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3.1/3.2 Review Name________________________________

Chemists & Models of the Atom Period_______Date_____________________

Part I: Chemists in History - Write the name of the chemist who proposed each of the ideas listed below. Some names may be used more than once.

Democritus Lavoisier Proust DaltonFranklin Thomson Becquerel Marie & Pierre Curie Rutherford Bohr Moseley Modern Model

_____________________ 1. Stated that matter is neither created nor destroyed in chemical reactions.

_____________________ 2. Stated that a given compound always has the same relative number and kinds of atoms.

_____________________ 3. Discovered radioactivity while working with a sample of Uranium.

_____________________ 4. Determined that a cathode ray is made of electrons.

_____________________ 5. Isolated two new elements, radium and polonium.

_____________________ 6. Understood the atom to have a central nucleus with electrons orbiting around in fixed paths like planets around the sun.

_____________________ 7. Stated that all atoms of a given element are identical, but they differ from those of other elements.

_____________________ 8. Stated that all matter is composed of tiny, indivisible particles called atoms.

_____________________ 9. Found that there are three types of natural radiation.

_____________________ 10. First person to suggest that the atom is related to electricity.

_____________________ 11. Uses Quantum Mechanics and states that the electron may be found in a probability region.

_____________________ 12. Determined that each atom has it own atomic number (number of protons.)

_____________________ 13. Used Gold Foil to determine that all the positive matter (protons) is concentrated into a very small, very dense nucleus and that most of the atom is empty space.

Part II: Experiments about the Atom – Fill in the blanks with the appropriate word. Each word or number will only be used once.

0 anode beta cathode+2 electrons empty space exposed3 gamma large massno negative positively proton (nucleus)

14. The negatively charged electrode of a cathode ray tube is the ___________________, the positively

charged electrode is called the ______________________.

15. In Thomson’s experiment, the cathode ray is deflected by the magnet, this indicated that the ray had

____________________. When the electrically charged plates were turned on, the cathode ray was

deflected toward the positive plate, this indicated that the beam had a ____________________ charge.

16. Therefore a cathode ray is made of a beam of ____________________.

17. Becquerel discovered radiation because a sample of uranium ore __________________ a piece of photographic film.

18. Rutherford used a radioactive sample and determined that natural radiation has ______ components:

alpha particles which have a _______ charge and a relatively _______________ mass,

________________ particles which have a negative charge and a mass of ______ and

______________ rays which are neutral and have ________ mass.

19. Rutherford used alpha particles in his Gold Foil experiment. Because the alpha particles are relatively

large and positive the fact that most of them proceeded straight through the foil proved that the atom

is mostly _____________________________. Some of the positive alpha particles deflected directly

back toward the source which indicated that the nucleus was _______________________ charged

Thus, Rutherford is credited with discovering the ___________________.

20. Draw a simple sketch of each chemist’s model of the atom. Indicate charge where needed.Dalton Thomson Rutherford Bohr Modern Model

