FUNPHYS 17 - Radioactivity & Medicine Flashcards
What is Electrostatic/Coulomb Repulsion?
Repulsion between the protons in the nucleus creating forces trying to pull the nucleus apart. Strong Nuclear Force counters it.
What is Strong Nuclear Force?
The forces that hold the nucleus together due to the nuclear attractive forces between two protons, two neutrons, or two nucleons. SNF if very short compared to Electrostatic forces and only works when two nucleons are at most 10^-15m away from each other.
What is nuclear stability dependent on?
Nuclear stability is dependent on the balance between Electrostatic forces and Strong Nuclear Forces. When the number of protons in nucleii increase, more neutrons are required for the shorter SNF to overcome the longer Electrostatic forces.
When does a nucleus disintegrate?
A nucleus disintegrates when the number of protons increases and the shorter SNF are insufficient enough to balance the longer EF forces between the protons.
What are the most stable nucleii with the largest number of protons?
Bismuth has 83 protons and the SNF can balance the Electrostatic forces. Any nucleii with more than 83 protons are unstable and will spontaneously disintegrate or rearrange their internal structure to gain stability.
What is Radioactivity?
The spontaneous disintegration or internal rearrangement of nucleii with more than 83 protons.
What happens when an unstable nucleus disintegrates?
It emits 3 types of high energy photons:
- a-particles
- b-particles
- gamma rays
Explain a-particles, a-decay, & transmutation
a-particles are very stable units consisting of 2 neutrons and 2 electrons. They can be ejected from an unstable nucleus, taking 2 neutrons and 2 electrons from the unstable nucleus for itself, and making the unstable nucleus into a new element. This is called Transmutation.
Explain b-particles.
b-particles are negatively charged and consist of an electron from an unstable nucleus and are much less massive than a-particles. They have a charge of 1.6 x 10^-19.
Explain b-minus decay & b-plus decay.
B-minus decay is when a neutron from an unstable nucleus decays into a proton (which stays with the unstable nucleus), an electron (the b-particle), and an antineutrino (massless and travel at the speed of light).
B-plus decay is when proton from an unstable nucleus decays into a neutron (which stays the unstable nucleus), a positron (the b-particle), and a neutrino.
Explain Electron Capture/K-capture.
An unstable nucleus brings an electron, from an orbital shell, into the nucleus and combines with a proton to form a neutron and neutrino (which is ejected).
Explain gamma rays.
Gamma rays are high energy photons that travel at the speed of light and can be calculated by E = hc/wavelength. Gamma rays form from the emission of high energy photons when an unstable nucleus goes from a high energy state to a lower energy state. This process doesn’t involve disintegration, so it’s not transmutation. The nucleus is just re-arranged.
Define Mass Deficit.
Stable nucleii have a nuclear mass that is less than the mass of their constituent parts. Mass deficit is the difference between the sum of the constituent parts and the mass of the original nucleus.
Define Binding Energy.
The energy required to break a nucleus into its constituent parts, therefore indicating how strongly a nucleus is held together. Calculated using E = mc^2
