Atoms and Nuclei
What are nucleons?
Neutrons and protons. They have approximately the same mass (10^-27 kg). Protons have a charge, while neutrons do not.
What are the 4 fundamental forces? List in ascending order of strength
Gravitational, Weak, Electromagnetic, Strong
What are the 4 types of radioactive decay?
Alpha decay, beta decay, gamma decay, spontaneous fission
What is deuterium? What is tritium?
Deuterium: a hydrogen nucleus with an extra neutron; total: 1 proton, 1 neutron
Tritium: a hydrogen nucleus with two extra neutrons; total: 1 proton, 2 neutrons
Which uranium isotope is naturally most abundant?
U-238
What is a gamma particle?
A photon with wavelength less than .01 nanometers
Which force is responsible for radioactive decay?
The weak force
How can we predict the exact moment a nuclide will decay?
We can't; radioactive decays are probabilistic
Who was the first scientist to understand the physics of nuclear fission?
Lise Meitner
Which uranium and plutonium isotopes can be used for nuclear weapons?
U-235 and Pu-239
What is an isotope?
Nuclides that have the same number of protons, but different numbers of neutrons
What element is the most stable/has the highest binding energy?
Iron-56
What is spontaneous fission?
When an isolated nucleus splits into two smaller nuclei, typically emitting a few neutrons
How can different isotopes (ex: U-235 and U-238) be chemically separated?
They can't
Does a fission bomb primarily use heavy or light elements? How about a fusion bomb?
Fission bombs primarily use heavy elements, while fusion bombs primarily use light elements.
How does the mass of an electron compare to the mass of a nucleon?
One nucleon is approximately 2000 times the mass of one electron.
How do the strengths of atomic binding energies compare to nuclear binding energies?
Nuclear binding energies are about 1 million times larger than atomic binding energies
What is the difference between alpha decay, beta decay, and gamma decay?
alpha decay emits an alpha particle (Helium-4), beta decay emits either an electron and anti-neutrino or anti-electron/positron and neutrino (electrons and positrons are known as beta particles), and gamma decay emits a gamma ray
How does fusion work?
Two nuclei combine to form a heavier nucleus, releasing energy in the process
What is the Doomsday Clock currently set to? Give three reasons why
85 seconds to midnight; accelerating great power competition and the rise of autocracy are undermining global cooperation, increasing the risk of nuclear war, misuse of biotechnology, artificial intelligence, and climate change
What does A = Z + N mean?
The atomic weight of a nucleus is equal to the number of protons + the number of neutrons. Z is called the "proton number" or "atomic number" while N is called the "neutron number"
What are the 2 competing forces within a nucleus? These forces determine the nuclear binding energy. Why is nuclear binding energy important?
Strong force: attractive force between nucleons
Electromagnetic force: repulsive force between protons
Nuclear binding energy is the source of nuclear energy used in nuclear reactors and released in nuclear bomb explosions
How can radioactive decay increase the number of protons (Z) in the nucleus? Can radioactive decay decrease the number of protons in the nucleus?
Negative beta decay increases Z by emitting an electron (a beta particle), which changes a proton into a neutron. Positive beta decay can decrease Z by emitting a positron, which change a neutron into a proton. Conservation of energy is maintained through the emission of a neutrino/anti-neutrino.
How does induced fission work?
What are three reasons why it is important to understand the physics of nuclear weapons?
1. How easy/difficult is it to develop a nuclear weapon?
2. Is it significantly more difficult to develop a hydrogen bomb vs a fission bomb?
3. What are the costs of modernizing nuclear arsenals?
4. What are the costs and benefits of weapon testing?
5. What are the status and cost for missile defense programs?
6. Etc.