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The Structure of the Atom. Chap. 4. I. History. I. History. A. Early Greeks. Explain matter with 4 ‘elements’. I. History. A. Early Greeks. 1. Air 2. Earth 3. Fire 4. Water. Explain matter with 4 ‘elements’. I. History. A. Early Greeks B. Democritus.

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slide3
I. History

A. Early Greeks

Explain matter with 4 ‘elements’

slide4
I. History

A. Early Greeks

1. Air

2. Earth

3. Fire

4. Water

Explain matter with 4 ‘elements’

slide5
I. History

A. Early Greeks

B. Democritus

Greek philosopher who first introduced concept of ‘atomos’

slide6
I. History

A. Early Greeks

B. Democritus

C. Alchemists

Devoted to making precious metals from base metals

slide7
I. History

A. Early Greeks

B. Democritus

C. Alchemists

D. Dalton

Formulated the ‘Atomic Theory of Matter’

slide8
Atomic Theory of Matter

1. All matter is made of . . .

slide9
Atomic Theory of Matter

1. All matter is made of . . .

2. Atoms cannot be . . .

slide10
Atomic Theory of Matter

1. All matter is made of . . .

2. Atoms cannot be . . .

3. Atoms of a given element . . .

slide11
Atomic Theory of Matter

1. All matter is made of . . .

2. Atoms cannot be . . .

3. Atoms of a given element . . .

4. Atoms of 2 different elements . .

slide12
Atomic Theory of Matter

1. All matter is made of . . .

2. Atoms cannot be . . .

3. Atoms of a given element . . .

4. Atoms of different elements . . .

5. In a chemical reaction atoms are

slide13
I. History
  • A. Early Greeks
  • B. Democritus
  • C. Alchemists
  • Dalton
  • Definition of Atom
slide14
Atom

The smallest particle of an element that retains properties of that element.

slide15
II. Discoveries of atoms
  • J.J. Thomson – 1890s

Used a cathode ray tube (CRT) to measure the charge:mass ratio of an electron

slide16
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • chg:mass =
  • 1.76 x 1011 C/kg
slide17
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • chg:mass =
  • 1.76 x 1011 C/kg
  • Discovery led to plum-pudding model
slide18
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • Robert Millikan - 1909

Measured the charge of an electron in his ‘oil drop’ exper.

slide19
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • Robert Millikan - 1909
  • Charge = 1.6 x 10-19
slide20
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • Robert Millikan - 1909
  • Rutherford - 1911

Discovered nucleus in gold-foil experiment

slide21
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • Robert Millikan - 1909
  • Rutherford - 1911
  • Fired alpha particles at thin metal sheet.
slide22
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • Robert Millikan - 1909
  • Rutherford - 1911
  • Fired alpha particles at thin metal sheet.
  • Expected them to go straight through, but some deflected.
slide23
II. Discoveries of atoms
  • J.J. Thomson – 1890s
  • Robert Millikan - 1909
  • Rutherford - 1911
  • Fired alpha particles at thin metal sheet.
  • Expected them to go straight through, but some deflected.
  • This led to nuclear model.
slide25
II. Discoveries of atoms
  • The atom
  • The electron was discovered first
slide26
II. Discoveries of atoms
  • The atom
  • The electron was discovered first
  • The proton was described by Rutherford
slide27
II. Discoveries of atoms
  • The atom
  • The electron was discovered first
  • The proton was described by Rutherford
  • The neutron was described by Chadwick
slide28
III. Representing Atoms

What makes a carbon atom different from a nitrogen atom?

slide29
III. Representing Atoms
  • The atomic number
slide30
III. Representing Atoms
  • The atomic number
  • The number of protons
slide31
III. Representing Atoms
  • The atomic number
  • The number of protons
  • Written on the periodic table.
slide32
III. Representing Atoms
  • The atomic number
  • The number of protons
  • Written on the periodic table.
  • This will equal the number of electrons, too.
slide33
III. Representing Atoms
  • The atomic number
  • The mass number
slide34
III. Representing Atoms
  • The atomic number
  • The mass number
  • The number of protons + neutrons
slide35
III. Representing Atoms
  • The atomic number
  • The mass number
  • The number of protons + neutrons
  • Always a whole number
slide36
III. Representing Atoms
  • The atomic number
  • The mass number
  • Isotopes
slide37
III. Representing Atoms
  • The atomic number
  • The mass number
  • Isotopes
  • Atoms with the same number of protons, different number of neutrons
slide38
III. Representing Atoms
  • The atomic number
  • The mass number
  • Isotopes
  • Atoms with the same number of protons, different number of neutrons
  • Isotopes have same properties, but different masses
slide39
III. Representing Atoms
  • The atomic number
  • The mass number
  • Isotopes
  • Notation
slide41
Nuclide Symbol Notation

Element symbol

Cl

37

17

slide42
Nuclide Symbol Notation

Cl

37

17

Atomic number

slide43
Nuclide Symbol Notation

Mass number

Cl

37

17

slide44
Self Check – Ex. 1

Write the nuclide symbols for elements with these particles:

Nuclide #1

22 protons

24 neutrons

Nuclide #2

22 protons

26 neutrons

slide45
Self Check – Ex. 2

How many protons, neutrons, and electrons are in this element?

95

Mo

42

slide46
Self Check – Ex. 3

How many protons, neutrons, and electrons are in this element?

