Download Atomic Structure

What do these things have in common?
• A road-side diner
• Lincoln assassin
• Early Superman costume changes
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Inquiry Activity “Electric Charge”
Models in Science
Notes Ch 4.1 “Defining the Atom”
Assignments:
Materials: Four 25 cm pieces of tape, ruler
Procedure:
1. Stick 2 of the pieces to your desk 10 cm apart. Leave 2-3
cm hanging off the desk. Yank tape off the desk and hold the
pieces close together. What happens?
2. Slide the other two pieces of tape through your fingers a
few times and hold them close together. What happens?
Procedure Cont’d
3. What would happen if you held the two different tapes
close together? Try it!
4. Do both groups of tape have the same charge? Explain.
Chapter 4 is about atomic structure. It uses the word model a
lot.
1. What is a model?
2. What are three examples of models?
Science has taught us how to put the atom to work. But to make it work for
good instead of for evil lies in the domain dealing with the principles of
human duty. We are now facing a problem more of ethics than physics.
Barnard Baruch to Atomic Energy Commission June, 1946

Compare and contrast atomic models.
Early Models of the Atom
▪ An atom is the smallest particle of an element that
retains its identity in a chemical reaction.
▪ Philosophers and scientists have proposed many
ideas on the structure of atoms.
Democritus‘ Atomic Philosophy
Democritus, a Greek philosopher 460-370 B.C.
4.1
Democritus believed that atoms were
indivisible and indestructible.
Limitations:
▪didn’t explain chemical behavior
▪lacked experimental support.
Democritus’ model of
the atom.
4.1
Dalton’s Atomic Theory
English chemist and school teacher (1766-
1844)
Built on Democritus’s ideas with experiments
and data.
4.1
Dalton’s Theory
1. All elements are composed of tiny indivisible
particles called atoms.
4.1
Dalton’s Theory
2. Atoms of the same element are identical. The
atoms of any one element are different from those of
any other element.
4.1
Dalton’s Theory
3. Atoms of different elements can… physically mix or
chemically combine to form compounds.
4.1
Dalton’s Theory
4. Chemicals can separate, join, or rearrange
atoms. They are NEVER changed into atoms of
another element in a chemical reaction.
4.1
Sizing up the Atom
Despite their small size, individual atoms can
be seen with instruments like scanning
tunneling microscopes.
STMs use differences in electric voltage to
image atoms like this iron.
1. The ancient Greek philosopher credited with
suggesting all matter is made of indivisible atoms is
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Plato.
Aristotle.
Democritus.
Socrates.
2. Dalton's atomic theory improved earlier atomic
theory by
 teaching that all matter is composed of tiny particles
called atoms.
 theorizing that all atoms of the same element are
identical.
 using experimental methods to establish a scientific
theory.
 not relating atoms to chemical change.
3. Individual atoms are observable with
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the naked eye.
a magnifying glass.
a light microscope.
a scanning tunneling microscope.
According to Dalton’s Theory, what is wrong
with these statements?
1. All atoms are identical.
2. Chemical reactions happen when atoms of
one element change into atoms of another
element.
A 63.5 g sample of copper contains 6.02 x 1023
atoms. What is the mass of one copper atom?
63.5 g / (6.02 x 1023 atoms)
1.05 x 10-22 g
Remember 6.02 x 1023 , it will come back to haunt you…
Gina was making apricot jam. She cooked
them but forgot she needed 1 ounce of lemon
juice for every 2 apricots.
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How can she figure out how much lemon
juice to add?
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How far can a dog run into the woods? Why?
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Notes Ch 4.2 “Nuclear Atom”
Black Box Activity
EC
Assignments:
1. SR 4.1-4.2 due TODAY
Objectives:
 Identify three major types of subatomic
particles.
 Compare/contrast atomic models (Dalton,
Thomson, Rutherford)
4.2
Cathode-ray tubes are
found in TVs,
computer monitors,
and many other
devices with electronic
displays.
4.2
Scientists after Dalton discovered atoms
AREN’T indivisible.
3
Subatomic Particles
electrons
protons
neutrons
Bohr’s “planetary model” 1915
4.2
Electrons
▪ In 1897, the English physicist J. J. Thomson (1856–
1940) discovered negatively charged particles… the
electron.
Thomson is also credited
with discovering isotopes.
4.2
Thomson’s Cathode Ray Experiments

Passed electric current through gases at
low pressure.
 The result was a glowing beam, or cathode
ray, that traveled from the cathode to the
anode.
4.2
▪ Cathode Ray Tube
4.2
▪ A cathode ray is deflected by a magnet.
4.2
▪ A cathode ray is deflected by electrically charged
plates.
4.2
Protons

