Download Chapter 4 and 25 Study Guide

Name: ____________________ Period ____
CP Chapter 4 and 25 Study Guide ANSWERS
1.
What were Dalton’s ideas about the atom?
Atoms of the same element are identical
Each element is unique
Atoms combine in fixed ratios to form compounds
2. What are the characteristics of the nucleus of the atom? Small, densely packed, contains protons and
neutrons, contains almost ALL of the mass of the atom
3. What is the mass of a neutron compared to a proton?
About the same
4. What is the nucleus composed of?
Protons and neutrons
5. Why is an atom electrically neutral?
Because the numbers of protons and neutrons are equal
6. How are isotopes of the same element different?
They have a different number of neutrons
7. What are atoms of the same element with different mass numbers called?
Isotopes
8. As the mass number of the isotopes of an element increases, what happens to the number of protons?
Nothing, the number of protons for an element will always stay the same
9. Can atoms of the same element differ in mass number?
Yes, because they can have a different number of neutrons
10. An aluminum isotope consists of 13 protons, 13 electrons and 14 neutrons. What is the mass number?
27 (13 protons + 14 neutrons)
11. Ag-109 has 62 neutrons. How many electrons does it have?
47 (109-62 = 47 protons) protons and electrons are equal in atoms
12. Chlorine has an atomic number 17 and a mass number 36. How many protons, electrons, and neutrons does
it have?
Atomic number = number of protons (17); 17 electrons (neutral atom); 19 neutrons (36-17)
13. Silicon-30 has 14 protons. How many neutrons does it have?
16 neutrons (30-14)
14. Argon (atomic number 18 and mass number 39) has how many protons?
18 (atomic number = number of protons)
15. Which are the heaviest and lightest subatomic particles (neutrons, protons, and electrons)?
Neutrons and protons are heaviest (about the same); electrons are lightest
16. What is the relative mass of protons, neutrons, and electrons?
Protons 1; Neutrons 1; electrons about zero
17. Are atoms positive, negative, or neutral? How does the number of protons relate to the number of
electrons?
Atoms are neutral: number of protons and electrons in atoms are always equal
18. What were Rutherford’s conclusions about the structure of the atom?
Concluded atom is mostly empty space; named nucleus as a small, dense object with a positive charge
19. The atomic number of an element is the total number of which particles IN THE NUCLEUS?
protons
20. In sodium-23, what does the 23 represent?
Mass number
21. Isotopes have a different number of what?
neutrons
Name: ____________________ Period ____
22. How is the number of neutrons in the nucleus of an atom calculated?
Mass number – atomic number =number of neutrons
23. How many neutrons are in 17O? What does the 17 represent?
17 represents mass number; oxygen has atomic number of 8 (17-8 = 9 neutrons)
24. What is mass defect?
The mass lost in a nuclear reaction that is converted to energy
25. What is necessary to calculate the atomic mass of an element?
The weights and percentages of all of the isotopes of that element.
26. What is the correct relationship between mass and energy?
E = mc2
27. What particle is emitted by alpha radiation?
Alpha particle
28. True or false? Between protons in a nucleus, attraction due to nuclear force is greater than repulsion due
to electrostatic force.
True
29. What happens to unstable nuclei?
It undergoes radioactive decay
30. What is a beta particle?
Symbol
; also called an electron
31. What is the change in the atomic number when an atom emits an alpha particle? Beta particle? Gamma
radiation?
Atomic number decreases by 2; increases by 1; stays the same
32. What stops each type of radiation?
Alpha-paper; beta-wood or metal; gamma-lots of lead or concrete
33. What happens in a chain reaction?
the products of the first reaction start the later reactions
218
34. What particle is needed to complete this nuclear reaction 222
86 Rn  84 Po + ___ ?
An alpha particle
35. What is the atomic mass of Boron given: Boron-10 has 19.8% abundance and its mass = 10.013 amu and
Boron-11 has 80.2% abundance and its mass is 11.009 amu.
(0.198)(10.013 amu) + (0.802)(11.009 amu) = 10.8 amu
36. Cobalt-60 has a half-life of 5.272 years. How much of a 100.0 grams sample will be left after five half-lives.
(Hint: There is extra information that you do not need)
Start 100.0 g
1 half life = 50.0 g
2 half lives = 25.0 g
3 half lives = 12.5 g
4 half lives = 6.25 g
5 half lives =3.125 g