Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
What is the same for all isotopes of an element?
The number of protons and the number of electrons.
What is different for isotopes of an element?
The number of neutrons and nucleon number.
What is the term for the total number of protons and neutrons in an atom’s nucleus?
Nucleon number.
Do isotopes of the same element have the same chemical properties?
Yes, because they have the same number of electrons.
Do isotopes of the same element have the same physical properties?
No, they have different physical properties like density, melting point, and boiling point.
How is the standard notation for isotopes written?
A X, where A is the nucleon number and X is the element symbol.
What is relative atomic mass?
The weighted average mass of all isotopes of an element, considering their natural abundance.
What is the formula for calculating relative atomic mass?
Relative atomic mass = (∑ (% isotope × mass of isotope))/100.
What are the two main types of isotopes?
Radioactive isotopes (radioisotopes) and non-radioactive isotopes.
What is the key characteristic of radioisotopes?
They are unstable and emit radiation.
Give one medical use of iodine-131.
To detect thyroid problems and treat thyroid cancer.
What is a medical use of Cobalt-60?
To treat cancer with radiotherapy by emitting gamma rays.
What is the use of plutonium-238?
As an energy source for pacemakers.
What is carbon-14 used for in archaeology?
To determine the age of ancient organic materials by radiocarbon dating.
What is phosphorus-32 used for in agriculture?
To study the uptake and metabolism of phosphorus by plants.
What is sodium-24 used for in industry?
To detect leaks in gas or oil pipelines and ventilation systems.
Give one example of an isotope used as a power source.
Uranium-235 is used as fuel in nuclear power stations.
How is gamma radiation from cobalt-60 used in the food industry?
To destroy bacteria that cause food spoilage.
What is a use of Krypton-85 in industry?
To control the thickness of plastic sheets.
Explanation Questions
Explain why isotopes of an element have the same chemical properties but different physical properties.
Isotopes have the same chemical properties because they have the same number of protons and electrons, and thus the same electron configuration and number of valence electrons, which determine chemical reactivity. However, they differ in physical properties (like density, melting, and boiling points) due to the differing number of neutrons, which affects their mass.
Explain the concept of relative atomic mass and why it is calculated using the weighted average of isotopes.
Relative atomic mass is the average mass of all the isotopes of an element, weighted by their natural abundance. It is calculated this way because isotopes occur in different proportions in nature, and a simple average would not accurately reflect the average mass of the atoms in a sample of that element. The weighted average takes into account both the mass of each isotope and how much of it exists in nature.
Describe the steps involved in calculating the relative atomic mass of an element given the mass and abundance of its isotopes.
First, identify all existing isotopes of the element and their individual masses. Second, determine the percentage abundance of each isotope in a naturally occurring sample of the element. Third, multiply the percentage abundance by the mass of each isotope. Fourth, sum the products from the previous step for each isotope and divide by 100 to get the weighted average, which is the relative atomic mass.
Explain the difference between radioactive and non-radioactive isotopes and why the distinction is important for their applications.
Radioactive isotopes (radioisotopes) are unstable and emit radiation as they decay, whereas non-radioactive isotopes are stable. This difference is vital because radioisotopes are useful in applications like medicine, archaeology, and industry due to their ability to emit detectable radiation, and they need to be handled safely. Non-radioactive isotopes do not emit radiation and are therefore used in situations where stability and the absence of radiation are required.
Describe how iodine-131 is used in medicine for both diagnosis and treatment.
Iodine-131 is used in medicine to detect and treat thyroid problems. It can be used to diagnose thyroid disorders by imaging the thyroid gland, as it is readily taken up by the gland. Additionally, the radiation it emits can destroy cancerous thyroid tissue as a form of treatment.
Explain how carbon-14 is used in radiocarbon dating and what information it provides about ancient materials.
Carbon-14 is a radioactive isotope of carbon that is produced in the atmosphere and is incorporated into living organisms. When an organism dies, it no longer takes in carbon-14, and the amount of carbon-14 in the remains decays over time. By measuring the amount of carbon-14 left in ancient organic materials, scientists can estimate how long ago the organism died. This helps in determining the age of fossils, artifacts, and other historical items.
Explain how sodium-24 is used in industry to detect leaks in pipes.
Sodium-24 is a radioactive isotope used as a tracer in pipelines. When a solution containing sodium-24 is injected into a pipeline, radiation detectors placed along the pipe can track its movement. If there is a leak in the pipe, the sodium-24 will accumulate at the point of leakage and be detected, allowing the exact location of the leak to be identified.
Explain why the relative mass of an electron is considered negligible in calculating the relative atomic mass of an atom.
The mass of an electron is very small compared to the mass of a proton or a neutron (approximately 1/1840th the mass of either). When we are calculating the relative atomic mass of an atom, which is primarily the mass of the nucleus, the mass of the electrons is negligible. Therefore, the mass of the electrons is often ignored when computing the relative atomic mass.
Explain how the abundance of isotopes is used to calculate the relative atomic mass of an element.
The relative atomic mass is the weighted average of isotopic masses, and this is determined by the abundance of each isotope. The isotopes that occur more often will contribute more to the relative atomic mass than the less common isotopes. Therefore, the relative abundance of an isotope directly influences its contribution to the average mass of the element.
Explain how the understanding of isotopes helps to develop the field of nuclear medicine.
Isotopes are fundamental in the field of nuclear medicine. Specific radioisotopes are used for both diagnostic and therapeutic purposes because they emit radiation that can be used to detect and treat diseases. The properties of these isotopes, including their half-lives and types of radiation they emit, are taken into consideration to make them most effective and safe. The knowledge of isotopes has been used to develop techniques such as PET scans, radioactive tracers, and radiotherapies, making them a vital part of medical science.