1. Chemistry 4.1
Chapter 4
Section 1

2. Early Models of the Atom
4.1
Early Models of the Atom
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.

3. Early Models of the Atom
4.1
Early Models of the Atom
Democritus’s Atomic Philosophy
How did Democritus describe atoms?
Democritus

4. Early Models of the Atom
4.1
Early Models of the Atom
Democritus believed that atoms were indivisible and indestructible.
Democritus’s ideas were limited because they didn’t explain chemical behavior and they lacked experimental support.

5. Early Models of the Atom
4.1
Early Models of the Atom
Dalton’s Atomic Theory
How did John Dalton further Democritus’s ideas on atoms?

6. Early Models of the Atom
4.1
Early Models of the Atom
By using experimental methods, Dalton transformed Democritus’s ideas on atoms into a scientific theory.
The result was Dalton’s atomic theory.

7. Early Models of the Atom
4.1
Early Models of the Atom
All elements are composed of tiny indivisible particles called atoms.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

8. Early Models of the Atom
4.1
Early Models of the Atom
Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

9. Early Models of the Atom
4.1
Early Models of the Atom
Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

10. Early Models of the Atom
4.1
Early Models of the Atom
Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element are never changed into atoms of another element in a chemical reaction.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?
Scientists used a scanning tunneling microscope to generate this image of iron atoms, shown in blue. The radius of this circle of atoms is just 7.13 × 10-9 m.

11. 4.1
Sizing up the Atom
Sizing up the Atom
What instruments are used to observe individual atoms?

12. 4.1
Sizing up the Atom
Despite their small size, individual atoms are observable with instruments such as scanning tunneling microscopes.

13. 4.1 Section Quiz
4.1.

14. 4.1 Section Quiz
1. The ancient Greek philosopher credited with suggesting all matter is made of indivisible atoms is
Plato.
Aristotle.
Democritus.
Socrates.
ANS: C PTS: 1 REF: p. 101 OBJ: 4.1.1

15. 2. Dalton's atomic theory improved earlier atomic theory by
4.1 Section Quiz
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.
ANS: C PTS: 1 REF: p. 102 OBJ: 4.1.2

16. 3. Individual atoms are observable with the naked eye.
4.1 Section Quiz
3. Individual atoms are observable with
the naked eye.
a magnifying glass.
a light microscope.
a scanning tunneling microscope.
ANS: D PTS: 1 REF: p. 103 OBJ: 4.1.3

17. Chemistry 4.2
Chapter 4
Section 2

18. Subatomic Particles What are three kinds of subatomic particles? 4.2

19. 4.2
Subatomic Particles
Three kinds of subatomic particles are electrons, protons, and neutrons.

20. 4.2
Subatomic Particles
Electrons
In 1897, the English physicist J. J. Thomson (1856–1940) discovered the electron. Electrons are negatively charged subatomic particles.

21. 4.2
Subatomic Particles
Thomson performed experiments that involved passing electric current through gases at low pressure. The result was a glowing beam, or cathode ray, that traveled from the cathode to the anode.

22. Cathode Ray Tube 4.2 Subatomic Particles
In a cathode-ray tube, electrons travel as a ray from the cathode (-) to the anode (+). A television tube is a specialized type of cathode-ray tube.

23. A cathode ray is deflected by a magnet.
4.2
Subatomic Particles
A cathode ray is deflected by a magnet.
Thomson examined two ways that a cathode ray can be deflected: a) by using a magnet, and b) by using electrically charged plates. Inferring If a cathode ray is attracted to a positively charged plate, what can you infer about the charge of the particles that make up the cathode ray?

24. A cathode ray is deflected by electrically charged plates.
4.2
Subatomic Particles
A cathode ray is deflected by electrically charged plates.
In a cathode-ray tube, electrons travel as a ray from the cathode (-) to the anode (+). A television tube is a specialized type of cathode-ray tube.

25. 4.2
Subatomic Particles
Thomson concluded that a cathode ray is a stream of electrons. Electrons are parts of the atoms of all elements.
Thompson built upon the foundation of George Stoney, who proposed the negative particle and named it the electron.

26. Thompson built upon the foundations of:
4.2
Subatomic Particles
Thompson built upon the foundations of:
George Stoney, who proposed the negative particle and named it the electron.
Julius Plucker: who developed the CRT
Sir William Crooks: proposed that there were particles in the CT beam.

27. Such positively charged subatomic particles are called protons.
4.2
Subatomic Particles
Protons and Neutrons
In 1886, Eugen Goldstein (1850–1930) observed a cathode-ray tube and found rays traveling in the direction opposite to that of the cathode rays. He concluded that they were composed of positive particles.
Such positively charged subatomic particles are called protons.

