Radiochemistry and Radioactivity

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Questions and Answers

What is an isotope with a balanced number of neutrons and protons called?

Ion

Radioisotope

Molecule

Stable isotope (correct)

What happens to the activity of a radioactive source over time?

It increases

It becomes zero immediately

It remains constant

It decreases (correct)

What is a radioisotope?

An inert gas

An isotope that is unstable and emits radiation (correct)

A stable isotope with no radiation

A form of an atom with more electrons

What is the half-life of a radioactive source?

The time taken for the activity to fall to half its original value Signup and view all the answers

What occurs during the decay process of a radioisotope?

The radioisotope becomes less radioactive over time Signup and view all the answers

Which statement best explains why a radioisotope becomes weaker over time?

It becomes stable Signup and view all the answers

What did early investigations by Becquerel, the Curies, Rutherford, and Soddy show?

The activity of a radioactive source reduces over time Signup and view all the answers

How does the activity of a radioactive source fall over time?

At an exponentially decreasing rate Signup and view all the answers

What is the charge of a gamma ray?

0 Signup and view all the answers

Which type of decay involves the emission of a helium nucleus?

Alpha decay Signup and view all the answers

What is the general equation for beta decay?

$ ^{A}{Z}X ightarrow ^{A-1}{Z+1}Y + ^0_-1e $ Signup and view all the answers

What occurs during ionization?

An electron gains enough energy to break away from an atom. Signup and view all the answers

Which particle has a charge of 1+?

Positron Signup and view all the answers

What is the result of the beta decay of carbon-14?

Nitrogen-14 Signup and view all the answers

What type of radiation is emitted when an excited nucleus returns to its ground state?

Gamma ray Signup and view all the answers

Which nuclear reaction correctly represents the alpha decay of radium-226?

$ ^{226}{88}Ra \rightarrow ^{222}{86}Rn + ^4_2\alpha $ Signup and view all the answers

Which of the following types of radiation is known to cause 10 times more biological damage than beta radiation of the same energy?

Alpha radiation Signup and view all the answers

Which process is dominant for high radiation levels?

Direct action Signup and view all the answers

Approximately how much of x-ray damage is due to indirect action?

2/3 Signup and view all the answers

Which of the following is NOT a common method of detecting ionizing radiation?

Thermoluminescent dosimeter Signup and view all the answers

What is the medium used in gas-filled detectors for detecting ionizing radiation?

Gas Signup and view all the answers

What type of radiation do gas-filled detectors primarily measure?

Gamma-rays and beta-particles Signup and view all the answers

Which isotope has a half-life of 8 days?

I-131 Signup and view all the answers

Which isotope is used in the treatment of leukemia?

P-32 Signup and view all the answers

Which isotope has a half-life of 15 hours?

Na-24 Signup and view all the answers

For which type of cancer is Co-60 primarily used?

Different types of cancer Signup and view all the answers

Which isotope has the longest half-life among the ones listed?

Fe-59 Signup and view all the answers

What does the mass number (A) represent in the nuclide $^{127}I_{53}$?

The total number of nucleons Signup and view all the answers

What is the charge of an alpha particle?

+2 Signup and view all the answers

Which type of radiation is a stream of electrons?

Beta radiation Signup and view all the answers

Which type of radiation is a form of high-energy electromagnetic wave?

Gamma radiation Signup and view all the answers

How many protons does the nuclide $^{127}I_{53}$ have?

53 Signup and view all the answers

What kind of radiation causes skin burns?

Beta radiation Signup and view all the answers

What does radioactivity involve?

Spontaneous emission of energetic radiations Signup and view all the answers

Which of the following isotopes is naturally present in our bodies?

Potassium-40 Signup and view all the answers

What are the protons and neutrons in the nucleus collectively called?

Nucleons Signup and view all the answers

What is the SI unit for measuring radioactivity?

Becquerel Signup and view all the answers

How many disintegrations per second are equivalent to one curie?

3.7 x 10^10 Signup and view all the answers

What is the atomic number of an atom symbolized by?

Z Signup and view all the answers

What is the charge of a neutron?

0 unit Signup and view all the answers

Which isotope of hydrogen contains two neutrons?

Tritium Signup and view all the answers

Which uranium isotope has 92 protons and 146 neutrons?

Uranium-238 Signup and view all the answers

What is the overall charge on an atom in its normal state?

Zero Signup and view all the answers

Which of the following isotopes is specifically produced for medical use?

Iodine-131 Signup and view all the answers

Approximately how much heavier is a nucleon compared to an electron?

What holds the electrons in orbit around the nucleus?

Electrostatic attraction Signup and view all the answers

What distinguishes isotopes of the same element from each other?

Number of neutrons Signup and view all the answers

How is the mass number, A, of an atom calculated?

A = Z + N Signup and view all the answers

What term describes a particular nuclear species with a given combination of A and Z?

Nuclide Signup and view all the answers

What type of energy does ionizing radiation possess compared to non-ionizing radiation?

More energy Signup and view all the answers

Which type of radiation is at the upper end of the electromagnetic spectrum?

X-ray and gamma ray radiation Signup and view all the answers

What happens to an atom when exposed to very high-energy ionizing radiation?

The atom loses electrons or the nucleus breaks up Signup and view all the answers

Which tissue type is particularly sensitive to radiation damage?

Bone marrow Signup and view all the answers

Which particles are around twenty times as effective at killing cells compared to beta particles, gamma rays or X-rays?

Alpha particles Signup and view all the answers

What is the unit for absorbed dose of radiation?

RAD Signup and view all the answers

What does REM stand for in the context of radiation dose measurements?

