Chapter 21 Flashcards
What is radioactivity?
It is the emission of subatomic particles or high-energy electromagnetic radiation by the nuclei of certain atoms. Atoms that emit radiation are said to be radioactive
What is phosphorenscence?
It is the long-lived emission of light by atoms or molecules that sometimes occurs after they absorb light
How are X-rays detected?
By their ability to penetrate matter and expose a photographic plate
Every atom of an element has the same number of _______, which is represented by the atomic number (Z)
Protons
Atoms of the same elements can have different numbers of _______, and are called isotopes
neutrons
How are isotopes identified?
By their mass number
How do we find the number of neutrons?
We subtract the atomic number from the mass number
How many protons and neutrons are there in the isotope 2713Al?
14 neutrons and 13 protons
What are the three types of radioactive rays discovered by Rutherford?
Alpha, beta, and gama
What are positrons and electron capture?
Positrons are similar to a positively charged electron emitted by unstable nuclei
Electron capture happens when a low energy electron is pulled into the nucleus
Gamma rays
Possess neither mass or change, it has the strongest penetrating power
Beta rays
It is symbolized as 0-1ß, it is a high speed electron
Alpha rays
It has the weakest penetrating power, it is the largest of all the components, it is symbolized as 42He
What is alpha decay?
- Occurs when an unstable nucleus emits a particle composed of two protons and two neutrons
- Most ionizing but least penetrating of the types of radioactivity
- Loss of an alpha particle means
–the atomic number decreases by 2, and
–the mass number decreases by 4.
What is the ionizing power?
The ability of radiation to ionize other molecules and atoms
Of all types of radioactivity, alpha radiation has the highest ionizing power.
What is the penetrating power?
The ability to penetrate through matter
Alpha radiation does not easily penetrate into cells because it can be stopped by a sheet of paper, by clothing, or even by air.
What is beta decay?
- Occurs when an unstable nucleus emits an electron
- About 10 times more penetrating than α but only about half the ionizing ability
- When an atom loses a β particle its
–atomic number increases by 1, and
–the mass number remains the same.
What is the gamma emission
- Gamma (γ) rays are high-energy photons of light.
- No loss of particles from the nucleus
- No change in the composition of the nucleus
–Same atomic number and mass number
- Least ionizing but most penetrating
- Generally occurs after the nucleus undergoes some other type of decay and the remaining particles rearrange
If the room next door contains an alpha emitter, a beta emitter, and a gamma emitter, all with similar activities, which particles are you most likely to detect in the room you are in?
Gamma rays
What is the positron emission?
•Positron has a charge of +1 and a negligible mass.
–Antiparticle of electron
- Similar to beta particles in their ionizing and penetrating ability
- When an atom loses a positron from the nucleus, its
–mass number remains the same, and
–its atomic number decreases by 1.
•Positrons result from a proton changing into a neutron.
It is similar to the beta particles but as the opposite
What happens during an electron capture?
- Occurs when an inner orbital electron is pulled into the nucleus
- No particle emission, but atom changes
–Same result as positron emission
Only situation where the parent nuclide is affected and not the daughter nuclide
What is the importance of the N/Z ratio?
•The ratio of neutrons: protons; is an important measure of the stability of the nucleus.
- If the N/Z ratio is too high, neutrons are converted to protons via β decay.
- If the N/Z ratio is too low, protons are converted to neutrons via positron emission or electron capture.
–Or via α decay, though not as efficiently
What is the decay series?
Wehn all of the radioactive nuclides are produced one after the other until a stable nuclide is reached
A Geiger-Muller counter and, a scintillation counter and a thermoluminiscent dosimeter are istruments important for what?
Detecting radioacitivity
As most chemical reactions, the rate of radioactive change is affected by temperature.
False, it is not affected by temperature
•The _______ the half-life, the more nuclei decay every second; therefore, we say the sample is ______”
Shorter; hotter
Consider this graph representing the decay of a radioactive nuclide. What is the half-life of the nuclide?
a. 625 years
b. 1250 years
c. 2500 years
d. 3125 years
1250 years
Which elements are used in radiometric dating?
potassium-40 to argon-40
The radioactive decay of ________ is the single greatest source of human exposure to radiation
Radon
The combination of two light nuclei to form a heavier nuclei is called
Nuclear fusion
Identify the nuclide used to study bones.
technetium-99m
Identify the radiotracer used to study the thyroid.
iodine-131
A major medical use of fluorine-18 is _____.
in positron emission tomography (PET) to image the brain and heart
What is nuclear fission?
when a large nucleus splits into two
smaller nuclei via reaction with
neutron
What is nuclear fusion?
When small nuclei can be accelerated to
smash together to make a larger
nucleus.
Who releases more energy, fusion or fission?
Fusion
What is a chain reaction?
Occurs when a reactant in the process is also a product of the process. It is a self amplifying reaction.
What is the critical mass?
The minimum amount of fissionable isotope needed to
sustain the chain reaction
What are the three types of radiation effects?
acute radiation damage,
increased cancer risk, and genetic effects
What is exposure?
the number of decay events to which a person is
exposed
Dose
the amount of energy actually absorbed by body tissue
What is s nuclide?
a particular isotope of an element
Describe what changes occur during gamma ray emission.
The mass number and atomic number do not change.
Which type of radioactivity changes the mass of the isotope the most?
alpha particle