28. 4.2
Subatomic Particles
In 1932, the English physicist James Chadwick (1891–1974) confirmed the existence of yet another subatomic particle: the neutron.
Neutrons are subatomic particles with no charge but with a mass nearly equal to that of a proton.

29. 4.2
Subatomic Particles
Table 4.1 summarizes the properties of electrons, protons, and neutrons.

30. 4.2
The Atomic Nucleus
The Atomic Nucleus
How can you describe the structure of the nuclear atom?

31. 4.2
The Atomic Nucleus
J.J. Thompson and others supposed the atom was filled with positively charged material and the electrons were evenly distributed throughout.
This model of the atom turned out to be short- lived, however, due to the work of Ernest Rutherford (1871–1937).

32. Ernest Rutherford’s Portrait
4.2
The Atomic Nucleus
Ernest Rutherford’s Portrait
Born in New Zealand, Ernest Rutherford was awarded the Nobel Prize for Chemistry in His portrait appears on the New Zealand $100 bill.

33. Rutherford’s Gold-Foil Experiment
4.2
The Atomic Nucleus
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.

34. Rutherford’s Gold-Foil Experiment
4.2
The Atomic Nucleus
Rutherford’s Gold-Foil Experiment
Rutherford’s gold-foil experiment yielded evidence of the atomic nucleus. a) Rutherford and his coworkers aimed a beam of alpha particles at a sheet of gold foil surrounded by a fluorescent screen. Most of the particles passed through the foil with no deflection at all. A few particles were greatly deflected. b) Rutherford concluded that most of the alpha particles pass through the gold foil because the atom is mostly empty space. The mass and positive charge are concentrated in a small region of the atom. Rutherford called this region the nucleus. Particles that approach the nucleus closely are greatly deflected.

35. Alpha particles scatter from the gold foil.
4.2
The Atomic Nucleus
Alpha particles scatter from the gold foil.
Rutherford’s gold-foil experiment yielded evidence of the atomic nucleus. a) Rutherford and his coworkers aimed a beam of alpha particles at a sheet of gold foil surrounded by a fluorescent screen. Most of the particles passed through the foil with no deflection at all. A few particles were greatly deflected. b) Rutherford concluded that most of the alpha particles pass through the gold foil because the atom is mostly empty space. The mass and positive charge are concentrated in a small region of the atom. Rutherford called this region the nucleus. Particles that approach the nucleus closely are greatly deflected.

36. The Rutherford Atomic Model
4.2
The Atomic Nucleus
The Rutherford Atomic Model
Rutherford concluded that the atom is mostly empty space. All the positive charge and almost all of the mass are concentrated in a small region called the nucleus.
The nucleus is the tiny central core of an atom and is composed of protons and neutrons.

37. Democritus – Greek – Atmos (400 B.C.) Dalton – Atomic Theory (1803)
4.2
Scientists
Democritus – Greek – Atmos (400 B.C.)
Dalton – Atomic Theory (1803)
Plucker – CRT (1860)
Stoney – proposed electron (1874)
Crooks – particles in CRT (1879)
J. J. Thompson – CRT, electrons, Plum Pudding Model, charge/mass ratio (1897)

38. Rutherford – discovered nucleus (1911)
4.2
Scientists
Rutherford – discovered nucleus (1911)
Geiger and Marsden did the gold-foil experiment
Bohr Model – proposed energy levels, orbit or planetary model (1913)
Robert Millikan – Oil-drop experiment, mass of electron (1916)
De Broglie – wave/particle duality (1923)
Schrodinger – Electron cloud model (1926)
Chadwick – confirmed Neutron (1932)

39. 4.2
The Atomic Nucleus
In the nuclear atom, the protons and neutrons are located in the nucleus. The electrons are distributed around the nucleus and occupy almost all the volume of the atom.

40. 4.2 Section Quiz
4.2.

41. 1. Which of the following is NOT an example of a subatomic particle?
4.2 Section Quiz
1. Which of the following is NOT an example of a subatomic particle?
proton
molecule
electron
neutron
ANS: B PTS: 1 REF: p. 104 OBJ: 4.2.1

42. 2. The nucleus of an atom consists of electrons only. protons only.
4.2 Section Quiz
2. The nucleus of an atom consists of
electrons only.
protons only.
protons and neutrons.
electrons and neutrons.
ANS: C PTS: 1 REF: p. 107 OBJ: 4.2.2

43. 3. Most of the volume of the atom is occupied by the
4.2 Section Quiz
3. Most of the volume of the atom is occupied by the
electrons.
neutrons.
protons and neutrons.
protons.
ANS: A PTS: 1 REF: p. 108 OBJ: 4.2.2

44. Chemistry 4.3
Chapter 4
Section 3

45. Atomic Number What makes one element different from another? 4.3

46. 4.3
Atomic Number
Elements are different because they contain different numbers of protons.
The atomic number of an element is the number of protons in the nucleus of an atom of that element.

