Mole Day Items

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Mole Day Items

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Title: Mole Day Items

1
Mole Day Items

Q What happens when a mole bites a dog?
A He becomes Moleicious!
Q Why is it bad to tell mole jokes?
A It's mole-itically incorrect

2
Quiz

1) Compare Aristotles and Democrituss ideas
about Matter
2) Why was Aristotle held to be correct?
3) List 3 ideas from Daltons Atomic Theory
4) Who discovered electrons?
5) Draw a model of Thomsons atom.

6) Why did the existence of electrons account
for the existence of protons?
7) What allowed John Dalton to verify his atomic
theory?
8. Describe Rutherfords experiment thoroughly
9. Explain Rutherfords model of the atom
10. What did Millikan discover?
11. What do opposite charges do to each other?
12. What do like charges do to each other?

4
CP Chemistry September 29, 2005

1) Turn WS 3.1 in tray now
2) Review Study Guide
3) Test
4) HW Vocabulary Pages 111

5
Question 27

Distinguish between an endothermic and exothermic
reaction
After test, Vocabulary pg 111

6
CP Chemistry September 30, 2005

1) Turn in vocabulary (numbered) in box
2) Notes on Atomic Theory
3) Lab-Bunsen Burners
4) Last Quiz on Polyatomic Ions

7
Chemistry Unit 4Atomic Structure

Fall 2005
1st, 3rd, 4th Periods

8
Answer the following questions in your notes

1) Write your definition of an atom
2) If you could see atoms, sketch (or describe)
a model of the atom

9
Chapter Objectives

1. Discuss early theories about matter
2. Discuss the discovery of subatomic particles
3. Use terms such as mass number, atomic number,
atomic mass to describe elements

10
Early Theories About Matter

Democritus (460-370 BC)
Greek Philosopher
Around 420 BC, he proposed that matter was
discontinuous
There was some point at which matter could NOT be
divided further

11
Early Theories About Matter Cont.

Aristotle (384-322 BC)
Around 360 BC, he proposed matter was continuous
Matter could be subdivided indefinitely without
ever reaching a limit
He believed there was no ultimate underlying
structure to matter

12
Early Theories About Matter Cont.

Aristotles hypothesis was held to be correct
In ancient Greece, hypotheses were not tested
Hypotheses were accepted or rejected based on the
reputation of the philosopher

13
Early Theories About Matter Continued

In the 1500s and 1600s, a basic change in the way
science was done occurred.
Hypotheses were now TESTED!

14
Development of the Modern Atomic Theory

In 1782, a French chemist, Antoine Lavoisier
(1743-1794), made measurements of chemical change
in a sealed container.
He observed that the mass of reactants in the
container before a chemical reaction was equal to
the mass of the products after the reaction.

15
Development of the Modern Atomic Theory

Lavoisier concluded that when a chemical reaction
occurs, mass is neither created nor destroyed but
only changed.

Lavoisiers conclusion became known as the law of
conservation of mass.

16
Development of the Modern Atomic Theory
17
CP Chemistry October 4, 2005

1) Turn progress reports in box now
2) Notes on early atomic theory
3) Computer Activity Thomson Millikan
4) HW WS 4.1 Quiz 6 on polyatomics

18
Development of the Modern Atomic Theory

In 1799, another French chemist, Joseph Proust,
observed that the composition of water is always
11 percent hydrogen and 89 percent oxygen by
mass.

Regardless of the source of the water, it always
contains these same percentages of hydrogen and
oxygen.

19
Development of the Modern Atomic Theory

Proust studied many other compounds and observed
that the elements that composed the compounds
were always in a certain proportion by mass. This
principle is now referred to as the law of
definite proportions.

20
Daltons Atomic Theory

John Dalton (1766-1844), an English schoolteacher
and chemist, studied the results of experiments
by Lavoisier, Proust, and many other scientists.

21
Daltons Atomic Theory

John Dalton conducted various experiments and
formulated his atomic theory. He found that
1) All matter is composed of extremely small
particles called atoms

22
Daltons Atomic Theory Continued

2) Atoms of a given element are identical in
size, mass, and other properties atoms of
different elements differ in size, mass, and
other properties
3) Atoms cannot be subdivided, created, or
destroyed

23
Daltons Atomic Theory Continued

4) Atoms of different elements can combine in
simple, whole number ratios to form chemical
compounds
5) And finally, Dalton found that in chemical
reactions, atoms are combined, separated, or
rearranged

24
Daltons Atomic Theory Continued

Dalton was able to develop his theory based on
the invention of the chemical balance
Although his theory has been modified slightly to
accommodate new discoveries, Daltons theory was
so insightful that it has remained essentially
intact up to the present time.