40

K

slide48
IV. Mass of atoms
  • Measured in amu
slide49
IV. Mass of atoms
  • Measured in amu
  • Protons and neutrons both weigh about 1 amu (neutrons are a bit more)
slide50
IV. Mass of atoms
  • Measured in amu
  • Protons and neutrons both weigh about 1 amu (neutrons are a bit more)
  • The amu is defined as 1/12 the mass of carbon-12
slide52
V. Atomic Mass
  • A weighted average of all the isotopes for a given element
slide53
An analogy

The older pennies have a mass of 3.0 g while the newer pennies have mass of 2.5 g. What is the average mass of these pennies?

slide54
An analogy

The older pennies have a mass of 3.0 g while the newer pennies have mass of 2.5 g. What is the average mass of these pennies?

5

older

5

newer

slide55
An analogy

What is the average mass of this sample? There are 4 older pennies (3.0 g) while there are 10 newer pennies have mass of 2.5 g.

10

newer

4 older

slide56
An analogy

The older pennies have a mass of 3.0 g while the newer pennies have mass of 2.5 g. What is the average mass of these pennies?

older

newer

slide57
V. Atomic Mass
  • A weighted average of all the isotopes for a given element
  • Formula
slide58
Atomic Mass

% Isotope #1 x Mass of isotope #1

+

% Isotope #2 x Mass of isotope #2

+

% Isotope #3 x Mass of isotope #3

+

all other isotopes

=

Atomic mass

slide59
Self Check – Ex. 4

Use the following to find the atomic mass for chlorine.

Chlorine-35

75.53 %

34.969 amu

Chlorine-37

24.47 %

36.966 amu

slide61
VI. Radioactive Decay
  • Some atoms spontaneously emit radiation
slide62
VI. Radioactive Decay
  • Some atoms spontaneously emit radiation
  • Atoms change their identities in the process
slide63
VI. Radioactive Decay
  • Some atoms spontaneously emit radiation
  • Atoms change their identities in the process
  • Atoms undergo radioactive decay because their nuclei are unstable
slide66
VII. Types of Radiation
  • Alpha radiation
  • Make unstable heavy nuclei lighter
slide67
VII. Types of Radiation
  • Alpha radiation
  • Make unstable heavy nuclei lighter
  • This radiation is attracted to negative electric fields
slide68
VII. Types of Radiation
  • Alpha radiation
  • Make unstable heavy nuclei lighter
  • This radiation is attracted to negative electric fields
  • Comprised of alpha particles
slide69
Alpha Particles

2 protons & 2 neutrons

Made of:

Charge:

Mass:

Symbol:

slide70
Alpha Particles

2 protons & 2 neutrons

Made of:

Charge:

2 +

Mass:

Symbol:

slide71
Alpha Particles

2 protons & 2 neutrons

Made of:

Charge:

2 +

Mass:

4 amu

Symbol:

slide72
Alpha Particles

2 protons & 2 neutrons

Made of:

Charge:

2 +

Mass:

4 amu

4

4

Symbol:

He

or

α

2

2

slide74
VII. Types of Radiation
  • Beta radiation
  • Increases the proton to neutron ratio
slide75
VII. Types of Radiation
  • Beta radiation
  • Increases the proton to neutron ratio
  • Radiation is attracted to positive electric field
slide76
VII. Types of Radiation
  • Beta radiation
  • Increases the proton to neutron ratio
  • Radiation is attracted to positive electric field
  • Comprised of beta particles
slide77
Beta Particles

An electron from the nucleus

Made of:

Charge:

Mass:

Symbol:

slide78
Beta Particles

An electron from the nucleus

Made of:

Charge:

1 -

Mass:

Symbol:

slide79
Beta Particles

An electron from the nucleus

Made of:

Charge:

1 -

Mass:

1/1840 amu

Symbol:

slide80
Beta Particles

An electron from the nucleus

Made of:

Charge:

1 -

Mass:

1/1840 amu

0

0

Symbol:

e-

or

β

-1

-1

slide82
VII. Types of Radiation
  • Gamma radiation
  • These accompany alpha and beta radiation
slide83
VII. Types of Radiation
  • Gamma radiation
  • These accompany alpha and beta radiation
  • Not deflected by electric field
slide84
VII. Types of Radiation
  • Gamma radiation
  • These accompany alpha and beta radiation
  • Not deflected by electric field
  • Gamma rays are high energy radiation
slide85
Gamma Particles

Energy (not matter)

Made of:

Charge:

none

Mass:

none

Symbol:

γ

0

0

slide87
VIII. Penetrating Ability
  • Alpha radiation penetrates the .
slide88
VIII. Penetrating Ability
  • Alpha radiation penetrates the least.
  • Gamma radiation penetrates the .
slide89
VIII. Penetrating Ability
  • Alpha radiation penetrates the least.
  • Gamma radiation penetrates the most.
slide91
IX. Writing Equations
  • Atomic numbers and mass numbers are conserved
slide92
IX. Writing Equations
  • Atomic numbers and mass numbers are conserved
  • Examples
slide93
Self Check – Ex. 5

Complete the following nuclear equation.

40

40

K Ca + ?

19

20

slide94
Self Check – Ex. 6

Complete the following nuclear equation.

239

4

Pu ? + α

94

2

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