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Name: ______Period:______Unit 2: The Atom Day Page # Description IC/HW Due ? Date: Done? WebQuest: Atomic Theories and 0 X IC/HW Models

1 3 Atomic Models Summary Table IC

The Atom and Average Atomic 1 4-6 IC Mass Notes 2-A: Atomic Structure and 1 9-10 HW Day 2 Average Worksheet 2-V1: The Atom and Average 1 VISION HW Atomic Mass HW and Half-life 2 6-8 IC Notes 2-B: Radioactive Decay and Half 2 11-12 HW Day 3 Life Worksheet

2 13-16 Unit 2 Review HW

4 Unit 2 Quiz

Unit 2 1

Atomic Models Summary Table Name Characteristics Picture Electrons: (marble model) Protons: Neutrons: Other:

Thomson Electrons: (plum pudding model) Protons: Neutrons: Other:

Rutherford Electrons: (planetary model) Protons: Neutrons: Other:

Bohr Electrons: (quantum model) Protons: Neutrons: Other:

Important Scientists in the Atomic Theories and Models -atomos, initial idea of atom – Democritus - first atomic theory of matter, solid sphere model – John Dalton - discovery of the electron using the cathode ray tube experiment, plum pudding model – J. J. Thomson - discovery of the nucleus using the foil experiment, nuclear model – Ernest Rutherford - discovery of charge of electron using the oil drop experiment – Robert Millikan - energy levels, planetary model – Niels Bohr - periodic table arranged by atomic mass – Dmitri Mendeleev - periodic table arranged by atomic number – Henry Moseley - quantum nature of energy – Max Planck - uncertainty principle, quantum mechanical model – Werner Heisenberg - wave theory, quantum mechanical model – Louis de Broglie.

Unit 2 2

The Atom- Notes

- Atoms are the basic unit of ______and is

made up of ______particles

Atomic Subatomic Proton Neutron Electron Particles

Where is it?

Mass

Charge

Influence (What happens if you change it?)

 Atomic Number – the number of ______in an element

 Mass Number – the number of ______and ______in an element

– Atoms of an element with different number of ______, giving it

a different ______but the same ______.

 AMU - ______; used to describe the mass of subatomic particles

 Standard nuclear notation is used to represent each isotope in existence. 퐴 푍푋  Write the symbol for the atom that has an atomic number of 9 and a mass number of 19. How many protons, neutrons and electrons does this atom have?

Unit 2 3

How many protons, neutrons and electrons does this atom have? Isotope Protons Neutrons Electrons

Oxygen-16

Hydrogen-2

Carbon-13

Nitrogen-15

Average Atomic Mass- Notes

 The mass of each element is a ______of the in the element.  Example 1: has three stable isotopes. The following information is available for the three isotopes: Fractional Relative Relative Mass Isotope Mass (amu) Abundance (%) Abundance (amu)

Silicon-28 27.977 92.21

Silicon-29 28.976 4.70

Silicon-30 29.974 3.09

 Example 2: Element J has four stable isotopes. The following information is available for the four isotopes. Determine the average atomic mass and identity of element J. Isotope Mass (amu) Fractional Abundance (%) J-54 53.9396127 5.845 J-56 55.9349393 91.754 J-57 56.9353958 2.119 J-58 57.9332773 0.282

Unit 2 4

 Example 3: The two naturally occurring isotopes of are 35Cl with a mass of 34.9689 amu and 37Cl with a mass of 36.9659 amu. The atomic mass of elemental chlorine on earth is found to be 35.46 amu. Calculate the percent abundance of each of the two chlorine isotopes.

Average Atomic Mass Practice:

1. Find the average atomic mass for Li if 7.50 % of Li atoms are 6-Li with a mass of 6.01512 amu and 92.5% are 7-Li with a mass of 7.0160 amu

2. Find the average atomic mass for element M if 19.9% of M atoms have a mass of 10.0129 amu and 80.1% are 11.0093 amu. Determine the identity of element M.

3. has two stable isotopes: 151Eu with a mass of 150.9196 amu and153Eu with a mass of 152.9209. If elemental Europium is found to have a mass of 151.96 amu on earth, calculate the percent of each of the two isotopes.