25
Copy Answer in Notes

Answer the following questions on a separate
sheet of paper
1) Compare and contrast Democrituss and
Aristotles early theories about the atom
2) Which philosopher (Democritus or Aristotle)
was correct Hint Look at Daltons Atomic
Theory

26
Questions Continued

3) On what basis did Aristotle and Democritus
propose hypotheses about the nature of matter?
4) How did Daltons Atomic Theory differ from
Democrituss or Aristotles Theories?

27
Homework

Construct complete a chart with the following
1) Individuals Who Proposed Various Atomic
Theories
2) Approximate Date Theory Proposed
3) Theory
4) Description of Experiment Used
5) Any discoveries made
6) Other important information

28
Discovery of the Electron

Because of Daltons atomic theory, most
scientists in the 1800s believed that the atom
was like a tiny solid ball that could not be
broken up into parts.
In 1897, a British physicist, J.J. Thomson,
discovered that this solid-ball model was not
accurate.

29
JJ Thomsons Experiment

JJ Thomson (1856-1940)-British Physicist
Credited with discovery of electrons in 1897
Reasoned that negative particles resided in the
atom
He called these particles electrons

30
The Electron

Because of Daltons atomic theory, most
scientists in the 1800s believed that the atom
was like a tiny solid ball that could not be
broken up into parts.

In 1897, a British physicist, J.J. Thomson,
discovered that this solid-ball model was not
accurate.

Thomsons experiments used a vacuum tube.

31
The Electron

A vacuum tube has had all gases pumped out of it.

At each end of the tube is a metal piece called
an electrode, which is connected through the
glass to a metal terminal outside the tube.

These electrodes become electrically charged when
they are connected to a high-voltage electrical
source.

32
Cathode-Ray Tube

When the electrodes are charged, rays travel in
the tube from the negative electrode, which is
the cathode, to the positive electrode, the
anode.

Because these rays originate at the cathode, they
are called cathode rays.

33
Video of Thomsons Experiment
Click box to view movie clip.
34
Cathode-Ray Tube

Thomson found that the rays bent toward a
positively charged plate and away from a
negatively charged plate.

He knew that objects with like charges repel each
other, and objects with unlike charges attract
each other.

35
Cathode-Ray Tube

Thomson concluded that cathode rays are made up
of invisible, negatively charged particles
referred to as electrons.

These electrons had to come from the matter
(atoms) of the negative electrode.

36
Animation of Thomsons Experiment

http//www.dlt.ncssm.edu/core/Chapter3-Atomic_Str_
20Part1/Chapter3-Animations/Canal_Ray-CRT.html

He reasoned that since atoms are NEUTRAL, there
must be some positive charge to balance out this
negative charge
He proposed a dense cloud of positive charge with
the negative charge randomly embedded within the
cloud
His model is called the plum pudding model
Similar to a pepperoni pizza model

38
Thomsons Plum Pudding Model
The dense cloud of positive charge
39
Thomsons Experiment

1) What did he discover?
2) In what year did he make his discovery?
3) Adequately describe the experiment that he
used.
4) How did his discovery support or disprove
Daltons atomic theory?

40
Thomsons Experiment

5) Why were the electrons in the cathode tube
attracted to the positive plates?
6) Draw a model of what Thomson believed the
atom looked like.

41
Millikans Oil Drop Experiment

Robert Millikan (1868-1953)
American scientist, University of Chicago
Discovered the charge on an electron using the
oil drop experiment

42
Animation of Millikans Experiment

http//www.dlt.ncssm.edu/core/Chapter3-Atomic_Str_
20Part1/Chapter3-Animations/OilDrop.html

43
Millikans Experiment

Liquid goes through an atomizer to produce
droplets
These droplets enter a chamber
The bottom of the chamber has a hole in the
center
The droplets fall through the hole due to gravity

An electrical field is produced using electricity
This field offsets the effect of gravity causing
the droplets to be suspended in mid air
Through a series of known relationships and
mathematical equations, Millikan calculates the
charge of the electron in Coulombs.

