Chapter 21: Radioactivity and Nuclear Chemistry Flashcards Preview

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Flashcards in Chapter 21: Radioactivity and Nuclear Chemistry Deck (36)
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1

Radioactivity

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

2

Phosphorescence

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

3

Natural radioactivity

- 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

4

A X
Z

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

5

Nuclide

Particular isotope (or species) of an element

6

- Proton Symbol
- Neutron Symbol
- Electron Symbol

1
1 p

1
0 n

0
-1 e

7

Alpha decay

- 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

8

Ionizing power

- Ability of radiation to ionize other molecules and atoms

9

Penetrating power

- Ability to penetrate molecules

10

Beta decay

- Occurs when an unstable nuclide emits an electron
- Lower ionizing power; higher penetrating power

11

Gamma ray emission

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

12

Positron

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

13

Electron capture

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

14

Nucleons

- Collection of protons and neutrons in nucleus

15

N/Z Ratio

- 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

16

Magic numbers

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

17

Film-badge dosimeters

Photographic held in small case pinned to clothing; monitors exposure

18

Geiger-Muller counter

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

19

Scintillation counter

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

20

Rate of decay in proportion to nuclei (equation)

Rate = kN
- k: rate constant
- N: number of radioactive nuclei

21

Half-life and equation

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

22

Integrated rate law

Concentration of reactant as function of time

23

Radiometric dating

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

24

Radiocarbon dating

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

25

Nuclear fission

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

26

Critical mass

Enough of substance to create self-sustaining reaction

27

Matter lost and Matter formed

E = mc^2

28

Mass defect

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

29

Nuclear binding energy

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

30

Nuclear fusion

- Combination of two light nuclei to form heavier one

31

Transmutation

Nuclear reaction that results in transformation of one element into another

32

Radiation effects on life

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

33

Radiotracer

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

34

Positron emission topography (PET)

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

35

Radiotherapy

Used as means to treat cancer

36

Calculating mass defect

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