In 1886, Eugen Goldstein (1850–1930) found rays
traveling opposite to the cathode rays. He concluded
that they were composed of positive particles.
These
positively charged subatomic particles are called
protons.
4.2
Neutrons
 In 1932, the English physicist James
Chadwick (1891–1974) confirmed the
existence of yet another subatomic particle:
the neutron.
 Neutrons are neutral subatomic particles with
a mass nearly equal to that of a proton.
4.2
Masses and Charges of the 3 Basic
Subatomic Particles
4.2
Models since Dalton
 Thomson’s model of the atom was filled with
positively charged material and the electrons
were evenly distributed throughout.
 aka “plum pudding” model
Thomson’s “plum pudding”
model, 1904.
4.2

Thomson’s model was short lived…
4.2
Rutherford’s Gold-Foil Experiment
▪ In 1911, Rutherford and his coworkers at the
University of Manchester, England, directed a
narrow beam of alpha particles at a very thin sheet
of gold foil.
Alpha particles = helium atoms with electrons
stripped. They are relatively safe.
4.2
▪ Rutherford’s Gold-Foil Experiment
4.2
▪ Alpha particles scatter from the gold foil.
What caused these deflections? Hint: What is the charge on alpha particles?
4.2
The Rutherford Atomic Model
▪ He concluded the atom is mostly empty space.
▪ All the positive charge and almost all of the mass
are concentrated in a small region.
▪ The nucleus is the tiny central core of an atom and
is composed of protons and neutrons.
4.2
Rutherford’s Model… 1911
 1. Which of the following is NOT an example of a
subatomic particle?
▪
▪
▪
▪
proton
molecule
electron
neutron
 2. The nucleus of an atom consists of
▪ electrons only.
▪ protons only.
▪ protons and neutrons.
▪ electrons and neutrons.
 3. Most of the volume of the atom is occupied by
the
▪
▪
▪
▪
electrons.
neutrons.
protons and neutrons.
protons.
1. What was Rutherford's gold foil experiment?
2. How are your black boxes similar to
Rutherford's experiments?
3. How is this activity different?
Build your own black box to torment fellow chemistry students!
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BB object ideas… dice, coins, ping pong balls, paper clips,
etc.
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String – It comes in, it goes out, but who knows what it does
in the middle.
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DUE – FRIDAY October 2 for up to 15 points.
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Quarter ends Thurs, Oct. 8
All 1st Quarter assignments MUST be in by
Tues, Oct 6
EC Available
 Bell Work
 Project LEAP participation
 TED.com videos
▪ Up to 5 pts each, can do 3
▪ Watch video and include title and speaker, PARAGRAPH
summary, and PARAGRAPH personal reaction
Shadow was examining a 14 ½ degree angle
using his magnifying glass that makes things 2
times bigger.
Under the glass, how large would the angle
measure?
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Grade Reports home
Galileo Benchmarks
 Scored out of topics covered.
 TRY!!
Assignments:
1. SR 4.1-4.2 LATE
Mr. and Mrs. Plum have six daughters and each
daughter has one brother.
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Provided there are no socially questionable
relationships, what is the fewest number of
people are in the Plum family?
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Finish Galileo Benchmarks
 Scored out of topics covered.
 TRY!!
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Notes Ch 4.3 “Distinguishing Among Atoms”
SR 4.3 due MONDAY
Assignments:
1. SR 4.1-4.2 LATE
2. Letter Home - THURS
3. SR 4.3 due MONDAY
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How would the results of Rutherford's
experiments have been different if atoms had
the positive charges on the outside and
negative charges in the middle?
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Why?
Objectives
 Explain what makes elements and isotopes
different from each other.
 Calculate the numbers of protons, neutrons,
and electrons in an atom.
 Explain why chemists use the Periodic Table.
4.3
Apples, dogs, cats,
horses, etc all come in
different varieties.
So do elements.
4.3
Atomic
Number
Elements are different because they contain
different numbers of protons.
Atomic number = # of protons.
Atoms are neutral, so this is also the number
of electrons.
4.3
Use the atomic number to figure it
out.
Copy and complete the table in your note book. There WILL be things like this
on your test!
4.3
Mass
Number is …
▪ The total number of protons and neutrons in an
atom.
4.3