3.3 Practice

Protons, Neutrons and Electrons

21. How many protons and electrons are in a vanadium atom?

22. How many protons and electrons are present in a nitrogen atom?

23. How many protons and electrons are present in an argon atom?

24. How many protons and electrons are present in a potassium atom?

25. How many protons and electrons are present in a platinum atom?

26. What is the name of the element that has atoms that contain 5 protons?





31. Write the chemical symbol for the ion with 12 protons and 10 electrons.





36. How many protons, neutrons and electrons are present in the ion?






42. Write the isotopic symbol for the ion with 84 protons, 125 neutrons and 80 electrons.




46. Atomic Structure

Isotopic Name

Isotopic Symbol Atomic # Mass # # of

protons# of

neutrons#

electrons

1 2 4

2 12 12

3 Zinc - 65

4 35 45

5

6 Uranium – 238

7 11 12

8 47 36

9 197 79

10 108 47

11 Titanium-48

47. Atomic Structure Practice Chart

Isotopic Name

Isotopic Symbol

# of protons

# of electrons

# of neutrons Atomic # Mass #

1 14 15

2 136 86

3 36 84

4 gold – 197

5 20 21

6 17 35

48. Complete the following table for the following ions:

Complete Isotopic Symbol

Atomic Number

Mass Number # of p+ # of e- # of n° Charge

Cationor

Anion

cation

8 15 -2

24 23 27

25 10 13

26 13 10

32 40 +4

83 86 126

Formation of Ions

49. Calculate the charges on the following ions, and indicate whether the ion is a cation or anion.

Ion Number of Protons

Number of Electrons

Charge Cation or Anion?

Magnesium 12 10

Fluoride 9 10

Sulfide 16 18

Gold 79 76

50. Consult the periodic table and give the symbol for the ions that have:

a. 28 protons and 26 electrons ___________

b. 34 protons and 36 electrons ___________

51. Complete the following table for ions:

Symbol for Ion

Atomic Number

Mass Number

Protons Neutrons Electrons Charge

Cl-1 37

Mg+2 24

K+1 39O-2 16

Al+3 30

P-3 31

52. Write the symbol including the mass number, atomic number and charge for the ions containing the following numbers of protons, neutrons, and electrons.

A. 16 p+, 16 n , 18 e- D. 1 p+ , 0 n, 0 e-

B. 35 p+, 45n , 36 e- E. 13 p+, 14 n , 10 e-

C. 20 p+, 20 n , 18 e- F. 11 p+, 12 n , 10 e-

53. Fill in the following table about the formation of ions.

Ion Symbol Charge Atomic # # of p+ # of e- Ion formed by

Potassium Loss of 1 e-

Ba+2

+4 50

-1 53

33 36

16 Gain of 2 e-

+3 28

Isotopes and Average Atomic Mass and Ions

Elements come in a variety of isotopes, meaning they are made up of atoms with the same atomic number, but different atomic masses. These atoms differ in the number of neutrons. The average atomic mass if the weighted average of all the isotopes of an element.

Example: A sample of cesium is 75% , 20.% , and 5% . What is the average atomic mass?

Answer: .75 x 133 = 99.75.20 x 132 = 26.4.05 x 134 = 6.7 +

Total = 132.85 amu = average atomic mass

Determine the average atomic mass of the following mixtures of isotopes. _________________________________________________________________________________

54. 80.% , 17% , 3%

55. 50.% , 50.%

56. 15% , 85%

57. 99% , 0.8% , 0.2%

58. 95% , 3% , 2%

59. 98% , 2%

______________________________________________________________________60. Uranium has 3 isotopes with the following relative abundances: Uranium-234 (0.0058%), U-235 (0.71%), and U-238 (99.23%). Calculate the average atomic mass of uranium:

61. Fill in the blanks in the following table using the periodic table when necessary. If not otherwise noted,

assume the elements to be neutral atoms.

Symbol Protons Electrons Neutrons Mass Number Atomic Number

A

B 59 141

C 60 44

D 24 45

E

F 22 28

62. Write the hyphen notation for each of the six isotopes listed above:

A. _____________________ B. _____________________ C. ____________________

D. _____________________ E. _____________________ F. ____________________

63. Indicate the charge (+1, -1, etc) on the ions that are formed in the following situations. Record the

resultant ion as a cation or anion.Charge Cation/Anion

a. Lithium loses 1 electron _____________ _______________

b. Oxygen gains 2 electrons _____________ _______________

c. Magnesium loses 2 electrons _____________ _______________

d. Nitrogen gains 3 electrons _____________ _______________

HISTORY OF THE ATOM REVIEW

64. _______________ was the ancient philosopher who first proposed the existence of atoms.

65. _______________ showed that matter is neither ___________________ nor _________________ in chemical reactions, and is known as the “Father of Chemistry.”

