Module 13 (Use the Periodic Chart to answer these questions. You will be able to use it on the test.)

Question 1

1a. define: model

Answer 1

a schematic description of a system that accounts for its known properties

Question 2

1b. define: nucleus

Answer 2

the center of an atom, containing the protons and neutrons

Question 3

1c. define: atomic number

Answer 3

the number of protons in an atom

Question 4

1d. define: mass number

Answer 4

the sum of the number os neutons and protons in the nucleus of an atom

Question 5

1e. define: isotopes

Answer 5

atoms with the same number of protons but different numbers of neutrons

Question 6

1f. define: element

Answer 6

a collection of atoms that all have the same number of protons

Question 7

1g. define: radioactive isotope

Answer 7

an atom with a neucleus that is not stable

Question 8

1h. define: half-life

Answer 8

the time it takes for half of the original sample of a radioactive isotope to decay

Question 9

2. Order the three constituent parts of the atom in terms of their mass, from least massive to most massive.

Answer 9

electron, proton, neutron

Question 10

3. What force keeps the protons and neutrons in the nucleus? What causes this force?

Answer 10

the nuclear force; this force is caused by the exchange of pions between protons and/or neutrons

Question 11

4. What force keeps the electrons orbiting around the nucleus?

Answer 11

electromagnetic force

Question 12

5. What is an atom mostly made of?

Answer 12

mostly empty space

Question 13

6. An atom has an atomic number of 34. How many protons and electrons does it have? What is its symbol?

Answer 13

34 electrons and 34 protons; Se

Question 14

7. List the number of protons, electrons and neutrons for each of the following atoms:

a. Neon- 20 (neon’s chemical symbol is “Ne”)
b. 56Fe
c. 139La
d. 24Mg

Answer 14

a. 10 protons, 10 electrons, 10 neutrons
b. 26 protons, 26 electrons, 30 neutrons
c. 57 protons, 57 electrons, 82 neutrons
d. 12 protons, 12 electrons, 12 neutrons

Question 15

8. Two atoms are isotopes. The first has 18 protons and 20 neutrons. The second has 22 neutrons. How many protons does the second atom have?

Answer 15

the second atom also has 18 protons

Question 16

9. Which of the following atoms are isotopes?

112Cd, 112Sn, 120Xe, 124Sn, 40Ar, 120Sn

Answer 16

112Sn, 124Sn, 120Sn

Question 17

10. Draw what the Bohr model says and 16O atom would look like

Answer 17

look in answer key on page 32 #10

Question 18

11. Draw what the Bohr model says a 25Mg atom would look like.

Answer 18

look in answer key on page 32 #11

Question 19

12. What is the largest Bohr orbit in a uranium atom (the symbol for uranium is “U”), and how many electrons are in it?

Answer 19

the largest Bohr orbit is the fifth one, and there are 32 electrons in it

Question 20

13. Why is the strong nuclear force such a short-range force?

Answer 20

Since pions have a very short lifetime, the strong nuclear force can only act over very tiny distances.

Question 21

14. Determine the daughter products produced in the beta decay of the two radioactive isotopes shown below:
    a. 98Tc b. 125I

Answer 21

a- 98Ru

b- 125Xe

Question 22

15. Determine the daughter products produced in the alpha decay of the two radioactive isotopes shown below:
    a. 212Bi b. 224Ra

Answer 22

a- 208Tl

b- 220Rn

Question 23

16. A radioactive isotope goes through radioactive decay, but the isotope’s number of protons and neutrons does not change. What kind of radioactive decay occurred?

Answer 23

gamma decay

Question 24

17. The half-life of the radioactive decay of 226Ra is 1,600 years. If a sample of 226Ra originally had a mass of 10 grams, how many grams of 226Ra would be left after 3200 years?

Answer 24

2.5 grams

Question 25

18. The half-life of the man-made isotope 11C is 20 min. If a scientist makes 1 gram of 11C, how much will be left in one hour?

Answer 25

0.125 grams

Question 26

19. Why is radioactive dating unreliable in most situations?

Answer 26

Radioactive dating is usually unreliable because assumptions must be make as tok the original condition of the object. These assumptions are usually erroneous

Question 27

20. List the three types of radioactive particles discussed in this module in the order of their ability to travel through matter. Start with the particle that cannot pass through much matter before stopping, and end with the one that can pass through most matter before stopping.

Answer 27

Alpha particles pass through the least amount of matter before stopping, beta particles are next, and gamma rays pass through the most matter before stopping.