Unit 2 5

Radioactive Decay Notes  The stability of a nucleus is dependent on the ratio of neutrons to protons (N:Z).  For light nuclei (atomic number of 20 and less), the N:Z ratio should be 1:1.  For heavy nuclei (above 20), the N:Z ratio should be 1.5:1.

Band of Stability  Atoms that lie either above or below the band of stability will undergo nuclear decay to achieve stability.  Atoms that lie ABOVE the band of stability have ______

______.

 Atoms that lie BELOW the band of stability have ______

______.

Beta Decay:  Atoms that lie above the band of stability will undergo beta decay.  The source of the beta particle is a neutron. Beta decay will increase the number of protons.

 Beta Decay of -14:

Alpha Decay:  Atoms with more than 83 protons will decay automatically. The number of neutrons and protons need to be reduced. An alpha particle is the same as the nucleus of a atom.

 Alpha Decay of -210:

Unit 2 6

Positron Emission:  Isotopes that lie below the band of stability will undergo emission.  The source of a positron is a proton. The number of protons will decrease.

 Positron Emission of Carbon-11:

Electron Capture:  Isotopes that lie below the band of stability can undergo .  A proton incorporates an inner shell electron and forms a neutron. This will decrease the number of protons.

 Electron Capture of Aluminum-26:

Gamma Radiation:  A release of energy, no change in mass occurs.  There is no charge.  Gamma rays are assumed to be released in all forms of decay.

Radiation Change in Change in Particle Mass Charge Type Mass # Atomic # Decrease Decreases Alpha Decay by 4 by 2 No Increases Beta Decay Change by 1 Positron No Decreases

Emission Change by 1 Electron No Decreases

Capture Change by 1 Gamma No N/C Radiation Change

Unit 2 7

Half-life Notes

- Every radioisotope has a characteristic rate of decay - Half-life is the time required for one half of a radioisotope’s nuclei to decay After each half life of a radioisisotope, half of the original radioactive atoms have decayed into atoms of a different isotope (or atom) Formula for calculating half-lives:

mf: mo: t: t1/2: n:

Example 1: -21 has a half-life of 5.0 seconds. If you start with 25 g of fluorine-21, how many grams would remain after 60.0 s?

Unit 2 8

2-A: Atomic Structure Worksheet

Complete the table and then answer the questions below: Element Symbol Protons neutrons electrons Atomic # Mass #

Hydrogen 1 1

H-2

Helium 2 4

Mg-24

Carbon 6 6

H-3

Oxygen 8 8

Cl-36

Neon 10 10 20

Aluminum 13 27

O-18

238 U92

Mg2+ 24

Cl- 35

Zinc 30 30 65

Rb+1 85

P-3 31

1. What is the mass number of carbon?

2. What is the atomic number of oxygen?

3. How many electrons does an atom of aluminum contain?

4. An atom of which element contains two neutrons?

5. Which element has mass number of 16?

Unit 2 9

2-A: Average Atomic Mass Worksheet:

6. There are 2 isotopes of that occur naturally; 63Cu and 65Cu. The63Cu atoms have a mass of 62.929601 amu and the 65Cu atoms have a mass of 64.927794 amu. What is the percent for each isotope?

7. There are 2 isotopes of that occur naturally; 69Ga and 71Ga. The 69Ga atoms have a mass of 68.925581 amu and the 71Ga atoms have a mass of 70.924707 amu. What is the percent natural abundance for each isotope?

8. is composed essentially of two isotopes: 191Ir and 193Ir. The average mass of an iridium atom is 192.217 amu. Determine the natural abundance of each of these isotopes in a naturally occurring sample. (The mass of an 191Ir atom is 190.961 amu, and the mass of an193Ir atom is 192.963 amu.)

Unit 2 10

2-B: Radioactive Decay and Half Life Worksheet Write the reaction that represents the following: 1. Alpha decay of Polonium – 218.

2. Electron capture of – 142.

3. Beta decay of – 43.

4. Alpha decay of – 233

5. Beta decay of – 13.

6. Positron emission of Carbon – 14.

7. Alpha decay of – 196.

8. Electron capture of – 201.

9. Alpha decay of – 226.

10. Beta decay of – 136.

Unit 2 11

2-B: Complete the following half-life problems. Show ALL work. 11. The half-life of – 239 is 24,100 years Of an original mass of 100. g, how much remains after 96,440 years?