66. _______________ created the first atomic theory. He thought that all atoms of an element are identical, and that atoms of different elements are different from each other. His model of the atom is represented below.

67. The Law of ___________________ _____________________ states that compounds always have

the same elements in the same ratio by mass.

68. _____________________ discovered the electron using a cathode ray tube. Current flows from the

___________ to the ___________. Because the beam was deflected toward a positively charged plate

(Letter C), the beam must have a ___________ charge. Because the beam was also affected by a

magnet (Letter A), cathode rays also have _______. This led to the __________ ____________ model

of the atom, shown below.

69. _______________________ is credited with discovering the nucleus of the atom, during his famous

__________________________experiment. He used a radioactive source to beam positively charged

_________ _________________ toward a very thin film of gold foil. Most of the particles

_______________________________________, but some were ____________ at various angles. From

this he concluded that most of the atom is ___________________, with a small _______________

charged nucleus in the center, and the electrons somewhere outside. His experimental results and newer

model of the atom are shown on the next page.

70. _____________ proposed that electrons moved in fixed orbits around the nucleus, like planets around

the sun - the ________ ___________ model. (Left below)

71. In the modern model of the atom, the nucleus contains ___________ and ___________, with the

______________ outside in a cloud. (Right below)

72. ___________________ discovered radioactivity when pitchblende, an ore containing ______________,

exposed photographic film. Rutherford later showed three types of radiation, by exposing a beam of

radiation to electrical plates. An Alpha particle is the same as a ___________ ___________, has a

___________ charge, so is attracted to the ____________ plate. Write the symbol for an alpha particle

___________. A Beta particle is the same as an _____________, has a ___________ charge, and is

attracted to the ________ plate. The electron has less mass, so is deflected more. Gamma rays are pure

_________, have _____ charge, and thus are __________ by the electrical plates. Label the alpha

and beta particles and gamma rays in the drawing below.

II. PROBLEMS:

73. Summarize the information you have gained about subatomic particles in the table below:

Particle Symbol Relative Mass (AMU) Electrical Charge Location in the

Atom

electron

neutron

proton

74. Why are atoms electrically neutral?______________________________________________________

75. Define the following terms:

A. atomic number

B. mass number

C. isotope

_

D. isotopic symbol

E. average atomic mass

F. ion

G. charge

76. A. A nitrogen atom has 7 protons and 7 neutrons. Calculate:

1. the atomic number ______ 2. the mass number ______

B. A phosphorus atom has 15 protons, 18 electrons, and 16 neutrons. Calculate:

1. the atomic number ______ 2. the mass number ______ 3. the charge

77. If a sulfur atom is neutral in charge and contains 16 protons in the nucleus, how many electrons are present outside the nucleus? ______

78. Write the isotopic symbol for a lithium atom with 3 protons and 4 neutrons: _________

79. Which of the following are isotopes of each other? Why?______________________________________

A) B) -2 C)

80. An isotope of silver has 47 protons, 46 electrons and 60 neutrons.

A) What is the atomic number? ______

B) What is the mass number? ______

C) How many electrons are present? ______

D) Write the complete isotopic symbol for the element:

81. Circle the one in each of the pairs of elements has the most neutrons.

A) or B) or

82. In a nuclear reactor, an isotope of uranium, called U-235, is used. It has 92 protons and a mass number of 235.A) What is the atomic number? ______

B) How many electrons are present? ______

C) How many neutrons are present? ______

D) Write the complete isotopic symbol for the element:

83. Complete the following table for each of the isotopes listed:

-2 +1

What is the atomic number?

What is the mass number?

How many protons?

How many neutrons?

How many electrons?

84. For each of the following pairs of elements, decide whether or not the pairs of elements are isotopes or completely different elements.