Thomsons and Millikans work allowed for the
mass of the electron to be determined using known
relationships and equations

46
CP Chemistry October 5, 2005

1) Review Polyatomic Ions Quiz
2) Review of Notes
3) Notes on Chadwick Rutherford
4) CW WS 4.1
5) HW Quiz on Notes

47
Discovery of Neutron

James Chadwick (1891-1974) is credited with the
discovery of the neutron in 1932

48
Rutherfords Model of the Atom

Ernest Rutherford (1871-1937) from New Zealand
Thomsons atomic model had not yet been tested
due to the tiny size of the atom

49
Rutherfords Model of the Atom

Rutherford had been studying radioactivity
In 1911, he bombarded a thin sheet of metal with
alpha particles
Alpha particles are positively charged

50
The Gold Foil Experiment
51

http//micro.magnet.fsu.edu/electromag/java/ruther
ford/

52
Video of Rutherfords Experiment
Click box to view movie clip.
53

If Thomsons plum pudding model was correct, he
expected the alpha particles to crash through the
gold foil (with only minor deflections)
He placed a screen around the foil. After the
alpha particles passed through the gold foil,
they would light up the screen. Most of the
particles should pass through unaffected

54
Rutherfords Results

Some of the alpha particles passed through and
hit the screen as predicted
BUT a high number of alpha particles were
deflected. This indicated that there must be
something in the center of the atom that caused
deflection

55
Rutherfords Conclusion

He reasoned that a positive charge center rested
in the atom
He called this center the nucleus

56
CP Chemistry October 6, 2005

1) Review for Quiz
2) Quiz
3) Notes on Atoms Its particles
4) CW WS 4.3
5) HW WS 4.4

57
Thomsons Movie
58
Video of Rutherfords Experiment
Click box to view movie clip.
59
Rutherfords Experiment
60
Neils Bohrs Model

His model is called the solar systemmodel
The center of the atom contains protons and
neutrons
This area is collectively called the nucleus
The electrons orbit around the nucleus like the
planets do the sun

61
Question (copy and answer in your notes)

The planets orbit around the sun due to gravity.
Why do electrons orbit the nucleus?

62
The Three Subatomic Particles

After various molecular models of the atoms had
been tested, it was determined that three
subatomic particles made up the atom
Protons
Neutrons
Electrons

63
Protons

Protons are found in the nucleus
Protons have an actual charge of 1.6 x 10-19 C
and a relative charge of 1
The actual mass of a proton is 1.67 x 10-24 g
The relative mass of a proton is 1 atomic mass
unit (amu)
The symbol is p

64
Neutrons

Neutrons are found in the nucleus
Neutrons have an actual charge of 0 C and a
relative charge of 0
The actual mass of a neutron is 1.67 x 10-24 g
The relative mass of a neutron is 1 atomic mass
unit (amu)
The symbol is n0

65
Electrons

Electrons are found outside the nucleus
Electrons have an actual charge of -1.6 x 10-19 C
and a relative charge of -1
The actual mass of an electron is 9.11 x 10-28 g

66
4th Period
67
Electrons

The relative mass of a electron is 1/1840 atomic
mass unit (amu)
The electron has a very small mass
The symbol is e-

68
CP Chemistry October 7, 2005

1) Notes on atomic and mass numbers
2) Notes on nuclide symbols
3) Notes on average atomic mass
4) Lab

69
Nuclear Forces

Neutrons exert an attraction toward protons and
other neutrons
Overall the forces produce enough attraction to
keep protons relative close together in the
nucleus

70
Nuclear Forces

Neutrons exert an attraction toward protons and
other neutrons
Overall the forces produce enough attraction to
keep protons relative close together in the
nucleus

71
Construct and complete a chart with the following
information

List the particles of the atoms
List the particles location in the atom
List the relative and actual charge of the
particle
List the relative and actual mass of the
particles
List the symbol of the particle

72
Atomic Number

Each element has a certain number of protons in
its nucleus
The number of protons in the nucleus is called
the atomic number
Each element has its own atomic number because
each element has its own, unique number of protons

An element has certain chemical properties based
on the number of protons in its nucleus
Elements are numbered in the periodic table based
on the atomic number
Example If an element has two protons, what is
its atomic number? What is the identity of the
element?

74
On Your Own

Which element has
a) 12 protons
b) 35 protons
c) 50 protons
d) 92 protons

Since atoms are neutral, the number of protons
must equal the number of electrons
Example If an element (atom) has 7 electrons,
how many protons does it have? What is the
elements identity?

