Chapter 21: Radioactivity and Nuclear Chemistry

Question 1

Radioactivity

Answer 1

• Emission of subatomic particles or high-energy electromagnetic radiation by nuclei of certain atoms

Question 2

Phosphorescence

Answer 2

• Long-lived emission of light following absorption of light by certain atoms and molecules

Question 3

Natural radioactivity

Answer 3

• Emission produced by nuclei of radioactive atoms; unstable and spontaneously decompose (emit small pieces)
• Include alpha decay, beta decay, gamma ray emission, and positron emission

Question 4

A X

Z

Answer 4

A = Mass number; sum of protons and neutrons in nucleus
Z =  Atomic number; Number of protons in nucleus
X = Chemical symbol

Question 5

Nuclide

Answer 5

Particular isotope (or species) of an element

Question 6

• Proton Symbol
• Neutron Symbol
• Electron Symbol

Answer 6

1
1 p

1
0 n

0
-1 e

Question 7

Alpha decay

Answer 7

• Occurs when an unstable nucleus emits a particle composed of two protons and two neutrons
• Particle: 4/2 He (written as chemical, not a fraction)
• When emitting a particle, number of protons change
• Highest ionizing power
• Lowest penetrating power

Question 8

Ionizing power

Answer 8

• Ability of radiation to ionize other molecules and atoms

Question 9

Penetrating power

Answer 9

• Ability to penetrate molecules

Question 10

Beta decay

Answer 10

• Occurs when an unstable nuclide emits an electron

- Lower ionizing power; higher penetrating power

Question 11

Gamma ray emission

Answer 11

• Form of electromagnetic radiation; high energy photons
• No charge and no mass
• Highest penetrating power and lowest ionizing power

Question 12

Positron

Answer 12

• Occurs when an unstable nucleus emits a positron (antiparticle of the electron– 0/+1 e)

Question 13

Electron capture

Answer 13

Nucleus assimilates an electron from the inner orbital or its electron cloud

Question 14

Nucleons

Answer 14

• Collection of protons and neutrons in nucleus

Question 15

N/Z Ratio

Answer 15

• Helps determine nuclear stability
• too high: tends to convert neutrons to protons through beta decay
• Too low: Too many protons; tends to convert protons to neutrons via positron emission or electron capture

Question 16

Magic numbers

Answer 16

Nuclide with a certain number of nucleons that are uniquely stable; these numbers are even

Question 17

Film-badge dosimeters

Answer 17

Photographic held in small case pinned to clothing; monitors exposure

Question 18

Geiger-Muller counter

Answer 18

Particles emitted pass through Ar filled chamber; create radioactive argon; make clicks

Question 19

Scintillation counter

Answer 19

• Radioactive emissions pass through material that emits UV; excites to higher energy state and emits light

Question 20

Rate of decay in proportion to nuclei (equation)

Answer 20

Rate = kN

• k: rate constant
• N: number of radioactive nuclei

Question 21

Half-life and equation

Answer 21

• Time it takes for 1/2 the parent nuclides in radioactive sample to decay to daughter nuclides
• t 1/2 = 0.693/k

Question 22

Integrated rate law

Answer 22

Concentration of reactant as function of time

Question 23

Radiometric dating

Answer 23

Radiometric isotopes and predictable decay are used to estimate age of rocks and artifacts containing those isotope

Question 24

Radiocarbon dating

Answer 24

Used to estimate age of artifacts and fossil (C-14 : C-12 ratio)

Question 25

Nuclear fission

Answer 25

- Splitting of the uranium atom (usually from bombardment of uranium)

Question 26

Critical mass

Answer 26

Enough of substance to create self-sustaining reaction

Question 27

Matter lost and Matter formed

Answer 27

E = mc^2

Question 28

Mass defect

Answer 28

Difference in mass between sum of masses of separate components and actual mass

Question 29

Nuclear binding energy

Answer 29

Amount of energy required to break apart the nucleus into its separate component nucleons

Question 30

Nuclear fusion

Answer 30

- Combination of two light nuclei to form heavier one

Question 31

Transmutation

Answer 31

Nuclear reaction that results in transformation of one element into another

Question 32

Radiation effects on life

Answer 32

- Acute radiation damage - Increased cancer risk - Genetic defects - Measure radiation exposure in terms of decay events exposed to or Energy absorbed per body tissue

Question 33

Radiotracer

Answer 33

Radioactive nuclide attached to a compound and introduce to a mixture to track movement in the body

Question 34

Positron emission topography (PET)

Answer 34

Employs positron emitting nuclides; attached to glucose and administered to patient to use gamma rays to map metabolism and structural features of the imaged organ

Question 35

Radiotherapy

Answer 35

Used as means to treat cancer

Question 36

Calculating mass defect

Answer 36

Z(p+ mass) + (A-Z)(n mass) - mass isotope