Relative Biological Equivalence Signup and view all the answers

How much energy is equal to one rad?

$2.4 \times 10^{-3}$ cal Signup and view all the answers

Study Notes

Radiochemistry

Radioactivity is a natural phenomenon that occurs in certain substances, where atoms emit invisible and energetic radiations that can penetrate materials opaque to visible light.
These radiations can be harmful to live cells, but they have beneficial applications in medicine when used correctly.

Units of Radioactivity

The amount of radioactivity is measured by the rate of radioactive disintegration per second.
The Curie (Ci) is a unit of radioactivity, equivalent to 3.7 x 10^10 disintegrations per second.
1 Curie is equal to 3.7 x 10^10 Becquerel.

Isotopes

An isotope is a variant of a chemical element, with the same number of protons (atomic number) but a different number of neutrons.
Isotopes can be stable or radioactive, and radioisotopes undergo spontaneous decay and emit radiation.
The stability of an isotope depends on the balance of neutrons and protons.

Radioisotopes

Radioisotopes are isotopes that undergo spontaneous decay and emit radiation.
They become less radioactive over time, eventually becoming stable.
The half-life of a radioisotope is the time it takes for the activity to fall to half of its original value.

Half-Life

The half-life of a radioactive source is the time it takes for the activity to fall to half of its original value.
The activity of a radioisotope decreases exponentially with time, halving every half-life.
The half-life of a radioisotope is different for each substance.

The Atom

An atom is the smallest unit of matter, consisting of a nucleus and orbiting electrons.
The nucleus is composed of protons and neutrons, and the number of protons determines the atomic number (Z).
The atomic number and mass number (A) determine the identity of an element.

Structure of the Atom

The nucleus is composed of protons and neutrons.
The atomic number (Z) is the number of protons in the nucleus.
The mass number (A) is the sum of protons and neutrons in the nucleus.

Types of Radiation

Alpha radiation is a stream of particles with two protons and two neutrons, having a charge of +2.
Beta radiation is a stream of electrons, resulting from the transformation of a neutron into a proton and electron.
Gamma radiation is a form of energy, similar to light waves or X-rays, with high energy and penetration.
Electron Capture or Ionization radiation is a process where an electron is given enough energy to break away from an atom.

Nuclear Reaction

Nuclear reactions involve the collision of atomic nuclei or a nucleus and a subatomic particle.
The resulting nuclides are different from the parent nuclei.

Forms and Properties of Nuclear Radiation

Alpha radiation has a charge of +2 and a symbol of α or 4He.
Beta radiation has a charge of -1 and a symbol of β or -10e.
Gamma radiation has a charge of 0 and a symbol of γ.
Positron radiation has a charge of +1 and a symbol of +10e.
Neutron radiation has a charge of 0 and a symbol of n.

Ionization Radiation

Ionization radiation is the process where an electron is given enough energy to break away from an atom.
This results in the formation of two charged particles or ions: a positively charged molecule and a negatively charged electron.

Alpha Decay

Alpha decay occurs when a nucleus with a mass number greater than 200 liberates a helium nucleus (alpha particle).
The general equation for alpha decay is: A-ZX → A-4Z-2X + α.

Beta Decay

Beta decay occurs when a neutron is converted into a proton, accompanied by the emission of a beta particle (high-energy electron).
The equation for beta decay is: A-ZX → A-Z+1X + -10e.

Gamma Emission

Gamma emission occurs when an excited nucleus returns to its ground state, accompanied by the emission of a high-energy photon.
The equation for gamma emission is: A-ZX → A-ZX + γ.

Ionizing Radiation

Ionizing radiation is energy produced from natural or artificial sources, with enough energy to cause chemical changes in living tissue.
X-ray and gamma ray radiation are at the upper end of the electromagnetic spectrum, with high frequencies and short wavelengths.
Ionizing radiation deposits a large amount of energy into a small area, disrupting chemical bonds and causing damage.

Radiation Dose

Radiation dose measures the energy deposited by ionizing radiation in a material.
The concept of absorbed dose applies to all types of material, but when assessing biological effects, the equivalent dose is used, which takes into account the radiation weighting factor.
The equivalent dose is measured in units of Rem, which is 1 rad multiplied by the relative biological equivalence (RBE).

Units of Radiation Dose

Rad is a unit of radiation dose, equivalent to 2.4 x 10^-3 cal of energy absorbed by 1 kg of tissue.
Rem is a unit of radiation dose, equivalent to 1 rad multiplied by the RBE.

Direct and Indirect Action

Direct action occurs when the atoms of the target are ionized by the radiation.
Indirect action occurs when the radiation interacts with other cellular molecules, producing free radicals that damage the target.

Radiation Detectors

The three methods of detecting ionizing radiation are the photographic method, scintillation counter, and Geiger counter.
Geiger counters are gas-filled detectors that use an electric potential to collect electrons released by ionizing radiation.

Medical Applications of Isotopes

The half-life of an isotope must be long enough for it to do its job and short enough to eliminate it from the body.
In medical applications, no alpha radiation is used due to its damaging effects on tissues.
The main mechanism for isotopes application is either externally (such as Co-60) or internally (such as I-131).
The table below shows the main isotopes used in medical applications:

Isotopes	Half-life	Application
I-131	8 days	Thyroid cancer
Co-60	5.3 years	Different types of cancer
P-32	143 days	Leukemia
Na-24	15 hrs	Circulation system
Fe-59	456 days	Red blood cells

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Description

Learn about the natural phenomenon of radioactivity, its effects on living cells, and its beneficial applications in medicine.