47. 4.3
Atomic Number

49. for Conceptual Problem 4.1
Problem Solving 4.15 Solve Problem 15 with the help of an interactive guided tutorial.

50. Mass Number How do you find the number of neutrons in an atom? 4.3

51. 4.3
Mass Number
The total number of protons and neutrons in an atom is called the mass number.
The number of neutrons in an atom is the difference between the mass number and atomic number.

52. Au is the chemical symbol for gold.
4.3
Mass Number
Au is the chemical symbol for gold.
Au is the chemical symbol for gold. Applying Concepts How many electrons does a gold atom have?

53. 4.1

54. 4.1

55. 4.1

56. for Sample Problem 4.1
Problem Solving 4.17 Solve Problem 17 with the help of an interactive guided tutorial.

57. 4.3
Isotopes
Isotopes
How do isotopes of an element differ?

58. 4.3
Isotopes
Isotopes are atoms that have the same number of protons but different numbers of neutrons.
Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.

59. 4.3
Isotopes
Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons.
Neon-20, neon-21, and neon-22 are three isotopes of neon, a gaseous element used in lighted signs. Comparing and Contrasting How are these isotopes different? How are they similar?

61. Atomic Mass How do you calculate the atomic mass of an element? 4.3

62. 4.3
Atomic Mass
It is useful to to compare the relative masses of atoms to a standard reference isotope. Carbon- 12 is the standard reference isotope. Cabon-12 has a mass of exactly 12 atomic mass units.
An atomic mass unit (amu) is defined as one twelfth of the mass of a carbon-12 atom.

63. Some Elements and Their Isotopes
4.3
Atomic Mass
Some Elements and Their Isotopes

64. 4.3
Atomic Mass
The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element.
A weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature.

65. Weighted Average Mass of a Chlorine Atom
4.3
Atomic Mass
Weighted Average Mass of a Chlorine Atom
Chlorine is a reactive element used to disinfect swimming pools. Chlorine occurs as two isotopes: chlorine-35 and chlorine-37. Because there is more chlorine-35 than chlorine-37, the atomic mass of chlorine, amu, is closer to 35 than to 37. Evaluating How does a weighted average differ from an arithmetic mean?

67. for Conceptual Problem 4.3
Problem Solving 4.21 Solve Problem 21 with the help of an interactive guided tutorial.

68. 4.3
Atomic Mass
To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products.

69. For example, carbon has two stable isotopes:
4.3
Atomic Mass
For example, carbon has two stable isotopes:
Carbon-12, which has a natural abundance of %, and
Carbon-13, which has a natural abundance of 1.11%.

70. 4.2

71. 4.2

72. 4.2

73. 4.2

74. for Sample Problem 4.2
Problem Solving 4.24 Solve Problem 24 with the help of an interactive guided tutorial.

75. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
The Periodic Table—A Preview
Why is a periodic table useful?

76. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
A periodic table is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties.
A periodic table allows you to easily compare the properties of one element (or a group of elements) to another element (or group of elements).

77. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
The Periodic Table
Elements are arranged in the modern periodic table in order of atomic number. Interpreting Diagrams How many elements are in Period 2? In Group 2A?

78. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
Each horizontal row of the periodic table is called a period.
Within a given period, the properties of the elements vary as you move across it from element to element.

79. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
A Period

80. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
Each vertical column of the periodic table is called a group, or family.
Elements within a group have similar chemical and physical properties.

81. The Periodic Table—A Preview
4.3
The Periodic Table—A Preview
A Group or Family

82. 4.3 Section Quiz
4.3.

83. 1. Isotopes of an element have the same mass number.
4.3 Section Quiz
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.
ANS: C PTS: 1 REF: p. 112 OBJ: 4.3.1

84. 2. How many neutrons are in sulfur-33? 16 neutrons 33 neutrons
4.3 Section Quiz
2. How many neutrons are in sulfur-33?
16 neutrons
33 neutrons
17 neutrons
32.06 neutrons
ANS: C PTS: 1 REF: p. 111 OBJ: 4.3.2

85. 4.3 Section Quiz
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.
ANS: A PTS: 1 REF: p. 116 OBJ: 4.3.3

86. Concept Map

87. END OF SHOW