CHAPTER NINE: NUCLEAR RADIATION Flashcards
Most naturally occurring isotopes of elements up to atomic number ____ have stable nuclei, which means that __________.
19; the forces of attraction and repulsion between the protons and neutrons are balanced.
Elements with atomic numbers ____ and higher usually have one or more isotopes that have unstable nuclei, which means that ____________.
20; too many or too few protons compared to the number of newborns, which means the forces between protons and neutrons are unbalanced.
What is RADIATION?
An unstable nucleus is RADIOACTIVE, which means that it spontaneously emits small particles of energy called RADIATION, to become more stable.
Radiation may take the form of particles such as alpha and beta particles, or pure energy such as gamma rays.
What is a RADIOISOTOPE?
An isotope that emits radiation.
For most types of radiation, there is a change in the number of ________ in the nucleus, which means that an atom is __________.
protons
converted into an atom of a different element.
Elements with atomic numbers of ____ or higher are produced artificially in the nuclear laboratories and consist only of ________ __________.
93
radioactive isotopes
Remember that the MASS number is equal to the number of __________ and _________ in the nucleus, and the ATOMIC number is equal to the number of ________.
Radioactive isotopes are identified by writing the ________ number after the element’s name or symbol.
protons and neutrons
protons
mass number
Example: iodine-131 OR I-131
TYPES OF RADIATION:
What is an ALPHA PARTICLE? It has a mass number of _____, an atomic number of ___, and a charge of _____.
What is the SYMBOL for an alpha particle?
An ALPHA PARTICLE is identical to a helium (He) nucleus, which has 2 protons and 2 neutrons.
It has a mass number of 4, an atomic number of 2, and a charge of 2+.
The symbol for an alpha particle is the Greek letter alpha OR the symbol of a helium nucleus except that the 2+ charge is omitted.
TYPES OF RADIATION:
What is a BETA PARTICLE?
What is its MASS number?
What is the symbol for a beta particle?
How is a beta particle formed?
Another type of radiation occurs when a radioisotope emits a BETA PARTICLE.
A beta particle is a high-energy electron, with a charge of 1- and, because its mass is so much less than the mass of a proton, it has a mass number of 0.
It is represented by the Greek letter beta OR by the symbol for the electron (e) including the mass number and the charge.
A beta particle forms when a neutron in an unstable nucleus changes to a proton and an electron.
TYPES OF RADIATION:
What is a POSITRON?
What is the symbol for a positron?
How is a positron produced?
A POSITRON has a positive (1+) charge with a mass number of 0, which makes it similar to a beta particle.
A positron is represented by the Greek symbol beta and a +. See page 321 for how the symbols for a beta particle and a positron are written.
A positron is produced by an unstable nucleus when a proton is transformed into a neutron and a positron.
What is ANTIMATTER?
A positron is an example of ANTIMATTER, a term physicists use to describe a particle that is the exact opposite of another particle, in this case, an electron.
What are GAMMA RAYS?
What is the symbol for a gamma ray?
When an electron and a positron collide, their minute masses are completely converted to energy in the form of GAMMA RAYS.
Gamma rays are high-energy radiation, released when an unstable nucleus undergoes a rearrangement of its particles to give a more stable, lower energy nucleus.
Gamma rays are often emitted along with other types of radiation.
A gamma ray is written as the Greek letter gamma (y). They are energy only, so zeros are used to show that a gamma ray has no mass or charge. See page 322
Types of radiation- see Table 9.2
page 322
When working with radioactive isotopes, we must use proper radiation protection, or ________, to prevent exposure.
Shielding
What are the dangers of being exposed to ALPHA PARTICLES and how can you protect yourself?
Alpha particles, which have the greatest mass and highest charge of the radiation particles, travel only a few centimeters in the air before they collide with air molecules, acquire electrons, and become helium atoms.
External sources of protection are provided by a piece of paper, lab coats and the skin.
If ingested or inhaled, alpha particles can cause serious internal damage because of the large mass and high charge.
What are the dangers of being exposed to BETA PARTICLES and how can you protect yourself?
Beta particles have a very small mass and move much faster and farther than alpha particles, traveling as much as several meters through the air. They can pass through paper and penetrate a far as 4-5 mm into body tissue.
External exposure to beta particles can burn the surface of the skin, but the are stopped before they reach the internal organs.
Heavy clothing such a lab coats and gloves are needed to protect the skin from beta particles.
What are the dangers of being exposed to GAMMA RAYS and how can you protect yourself?
Gamma rays travel great distances through the air and pass through many materials, including body tissues. Because gamma rays can penetrate so deeply, exposure to these rays is extremely hazardous. Only very dense shielding, such as lead or concrete, will stop them.
When working with radioactive materials, wear protective clothing and gloves and stand behind a shield. Long tongs may be used to pick up vials of radioactive material, keeping them away from the hands and body. See page 323, Table 9.3 for a summary of properties of ionizing radiation and shielding required.
The greater the distance from the radioactive source, the _______ the intensity of radiation you receive.
By doubling your distance from the radiation source, the intensity of radiation ____ to ________.
lower
drops to 1/4 of its previous value
What is RADIOACTIVE DECAY?
How is this process written?
An arrow between the atomic symbols indicates that this is a ________ equation.
A nucleus spontaneously breaks down by emitting radiation.
This process can be written using the atomic symbols of the original radioactive nucleus, the new nucleus and the radiation emitted.
nuclear equation. See page 324 for the equation.
In a nuclear equation, the mass numbers and the atomic numbers must _________ so the number of protons and neutrons are _______________.
However, in a nuclear equation, there is often a change in the number of _______, which gives a different _______.
balance; equal on both sides
protons, element
What is ALPHA DECAY?
An unstable nucleus undergoes alpha decay by emitting an alpha particle.
Because an alpha particle consists of 2 protons and 2 neutrons, the mass number decreases by 4 and the atomic number decreases by 2.
What is BETA DECAY?
The formation of a beta particle is the result of the breakdown of a neutron into a proton and an electron (beta particle). Because the proton remains in the nucleus, the number of protons increases by one, while the number of neutrons decreases by one.
In a nuclear equation for beta decay, the mass number of the radioactive nucleus and the mass number of the ne nucleus are the same.
However, the atomic number of the new nucleus increases by one, indicating a change of one element into another.
What is a POSITRON EMISSION?
In a positron emission, a proton in an unstable nucleus is converted to a neutron and a positron. The neutron remains in the nucleus, but the positron is emitted from the nucleus.
In a nuclear equation for positron emission, the mass number of the radioactive nucleus and the mass number of the new nucleus are the same.
However, the atomic number of the new nucleus decreases by one, indicating a change of one element into another.
What is GAMMA EMISSION?
In radiology, one of the most commonly used gamma emitters is _______.
By emitting energy in the form of gamma rays, the unstable nucleus becomes ___ ____.
Pure gamma emitters are rare, although some gamma radiation accompanies most alpha and beta radiation.
technetium (Tc)- the unstable isotope decays quickly and it is written as the metastable (m) isotope: technetium-99m
more stable
