electrons.
Level 1 can hold 2 electrons
Level 2– 8 electrons
Level 3 – 18 electrons
Level 4 – 32 electrons
The energy of electrons goes up from Level 1 to other
levels. When electrons release (lose) energy they go
down a level. When electrons absorb (gain) energy,
they go to a higher level.
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Chemistry Unit 2 Topic 1 Atomic Structure
Station 5—James Chadwick
1932
Since Thomson's discovery of the electron in 1897, scientists
had realized that an atom must contain a positive charge to
counterbalance the electrons' negative charge. In 1919, as a
byproduct of his experiments on the splitting of atomic
nuclei, Rutherford discovered the proton, which constitutes
the nucleus of a hydrogen atom. Although Rutherford
proposed the existence of a neutral subatomic particle in 1920, the actual discovery was
made by English physicist James Chadwick, a former student of Rutherford, in 1932.
Chadwick found that:
1.
When working with isotopes, the mass of atom was not always exactly the same.
This was due to the presence of another particle in the nucleus called a neutron.
2.
A neutron has about the same mass as a proton.
3.
A neutron has no electrical charge (is neutral).
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Chemistry Unit 2 Topic 1 Atomic Structure
Station 6—Structure of the Atom
Scientists described the atom as having a small central region containing over 99% of its mass. This
region is called the nucleus. Around the nucleus move very small particles called electrons, which
have an electrical charge of -1.
Part of the atom:
1.
The nucleus contains two type of particles: protons and
neutrons, and makes up the mass of the atom.
2.
Protons have a positive charge (+1) and identify the element.
3.
Neutrons have no charge or are neutral.
4.
Electrons have a negative (-1) charge and are located around
the nucleus in an area called the electron cloud.
Two numbers are used to describe the components of an atom.
1.
The atomic number is the number of protons in an atom. The number of protons is the
identifying characteristic of an atom and DOES NOT change. The atomic number is found on the
periodic table.
2.
The mass number is equal to the number of protons and neutrons in the nucleus.
RISD Curriculum & Instruction
Chemistry Unit 2 Topic 1 Atomic Structure
ACT-CORE Atomic Theory Gallery Walk—Student Page
Name _____________________________________________________
Directions: At each station, you will find information about the scientific discoveries related to the
modern atomic theory. Read the information provided and answer the questions below.
Station1—John Dalton
1. What is the name of his theory? ______________________________________________________
2. What are elements made of? ______________________________________________________
3. According to Dalton’s theory, why are carbon and oxygen different elements? ___________________________
_____________________________________________________________________________________________
4. The ratio of atoms in HCl is
a. 1:3
b. 2:1
c. 1:1
5. Which of Dalton theories is no longer true?___________________________________________
(answer this after you get all the information from other station)
Station 2—J.J. Thompson (Gas tube experiment)
1. What did J.J. Thompson discover? ______________________________________________________
2. What is the charge of an electron?______________________________________________________
3. What are cathode rays made of?________________________________________________________
4. Why do electrons move from the negative end of the tube to the positive end? ___________________________
_____________________________________________________________________________________________
Station 3—James Chadwick
1.
What did Chadwick discover?________________
2.
What is the charge of a neutron?______________
3.
Where can you find a neutron?________________
4.
How did Chadwick know that neutrons must exist in the nucleus? ________________________________
_____________________________________________________________________________________________
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Chemistry Unit 2 Topic 1 Atomic Structure
Station 4—Lord Ernest Rutherford
1. What is the charge of an alpha particle?______________________________________________________
2. Why is Rutherford’s experiment called the gold foil experiment? __________________________________
________________________________________________________________________________________
3. What happened to the alpha particles as they hit the gold foil?___________________________________
________________________________________________________________________________________
4. How did he know that the nucleus was positively charged? __________________________________________
____________________________________________________________________________________________
Station 5—Niels Bohr
1. Why could Bohr’s model be called a planetary model of the atom? _____________________________________
_____________________________________________________________________________________________
2. How many electrons can the fourth energy level hold?
______________________________________________________
3. Would an electron have to absorb or release energy to jump from the second energy level to the third energy
level? ______________________________________________________
Station 6—Structure of the Atom
1.
What do scientists call the center region of an atom?_________
2.
What can be found in the nucleus of an atom?_______________
3.
Where can you find electrons in an atom?_________
4.
And what is the charge of an electron?_________
5.
What does the atomic number of an element tell you? __________________________________________
6.
Where do you find the atomic number? ____________________________________
7.
Does the atomic number of an atom change?__________________________
8.
Why or why not? ________________________________________________________________________
9.
What is the formula to find the mass number?_________________________________________________
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