Unit 5 - Nuclear physics Flashcards
What is a Cathode Ray Tube
Spits out electrons
Alpha particles
Positively charged particle that consists of 3 protons and 2 neutrons bound together
Who revealed the structure of atom with his gold foil experiment and what exactly was the experiment
Rutherford
A thing beam of alpha particles was made to strike against a gold foil and he noticed that some particles faced larger deviation from their original line of motion
Why did rutherford use gold for his experiment to discover structure of atom
Extremely malleable and ductile and the effect is more permanent on gold
conclusions from rutherford’s experiment and why?
Most of the space in an atom is empty as majority of the α particles passed through without major deviation
The entire +ve charge of the atom is placed in the centre in the nucleus as some α particles faced strong repulsive force from the nucleus causing them to deviate from original trajectory.
The mass of an atom is also concentrated in the centre
Electrons orbit around the nucleus in a circular order
Atomic number and what is represented with?
The number of protons present within the nucleus of an atom.
Rep using Z
Neutron number and what is represented with?
Total number of neutrons present in the nucleus
Rep using N
Mass no. and what is represented with?
Total number of nucleons (protons + neutrons) present within the nucleus
Rep using A
Relationship between mass no, atomic number, neutron number
A = Z + N
Anti protons
Subatomic particle that is the anti matter counter part of a proton and has the same mass as protons. Negatively charged
Isotopes
Nuclei of the same element having same atomic number but different mass number. They have the same number of protons but different number of neutrons
Thermal Neutron
A neutron with very less energy and has gained it through heating it
Specialty of Uranium in terms of its uniqueness
the only naturally occurring radioactive element
Why are nuclei also unstable like atoms
Because there are multiple positively charged protons repelling each other, hence there is a very strong unstable repulsive force present within the nucleus of an atom
What takes place in a nucleus to give it 1000 N force
Protons repel each other, and due to the presence of a strong nuclear force they are held in place as well
Strong Nuclear Force
Force present within the nucleus
Attracts protons and neutrons
Responsible for protons not scattering
Relationship between strong nuclear force and repulsive force in a nucleus
Both are present and are as strong as they should be, however, strong nuclear froce is more than repulsive force
Radioactivity
The process in which an unstable nucleus undergoes to attain stability and release energy
Alpha Decay
Type of radioactive decay where an unstable nucleus decays to give out a more stable nucleus with -4 in mass number and -2 in atomic number alongside an Helium atom with 4 mass number and 2 atomic number
Beta Decay
Type of radioactive decay where an unstable nucleus decays to give out a more stable nucleus with a +1 in atomic number, -1 in neutron number while the mass number remains the same. It also emits a an beta minus particle with an anti-neutrino particle
Why is the mass number same in beta decay
Because one proton is added and one neutron is removed
Why is there one neutron less in beta decay in the daughter nucleus
Because one neutron decays to give out a proton, beta minus particle and anti neutrino
Beta minus particle atomic and mass number
Mass number = 0
Atomic number = -1
Anti neutrino represnetation
Mass number = 0
Atomic number = 0
Written as a V with a bar on top ( ̅ν)
Gamma Decay
A type of radioactive decay which generally happens after an alpha or beta decay (but can occur on its own as well), in which a unstable nucleus decays to give the nucleus (same isotope) but with an neutrino particle as well
Neutrino particle representaion
Rep using V
Mass number = 0
Atomic number = 0
How to symbolize less stable nucleus in gamma decay
By putting an asterisk sign (*)
Law of radioactive decay
The number of unstable nuclei undergoing a decay per unit time is directly proportional to the number of undecayed nuclei
How does the graph of law of radioactive decay look like
Exponentially decaying asymptote curve
Formula for law of radioactive decay and significance of negative sign
ΔN/Δt ∝ -N
N = number of undecayed nuclei
The negative sign is used to indicate that the number of undecayed nuclei will decrease over time
Properties of Radioactivity
1) It is spontaneous reaction
2) It is a random process
Half Life
Time elapsed for half of the unstable nuclei to undergo decay
Represented using T_1/2
What to do if you get decimal nuclei while half life-ing a set number of nuclei
Round the nuclei to one whole number below as decimal nuclei cant exist
Formula for number of unstable nuclei after t units of time has elapsed
N = (1/2)^(t/half life) * N_0
N_0 = number of initial unstable nuclei
Factors affecting number of undecayed nuclei
Initial number of undecayed nuclei (Higher the number of N_0, higher the rate of reaction)
Type of isotope (basically half life)
Is Fission and Fusion spontaneous
No, requires intervention
Fission and which isotopes can undergo it
One big unstable nucleus breaks down into 2 smaller nuclei
Only Uranium 235 and Plutonium 239
How does fission happen
A neutron is shot into U-235 with that much energy so that it penetrates the nucleus and STAYS THERE. This causes U-235 to become U-236 and then it undergoes fission to give out 2 more stable nuclei (generally Barium and Krypton) with neutrons.
Can the neutrons given out after fission be used directly?
No, their energy is too high and we need to bring it down using a Moderator
Moderator in Fission/Fusion
Substance used to bring down the energy of neutrons given out in the fission reaction so that they can be re-used. Generally the material used is Heavy Water
Chain Reaction
Multiple fissions taking place one after the other and reusing the neutrons given out to create high amounts of energy.
Uncontrolled Chain reaction
High amount of energy is produced in short period of time with a huge number of uncontrolled fissions. With each fission occurring, the neutrons produced add more fissions and hence increases exponentially. Used in Atom Bomb
Controlled chain reaction
Happens if you are able to control the energy given out using Control rods. Happnes in Nuclear power plant
What are control rods made of and why
Cadmium, because they can absorb neutrons without undergoing fission. Control rods also allow for the energy produced to be used efficiently
Fusion
2 or more smaller nuclei combine together to form a bigger more stable nuclei
Why cant fusion take place without fission on earth
Because 2 positively charged neutrons are trying to fuse together, we need a great amount of energy to outweigh the repulsive force and hence it required a very high temperature
Temperature required for fusion to take place
10^7 Kelvin
Which releases more energy, fusion or fission
Fusion
Is mass conserved in fission/fussion
No, mass of reactants is more than mass of products and the mass lost is given out in the form of energy
Bomb made with Fusion is known as
Hydrogen bomb, required an atomic bomb first to achieve 10^7 K temp and then only will an Hydrogen bomb work
Which is more destructive and why, hydrogen bomb or atomic bomb
Hydrogen bomb, as energy release is more
Is fission better or fusion
Fusion is better as produces more energy, doesn’t produce long term radioactivity and has unlimited fuel supply. Fusion also produces more stable nuclei than fission
Mass and atomic number of Krypton
92 = Mass number
36 = Atomic number
Mass and atomic number of Barium
141 = Mass number
56 = Atomic number
Detecting radiation and background radiation
To detetct radiation, we can use a Geiger Muller Tube which sends a signal to its counter whenever it absorbs radiation. The closer to the source, higher and more accurate the readings will be.
To detetct bg radiation, we use Geiger muller tube and without any source, see the reading it shows, thats the bg radiation.