Mass numbers and atomic numbers are
often written like this.
Mass Number
Atomic Number
4.3
Isotopes
▪ Isotopes are atoms that have the same number of
protons but different numbers of neutrons.
▪They have different mass numbers, and may have
different properties.
▪ Can write as either element or symbol – mass
▪Hydrogen-1
▪H-2
▪H-3
4.3
▪ Isotopes will react the same because they have
identical numbers of protons and electrons.
Read’em and Reap wants to give away coloring
books. They’ve created a puzzle, so they don’t
have to give away too many.
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The first week of a month without an A in it.
On a day of the week with a U in it.
The month has no E, but the day does.
When will they give away the coloring books?
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Notes Ch 4.3 “Distinguishing Among Atoms”
SR 4.3 due TUESDAY
ALL assignments so far MUST be in
by TUESDAY at 3:30 pm for credit!
Assignments:
1. SR 4.1-4.2 LATE
2. Letter Home - LATE
3. SR 4.3 due TUESDAY
Ch 4 “Atoms” test THURSDAY (2nd Q
Grade)
Practice Problems
Calculate the number of neutrons in the following
radioactive isotopes.
14 C
6
40 K
19
238
92U
99 Mo
42
1. What elements are they?
2.
How are these isotopes named?
3. Why are these isotopes chemically the same
as the non-radioactive ones?
4.3
Atomic
Mass
▪ An atomic mass unit (amu) is defined as one
twelfth of the mass of a carbon-12 atom.
▪ C-12 is the reference isotope. It has a mass of
exactly 12 amu.
▪ There are 12 particles in the nucleus of a C-12
atom, so…
1 amu = mass of proton or neutron.
4.3
▪ Some Elements and Their Isotopes
4.3

Atomic Mass
 Weighted average mass of the atoms in a
naturally occurring sample of the element.
▪ Reflects the mass and the relative abundance of the
isotopes.
4.3
▪ Weighted Average Mass of a Chlorine Atom
4.3
Calculating Atomic
Mass
 Multiply the mass of each isotope by its
natural abundance as a decimal, and then
add the products.
4.3
Example: carbon has two stable isotopes:
▪ Carbon-12, which has a natural abundance of
98.89%
▪ Carbon-13, which has a natural abundance of
1.11%.
4.3
The
Periodic Table
▪ Elements are arranged groups based on a set of
repeating properties.
▪ Modern PTs are arranged by atomic number.
▪Elements or groups are easily compared.
4.3
▪ The Periodic Table
4.3

Periodic Table Vocab
 Period: Each horizontal row
 The properties of the elements vary as you
move across it from element to element.
4.3
▪ A Period
4.3

Periodic Table Vocab
 Group: Each vertical column of the periodic
table (family).
 Elements have similar chemical and physical
properties.
4.3
▪ A Group or Family
Gravity on Mars is one-seventh what it is on Earth.
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How much do you weigh on Earth? How much would you
weigh on Mars?
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Review Ch 4.3 “Distinguishing”
SR 4.3 due TODAY!
Mass of Vegium Lab
Ch 4 Practice Problems due THURSDAY
ALL assignments so far MUST be in
by TODAYat 3:30 pm for credit!
Assignments:
1. SR 4.1-4.2 LATE
2. Letter Home - LATE
3. SR 4.3 due TUESDAY
Ch 4 “Atoms” test THURSDAY (2nd Q
Grade)
1. Isotopes of an element have
▪ the same mass number.
▪ different atomic numbers.
▪ the same number of protons but different numbers of
neutrons.
▪ the same number of protons but different numbers of
electrons.
2. How many neutrons are in sulfur-33?
▪
▪
▪
▪
16 neutrons
33 neutrons
17 neutrons
32.06 neutrons
3. If sulfur contained 90.0% sulfur-32 and 10.0%
sulfur-34, its atomic mass would be
▪
▪
▪
▪
32.2 amu.
32.4 amu.
33.0 amu.
35.4 amu.
Two mothers and two daughters go shopping. They have 21 $1
bills which they split so each got $7.
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How is this possible?
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Mass of Vegium Lab
Ch 4 Practice Problems due THURSDAY
Ch 4 “Atoms” test THURSDAY (2nd Q
Grade)
Assignments:
1.
Pick a theme for your timeline (ie spies, aliens, story…)
2.
Look through Ch 4.1-2 and your notes.
3.
Put the philosophers/scientists and their contributions to
atomic theory on a timeline. Include atomic models, if
relevant.
- Democritus
- Rutherford
- Chadwick
- Millikan
- Goldstein
- Thomson
- Dalton

Compare and contrast Thomson’s and Rutherford’s atomic
models.

Find the numbers of protons, neutrons, and electrons in
the following elements. Then name the most common
isotope of each.
 rubidium
 rutherfordium

- tellurium
- titanium
What information would you need to calculate the atomic
masses listed on the Periodic Table?