Chemistry I - Atomic Mass and Exponential Decay
What is the charge of a beta decay particle and what is it most similar to?
-1 - It is most similar to an electron, which means it has a charge of -1 and a mass of ~0.0005.
What is the charge of a gamma decay particle?
0 - A gamma decay particle has no mass and no charge.
What is the weight of an amu
1 amu = 1.667x10^-27 kg
What are the three factors that can lead to stability of ions.
1) The number of protons found in the nucleus. 2) The number of neutrons found in the nucleus. 3) A 1:1 ratio of neutrons to protons
An isotope has the same __________ but a different __________ in their nuclei compared to the natural form of that element.
1. atomic number (protons) 2. Neutrons
How much of the original sample will remain after 3 half lives?
12.5%
How does eV compare to Joules?
1eV = 1.6x10^-19J
What does an alpha particle consist of?
2 protons and 2 neutrons
What is the charge of an alpha decay particle and what atom is it most similar to?
2+ - It is the same as a helium atom which has two protons and two neutrons.
How much of the original sample will remain after 4 half lives?
6.25%
Any atom with ___ protons or more will be unstable/radioactive.
83
What is the mass of an electron compared to protons or neutrons
An electron is about 0.05% of a proton or a neutron
What is the charge of a particle that is lost during positron emission?
+1 - The particle is very similar to that of an electron, only with a positive charge, this results in the loss of 1 positive charge from a particle.
Thorium (Th) has just undergone beta decay, how many protons and neutrons will remain?
- Beta decay does not affect the overall number of protons and neutrons so it will remain 232. - Beta decay increases the negative charge by 1, increasing the number of protons to 91. - This results in a Protactinium (Pa) isotope.
What happens to protons and neutrons when an atom undergoes beta decay?
- Decreases the number of neutrons and increases the number of protons by 1. - Does not decrease the mass number.
What happens to protons and neutrons when an atom undergoes alpha decay?
- Decreases the number of protons and neutrons by 2 - Decreases the mass number by 4
What happens to protons and neutrons when an atom undergoes gamma decay.
- Does not affect any of the numbers associated with an atom. - Removes an atom from its excited state to a relaxed state.
What happens to protons and neutrons when an atom undergoes electron capture.
- Increases the number of neutrons and decreases the number of protons by 1. - Does not affect the mass number.
What happens to protons and neutrons when an atom undergoes positron emission?
- Increases the number of neutrons and decreases the number of protons by 1. - Does not affect the mass number.
What is the mass defect of an atom.
- The mass defect is the difference between the predicted mass of an atom and the actual mass of an atom. - Mass defect is a value of mass that was converted to energy when the nucleus of the atom was formed.
What is an alpha particle most similar to?
A helium atom.
What is electron capture?
An atom will capture an electron and combines it with a proton to form a neutron.
What is atomic number and what is the symbol that denotes it?
Atomic number is equal to the number of protons in the nucleus of an atom. - Denoted as Z
What is the most common form of beta decay?
Beta decay that resembles an electron.
Calculate the binding energy of a Helium atom (He) with a mass defect of 0.0303766 amu.
E = M(C^2) E = (0.0303766 amu x (1.66054x10^-27 kg/1 amu)(C^2) E = 5.04417x10^29kg (2.99702 (speed of light))^2 E = 5.04417x10^29kg x 8.988x10^16m/s E = 4.533x10-6J
True or False: All atoms have an equal number of protons and electrons.
False. Atoms will tend to have different numbers of protons and electrons. - Neutrons are neutral atoms that have an equal number of protons and electrons and no charge.
What is given off after electron capture and how does this affect the number of protons or neutrons?
Gamma radiation and it does not affect the number of either.
What happens to the mass of an isotope compared to the natural form element?
It is different because the number of neutrons is different.
__________________ is the difference between the predicted mass of an atom and the actual mass of an atom.
Mass defect
What is the mass number of an element and how can it be found?
Mass number (A) is the sum of the number of protons and neutrons of an atom. - Can be calculated through the equation A = Z + N
What is the force that holds nucleons together?
Nuclear strong force
What are the two components of a nucleus?
Protons and neutrons (collectively neucleons)
How many protons, electrons, and neutrons are in the element: Uranium-235?
Protons: 92 Electrons: 92 Neutrons: 143
What is the consistent characteristic of beta decay?
The conversion of a neutron into a proton.
How could the binding energy of an atom be calculated?
With the Equation E = MC^2
Uranium undergoes positron emission, what is the result?
The loss of one proton and no change to the neutron, resulting in a Protactinium (Pa) isotope with 238 neucleons.
If an atom were to have one neutron added to it, how would the mass of the element change.
The newly formed isotope would have a mass that is approximately 1 amu greater than the natural element.
How can the energy needed to separate a nucleus be calculated?
The nuclear binding energy is the same regardless of binding molecular particles or separating.
If the nucleus of an atom cnsists of particles repelling each other how are they held together?
The nuclear strong force is stronger than the repulsive energy exerted between atomic particles.
Why are more neutrons required as the number of protons increases?
The number of increasing protons requires a greater nuclear strong force. This increase in required energy requires more neutrons to meet the neutron : proton ratio.
Unanium has undergone alpha decay, following this, how many protons and neutrons remain?
Uranium begins with 238 neucleons and 92 protons, following alpha decay, 234 nucleons, 144 neutrons, and 90 protons remain (Changes to Thorium)
What is the most simple and basic way to think about beta decay?
The number of protons will increase by 1 and the number of neutrons will decrease by 1, essentially 1 neutron will convert to a proton.
Potassium (K) undergoes electron capture, what is the result?
The original potassium would have 21 neutrons and 19 protons, the electron is captured and the number of protons is then 18, increasing the number of neutrons to 22.
A uranium particle has undergone gamma decay, what is the result?
The result will still be Uranium with 92 protons and 146 neutrons. The particle will simply just be placed into its ground state rather than excited state.
If a fluorine atom were to undergo positron emission, how would this affect the nucleus?
The resulting element would be an oxygen isotope with a mass number of 19, 11 neutrons and 8 protons.
What is the mass number of an atom and how can you solve for it?
The sum of the protons and neutrons in an atom. - Denoted as A - A = Z + N
What are the three types of beta decay?
electron emission ( traditional beta decay), positron emission, and electron capture.
When solving a mass-energy equivalence equation for MeV, what is the shortcut?
n amu x 931.5 MeV
The ______ is the nucleus that undergoes radioactive decay and the ______ is the resulting, more stable nucleus.
parent; daughter
Isotopes are two atoms of ______ element that _______ in the number of the neutrons they have.
same; differ
How is half life denoted?
t1/2
What is the atomic weight of an element?
weighted average of the masses of its naturally occurring isotopes of a given element.