A) Element A has 22 protons and 24 neutrons. Element B has 22 protons and 25 neutrons. _______

B) Element C has 29 protons and 34 neutrons. Element D has 30 protons and 34 neutrons. ________

C) Element E has 24 protons and a mass of 50. Element F has the isotopic symbol . __________

E) Element G has an atomic number of 28 and a mass of 64. ______________________________

Element H has 30 protons and the symbol .

F) Element I is neutral and has 78 electrons and 117 neutrons. _______________________________

Element J has the isotopic symbol .

85. A. An atom contains 15 protons, 16 neutrons and 15 electrons. Write the isotopic symbol: _________

B. Write the isotopic symbol for a possible isotope of this atom: ___________

C. If the atom gains three electrons, write the isotopic symbol for the ion: ___________

86. Complete the following table:Isotope Name Symbol Atomic

NumberMass

Number Protons Neutrons Electrons Charge

Sodium-23 0

+2

27 32 +2

15 7 10

32 72 0

13 10 +3

19 20 18

51 23 0

87. With the help of the periodic table, tell the number of protons, neutrons and electrons in each of the following isotopes:

A. carbon-14 p: _______ n:_______ e: _______

B. cobalt-60 p: _______ n:_______ e: _______

C. bromine-81 p: _______ n:_______ e: _______

D. strontium-90 p: _______ n:_______ e: _______

E. +3 p: _______ n:_______ e: _______

F. p: _______ n:_______ e: _______

G. +2 p: _______ n:_______ e: _______

H. p: _______ n:_______ e: _______

88. Write isotopic symbols for neutral atoms with:

A. 9 p+ and 10 no __________ C. 31 p+ and 39 no __________

B. 25 p+ and 30 no ___________ D. 1 p+ and 0 no __________

89. Which of the following atoms are isotopes?

A. B. C. D. E. F. 90. Consult the periodic table and identify each of the elements listed in #89 above.

A. _______________ B. __________________ C. ___________________

D. _______________ E. __________________ F. ___________________

91. A certain isotope of cobalt is five times as heavy as . What is the mass number of this isotope? _____

92. Choose the best answer from the choices given and circle its number.A. Neutral atoms have…

1) more negative charge than positive charge.2) more positive charge than negative charge.3) equal amounts of positive and negative charge.4) variable charge.

B. The particle having the greatest actual mass is the…1) electron 2) neutron 3) neutrino 4) proton

C. A particle that is present in every atom is the…1) positron 2) proton 3) neutron 4) neutrino

D. The charge on the nucleus of an atom is due to…1) neutrons 2) positrons 3) protons 4) electrons

E. All atoms of a given element have the same…1) number of nucleons 3) number of neutrons2) number of protons 4) mass number

F. Which atomic particle would NOT be deflected by an electrical field?1) neutron 2) alpha particle 3) beta particle 4) proton

G. The neutrons of an atom…1) revolve around the nucleus 3) are positively charged2) contribute to atomic mass 4) determine atomic number

H. The subatomic particles which have equal but opposite charges are…1) proton and electron 3) nucleus and neutron2) proton and neutron 4) electron and neutron

I. Which particle has the least mass?1) proton 2) neutron 3) alpha particle 4) electron

J. A pure substance whose atoms all have the same atomic number is a(n)…1) compound 2) element 3) radical 4) mixture

K. Isotopes of an element have the same…

1) make-up of the nucleus 3) number of protons2) number of atoms 4) number of neutrons

L. An atom containing 9 protons, 10 neutrons and 9 electrons has a mass number of…1) 9 2) 18 3) 19 4) 28

M. As the number of neutrons in the nucleus of an atom increases, the atomic number of the element…1) decreases 2) increases 3) remains the same

N. As the atomic numbers of the elements increases, the number of protons in the nucleus1) decreases 2) increases 3) remains the same

O. The symbols , , and show that the three kinds of hydrogen atoms have…1) the same atomic mass 3) the same number of protons2) different atomic numbers 4) the same number of neutrons

