# Isotopes ## Isotopes

Define the term ‘isotope’:

Isotopes are atoms of the same element with the same atomic number but a different atomic mass due to a change in the number of neutrons.

Outline examples & uses of isotopes:

Some famous examples of isotopes are the Hydrogen isotopes – Hydrogen-1 (Protium), Hydrogen-2 (Deuterium), and Hydrogen-1 (Tritium). The number after the element is the atomic mass.

• Hydrogen-1 is used to make ammonia with nitrogen and is used to turn unsaturated or liquid fats into solid fats for food and soaps
• Hydrogen-2 is mainly used to produce hydrogen bombs
• Hydrogen-3 is used in nuclear fusion reactions and can be possibly used as an artificial radioactive tracer

Define Relative Atomic Mass:

Relative atomic mass is the relative average of the atomic mass of an element based on the abundances of its isotopes

Define Isotope Abundance:

Isotopic abundance refers to how much of a given element is a particular isotope

Calculate the relative atomic mass of elements using the percentage abundance of their isotopes

The relative atomic mass of an element is calculated by multiplying and adding the abundance and mass of all the isotopes of an element and then dividing by 100.

Example of Calculating Relative Atomic Mass:

For example, Copper has two naturally occurring isotopes, which are Copper-63 and Copper-64. Copper-63 has a mass of 62.93amu (atomic mass unit) and an isotopic abundance of 69.2%. Copper-65 has a mass of 64.94amu and an isotopic abundance of 30.8%

Write Isotopes using the correct notation:

• To write an isotope normally, the correct notation is to write the element’s name alongside the atomic mass of the isotope rounded to the nearest amu. (e.g. Uranium-235)
• To write an isotope in the scientific notation, the correct notation is to write the Element’s symbol, and to its left, in a superscript, you write the element’s mass number (protons + neutrons), and on its left, in a subscript, you write the number of protons.

Compare Stable and Unstable Nuclei

Stable Nuclei:

• Stable nuclei have a balanced number of protons and neutrons
• Elements with naturally stable nuclei are located in the lighter section of the periodic table.
• All nuclei with proton numbers under 83 are naturally stable

Unstable Nuclei:

• Unstable nuclei have an unbalanced number of protons and neutrons, too much of either.
• Unstable nuclei are generally heavy due to an excess number of protons and neutrons. Because of this they decay and emit particles in order to achieve a balanced state.
• All nuclei with proton numbers over 83 are unstable and radioactive.

Define Parent Isotope and Daughter Isotope:

Parent Isotope:

This is the radioactive isotope that occurs before decay starts to take place.

(e.g. Uranium-238)

Daughter Isotope:

This is the radioactive isotope that comes as a product of decay.

(e.g. Lead-206 is a daughter isotope of Uranium-238)

Define the terms ‘decay series’, ‘parent isotope’, ‘daughter isotope’, ‘half-life’ and ‘transuranium element’:

Decay Series:

This is defined as the series of decay in which a radioactive element is decomposed into different elements until it produces one stable atom. The decay series involves alpha and beta decay until a stable atom is formed from a radioactive isotope.

(e.g. Uranium-238 decays to form Lead-206)

Parent Isotope:

This is the radioactive isotope that occurs before decay starts to take place.

(e.g. Uranium-238)

Daughter Isotope:

This is the radioactive isotope that comes as a product of decay.

(e.g. Lead-206 is a daughter isotope of Uranium-238)

Half Life:

The Half Life of a substance is the time required for something to reduce to half its original value

(e.g. the Half Life of Uranium-238 is 4.8 Billion years)

Transuranium Elements:

These are the elements that have radioactive isotopes that decay to form stable atoms. The term ‘transuranium’ is used to signify that these elements have an atomic number greater than 92, which is the atomic number of Uranium.

(e.g. Uranium)

Define Alpha, Beta, and Gamma Decay:

Alpha Decay:

This is a type of decay in which 2 protons and neutrons are emitted. This is usually represented as Helium-2. Alpha particles have a charge of +2

Beta Decay:

This is a type of decay in which a neutron transforms into a proton and electron. This is usually represented with the lowercase e (symbolizing an electron) accompanied by the Beta symbol (β) in the atomic mass section in an isotope’s notation. Beta particles have a charge of -1

Gamma Decay:

This is a type of decay in which gamma rays are emitted. Gamma decay usually occurs after alpha or beta decay. This is usually represented by putting an asterisk on the isotope on the left side of the equation (symbolizing excess energy), and adding the gamma symbol (γ) on the right side. Gamma rays have a charge of 0.

Compare Alpha, Beta, and Gamma Decay:

Solve Questions with Alpha, Beta and Gamma Decay:

Alpha Decay Question:

• First, identify the question:
“Alpha decay of Americium-243”

• Identify the atomic number of Americium and write down the full isotope

• On the right side, write an isotope with an atomic number of 2 and an atomic mass of 4. Make the base atom as the Alpha symbol (α)

• Add a new isotope. The mass number should be a subtraction of the alpha particle from the Isotope on the left. The atomic number should be the same. Identify the atom for the new isotope.

Beta Decay Question:

• First, identify the question:
“Beta decay of Cesium-137”

• Identify the Atomic Number of Cesium and write down the full isotope in the right format
• On the right side, add the beta particle. This is done by making the base atom ‘e’ for Electron, make the atomic number as -1 (to represent the charge) and make the atomic mass as β (to represent the beta particle
• Add a new isotope on the right with the same atomic mass of the isotope on the left and add 1 to the atomic number. Identify the atom.

Gamma Decay Question:

• First, identify the question:
“Beta decay of Boron-12 followed by gamma decay”

• Identify the equation for beta decay (see the steps above)
• Next, in a new equation, place the Carbon-12 on the right side of the equation and put an asterisk next to the Isotope
• Next, on the right side of the equation, put the exact same Carbon-12 isotope without the asterisk, and add the gamma symbol

Because the question asked for both beta decay and gamma decay, ensure you keep the beta decay equation in your answer along with the gamma decay equation below it in the form of steps to show the sequence ​

Define Geiger Counters:

Geiger counters are devices used to detect radioactive emissions in industries where radioactive elements are used. Geiger counters can detect all types of radiation but are most commonly used to detect beta and gamma radiation.

Outline how a Geiger counter Functions:

Geiger counters work using inert gases that become unnaturally conductive of electricity when impacted by high-energy particles or radiation