On Your Own
Determine the number of protons in the following
atoms as well as each atoms identity
a) 6 electrons b) 14 electrons
c) 72 electrons d) 55 electrons

77
Mass Number

Mass Number the number of protons and neutrons
in an atom added together
Mathematically
Mass Number Protons Neutrons

78
Example

What is the mass number of an atom with 16
protons and 16 neutrons?

79
On Your Own

Determine the Mass Number for the following atoms
a) 17 protons and 18 neutrons
b) 11 protons and 12 neutrons
c) 1 proton and NO neutrons
d) 3 protons and 4 neutrons

80
Nuclide Symbols

Mass Numbers are written in the upper left
preceding the chemical symbol
Atomic Number is written directly under the mass
number

Example Write the correct nuclide symbol for an
element with 79 p and 118 n0

Mass Number
197
Au
Element Symbol
79
Atomic Number
82
Copy and Answer in Notes

1. List the three subatomic particles, their
relative charge, relative mass, and location
2. What does atomic number mean?
3. What atom has an atomic number of 32?
4. Determine the number of protons and electrons
ina. Ne b. Po c. Pt

83
CP Chemistry October 10, 2005

1) Review Mass Atomic Number
2) Notes on Isotopes
3) Notes on Calculating Avg. Atomic Mass
4) Lab Candium
5) HW WS 4.4, Study Guide, Practice Que
6) Test - Wednesday

84
Review-Complete the chart
85
Mole Day Items

Q What happens when a mole bites a dog?
A He becomes Moleicious!
Q Why is it bad to tell mole jokes?
A It's mole-itically incorrect

86
Isotopes

Atoms of the same elements have the same number
of protons
HOWEVER there may be different numbers of neutrons

87
Isotopes

When an elements atom has different numbers of
neutrons, it is said to have isotopes
Isotopes are common in nature

88
Hydrogens Three Isotopes

Hydrogen has the following isotopes
Protium-a hydrogen atom with one proton and NO
neutrons

89
Hydrogens Three Isotopes

Deuterium-a hydrogen atom with one proton and
only one neutron
Tritium-a hydrogen atom with one proton and two
neutrons

90
On Your Own

Determine the mass and atomic numbers for each of
hydrogens isotopes. Put this information into
nuclide symbol form

91
Average Atomic Mass

Atomic mass is the mass of an atom expressed in
atomic mass units or amu
The atomic mass unit is based in relation to the
standard of carbon-12

92
Average Atomic Mass Continued

Carbon-12 has a mass of 12.000 00 amu
If an atoms weighs half as much as carbon-12, its
atomic mass will be 6.000 00 amu

If an atom weighs four times as much as
carbon-12, it will have a mass of 48.000 00 amu
The atomic mass that is reported in the periodic
table is a weighted average based on the relative
abundance of each element

94
Review - Answer in Notes

1. What mass would an atom have that has a mass
equal to 1/12 that of carbon-12? What element is
this?
2. Determine the mass each atom would have if
a. It weighed 12 times as much as C-12
b. It weighed 3/17 as much as C-12
3. How do all isotopes differ from each other?

Relative abundance refers to how commonly the
isotope occurs in nature
Certain isotopes will occur more commonly than
other isotopes

96
To Determine Avg. Atomic Mass

1) First convert relative abundance () to
decimal equivalent
2) Multiply mass (in amu) by decimal equivalent
3) Add the numbers together
4) The sum (in amu) is the average atomic mass

97
7th Period POP QUIZ

The average atomic mass for an element is 20.0
amu. It only has 2 naturally occurring isotopes.
The mass of isotope 1 is 15.0 amu and isotope
2 is 30 amu. Find the relative abundance of
each isotope.

98
CP Chemistry October 11, 2005

1) Review Isotopes
2) Problems with Avg. Atomic Mass
3) Review for Test
4) Practice EOC Questions
5) HW Finish Study Guide

99
Copy Answer in Notes

1. What is an isotope?
2. How is mass number different from atomic
number?
3. How is relative () abundance determined?

100
Quiz Complete the Chart Below
101

For example, an element has two naturally
occurring isotopes. One isotope has a relative
abundance of 19.91 and a mass of 10.012 amu. A
second isotope has a relative abundance of
80.08 and a mass of 11.009 amu. Calculate the
atomic mass

102
Additional Example