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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