12. Exactly 1/16 of a given amount of -234 remains after 26.76 hours. What is the half life of protactinium – 234?

13. How many milligrams remain of a 15.0 mg sample of – 226 after 6396 years? The half-life of radium – 226 is 1599 years.

14. – 99 has been used as a radiographic agent in bone scans. If 99Tc has a half-life of 6.0 hours, what fraction of the administered 100.0 g dose will remain after 2.0 days?

Unit 2 12

Unit 2 Review:

Matching: Match the person in column B to the experiment, discovery or model in column A. Each person can be used more multiple times. Column A Column B 1. ____ Billiard Ball model a. Chadwick 2. ____Cathode Ray tube experiment b. Democritus 3. ____ Atoms are mostly empty space c. Rutherford 4. ____ Began Atomic Theory d. Thomson 5. ____ Atoms are the smallest unit of matter e. Dalton 6. ____ Plum Pudding model 7. ____ Gold Foil Experiment 8. ____ Neutrons make up the rest of the mass of the nucleus. 9. ____ Atoms are divisible into smaller particles. Standard Nuclear Notation: Write the following in standard nuclear notation. 10. An element with 14 electrons and 16 neutrons 12. - 249

11. Potassium with 22 neutrons 13. - 257

Average Atomic Mass: Show ALL work! 14. Nitrogen has two isotopes. Nitrogen- 14 has a mass of 14.003074 amu and a percent abundance of 99.63 %. Nitrogen- 15 has a mass of 15.000108 amu and a percent abundance of 0.37. Calculate the average atomic mass of Nitrogen.

15. Calculate the average atomic mass of the unknown element. Identify this element. Isotope Atomic Mass (amu) Percent Abundance (%) X 23.9850423 78.99 Y 24.9858374 10.00 Z 25.9825937 11.01

Decay: Determine if the following isotopes are stable and explain your answer. 16. Mercury- 200

17. - 124

18. - 106

Unit 2 13

Write the balanced equation for the following nuclear decay. Indicate if the starting isotope was above or below the band of stability for Beta decay, Electron capture and positron emission. 19. Alpha decay of Americum- 241

20. Beta decay of Hydrogen- 3

21. Electron capture of Aluminum- 26

22. Positron emission of Carbon- 11

23. Alpha decay of - 192

Half-life- Show ALL work! 24. After 4 half-lives, what mass of a 64.00 mg sample is remaining?

25. - 72 has a half live of 26.0 hours. What percent of Arsenic- 72 will remain after 78.0 hours?

26. Flourine-18 undergoes positron emission and has a half-life of 1.8 hours. Answer the following questions about this isotope. a. Write the balance equation for the nuclear decay of Fluorine- 18.

b. Determine if the daughter product of Fluorine- 18 is stable.

c. Calculate the mass of Flourine-18 that will remain in a 8.00 g sample after 4 half- lives.

d. Calculate the time that passed in part c.

Unit 2 14

33. If the passing of five half-lives leaves 25.0 mg of a -90 sample, how much was present initially?

34. Compare and contrast the models of the atom proposed by Thompson and Rutherford.

42. Why are electrons in a cathode-ray tube deflected by electric fields?

43. What was Henry Mosley’s contribution to the modern understanding of the atom?

44. What experiment did Rutherford complete and how did it discount the previous model? (Be sure to mention both Rutherford’s model and the previous model)

45. Complete the following table:

Isotope Zn-64

Atomic Number 9 11

Mass Number 32 23

Number of 16 Protons Number of 24 10 Neutrons Number of 20 Electrons

Unit 2 15

46. Calculate the average atomic mass of using the information in the table: Isotope Atomic Mass Fractional (amu) Abundance Ti-46 45.953 8.00 Ti-47 46.952 7.30 Ti-48 47.948 73.800 Ti-49 48.948 5.50 Ti-50 49.945 5.40

47. -230 can be used to provide coloring in glass objects. One method of producing thorium-230 is through the radioactive decay of -230. IS this an example of alpha or beta decay? How do you know?

48. Natural samples of copper contain two isotopes. 63Cu has a mass of 62.930 amu and 65Cu has a mass of 64.928 amu. The average atomic mass of copper is 63.55 amu. Calculate the percent abundance of both isotopes.

Unit 2 16