Chapter 21: Radioactivity and Nuclear Chemistry Flashcards
Radioactivity
- Emission of subatomic particles or high-energy electromagnetic radiation by nuclei of certain atoms
Phosphorescence
- Long-lived emission of light following absorption of light by certain atoms and molecules
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
A X
Z
A = Mass number; sum of protons and neutrons in nucleus Z = Atomic number; Number of protons in nucleus X = Chemical symbol
Nuclide
Particular isotope (or species) of an element
- Proton Symbol
- Neutron Symbol
- Electron Symbol
1
1 p
1
0 n
0
-1 e
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
Ionizing power
- Ability of radiation to ionize other molecules and atoms
Penetrating power
- Ability to penetrate molecules
Beta decay
- Occurs when an unstable nuclide emits an electron
- Lower ionizing power; higher penetrating power
Gamma ray emission
- Form of electromagnetic radiation; high energy photons
- No charge and no mass
- Highest penetrating power and lowest ionizing power
Positron
- Occurs when an unstable nucleus emits a positron (antiparticle of the electron– 0/+1 e)
Electron capture
Nucleus assimilates an electron from the inner orbital or its electron cloud
Nucleons
- Collection of protons and neutrons in nucleus
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
Magic numbers
Nuclide with a certain number of nucleons that are uniquely stable; these numbers are even
Film-badge dosimeters
Photographic held in small case pinned to clothing; monitors exposure
Geiger-Muller counter
Particles emitted pass through Ar filled chamber; create radioactive argon; make clicks
Scintillation counter
- Radioactive emissions pass through material that emits UV; excites to higher energy state and emits light
Rate of decay in proportion to nuclei (equation)
Rate = kN
- k: rate constant
- N: number of radioactive nuclei
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
Integrated rate law
Concentration of reactant as function of time
Radiometric dating
Radiometric isotopes and predictable decay are used to estimate age of rocks and artifacts containing those isotope
Radiocarbon dating
Used to estimate age of artifacts and fossil (C-14 : C-12 ratio)
Nuclear fission
- Splitting of the uranium atom (usually from bombardment of uranium)
Critical mass
Enough of substance to create self-sustaining reaction
Matter lost and Matter formed
E = mc^2
Mass defect
Difference in mass between sum of masses of separate components and actual mass
Nuclear binding energy
Amount of energy required to break apart the nucleus into its separate component nucleons
Nuclear fusion
- Combination of two light nuclei to form heavier one
Transmutation
Nuclear reaction that results in transformation of one element into another
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
Radiotracer
Radioactive nuclide attached to a compound and introduce to a mixture to track movement in the body
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
Radiotherapy
Used as means to treat cancer
Calculating mass defect
Z(p+ mass) + (A-Z)(n mass) - mass isotope