P. The number of neutrons in the nucleus of a atom is…1) 1 2) 2 3) 3 4) 4

Q. As the atomic mass of chlorine isotopes increases, the number of protons…1) decreases 2) increases 3) remains the same

R. The number of protons in the nucleus of an oxygen atom is…1) 8 2) 9 3) 20 4) 17

S. The number of neutrons in the nucleus of is…1) 17 2) 18 3) 20 4) 37

T. The atom whose nucleus contains the largest number of neutrons is…

1) 2) 3) 4)

U. The symbol which shows phosphorus with a mass number of 31 is…

1) 2) 3) 4)

V. What is the correct symbol for an element containing 6 protons and 8 neutrons…

1) 2) 3) 4)

W. If an atom gains an electron, it becomes…1) a cation 2) an anion 3) neutral

X. A negative two (-2) charge indicates that the atom…1) gained two electrons 3) gained two protons2) lost two electrons 4) lost two protons

Average Atomic Mass: Use the concept of isotopes to explain why the atomic masses of elements are not whole numbers. ___________________________________________________________________

Example: Use the following information to determine the atomic mass of chlorine. Two isotopes are known: chlorine-35 (mass = 35.0 amu) and chlorine-37 (mass = 37.0 amu). The relative abundances are 75.4% and 24.6%, respectively.Solution: Recall that the text defines atomic mass as the weighted average of the masses of the isotopes of that element. To solve the problem:

Contribution of masses by each isotope = mass of isotope x relative abundance = = 35.0 amu x 0.754 = 26.4 amu = 37.0 amu x 0.246 = 9.10 amu

The sum of the individual isotope mass contributions will equal the atomic mass. 26.4 amu + 9.10 amu = 35.5 amu

Problems:A. Two isotopes are known: carbon-12 (mass = 12.00 amu) and carbon-13 (mass = 13.00 amu). Their

relative abundances are 98.9% and 1.10% respectively. Determine the atomic mass of carbon.

B. Given the relative abundance of the following naturally occurring isotopes of oxygen, calculate the average atomic mass of oxygen:

99.76% oxygen-16 0.037% oxygen-17 0.204% oxygen-18

C. Determine the atomic mass of an element which has 2 isotopes with numbers of 6 (mass = 6.02) and 7 (mass = 7.02). The relative abundances are 7.42% and 92.6%, respectively.

D. Calculate the average atomic mass of an element from isotope data. Element Y has 2 isotopes.One has a mass number of 10, and a relative abundance of 20.%. The other isotope has a mass number of 11 and a relative abundance of 80.%.

Atomic Structure Review Sheet

Atoms of each element are ______________________ from the atoms of all other elements.

Dalton theorized that atoms are indivisible, but the discovery of _________________ particles changed

his theory. We now know that atoms are made up of electrons, which have a _______________________

charge; __________________, which have a positive charge; and ___________________, which are

neutral. The latter two particles are found in the _____________________ of the atom.

It was ______________________ who discovered the nucleus of the atom. The nucleus has a

____________________ charge and it occupies a very small volume of the atom. In contrast, the

negatively charged __________________ occupy most of the volume of the atom.

The number of _________________________ in the nucleus of the atom is the atomic

____________________ of that element. Because atoms are electrically neutral, the number of protons

and _____________________ in an atom are equal. The sum of the __________________ and neutrons

is the mass number. Atoms of the same element are identical in some respects, but they can differ in the

number of ________________ in the nucleus. Atoms that have the same number of protons but have

different mass numbers are called _______________________.

The ______________________ of an element is the weighted average of the masses of the

isotopes of that element. Two isotopes of sulfur are and . An atom of the sulfur-32 isotope

contains _______________ protons and ______________ neutrons. The sulfur-34 isotope has

_______________ protons and ______________ neutrons.

Each of the three known isotopes of hydrogen has ________________ proton(s) in the nucleus.

The most common hydrogen isotope has ________________ neutrons. It has a mass number of

________________ amu and is called hydrogen-1.

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