Atomic Nucleus

nucleon

protons and neutrons

beta decay

radioactive decay in which an electron is emitted; β- decay and β+ decay

atomic mass

The average mass of all the isotopes of an element

alpha decay

A nuclear reaction in which an atom emits an alpha particle consisting of two protons and two neutrons. This decreases the atomic number by 2 and the mass number by 4. Ex: ²³⁸₉₂U →⁴₂He + ²³⁴₉₀Th

When a nucleus undergoes ordinary fission into two daughter nuclei, what happens to the binding energy of the parent nucleus? A. It partly becomes the kinetic energy of the daughter nuclei B. It is released as a high-energy photon C. It is fully transferred to the binding energy of the daughter nuclei. D. It is transferred into the excited energy levels of the daughter nuclei

A. It partly becomes the kinetic energy of the daughter nuclei In ordinary fission, gamma ray photons are not emitted by a decaying nucleus. During ordinary fission, the electronic energy levels do not strongly play a role in the decay process. In ordinary fission, the binding energy of the parent nucleus is transformed into the kinetic energy of the daughter nuclei.

Which of the following isotopes is the most likely X in the reaction ²³⁶₉₂U→⁹²₃₆Kr + 3n + X, where n denotes a free neutron? A. ¹⁴¹₅₆Ba B. ¹⁴³₅₇ La C. ¹⁴²₅₇ La D. ¹⁴²₅₆ Ba

A. ¹⁴¹₅₆Ba

If there is 10 kg of a radioactive isotope with decay rate 0.1, 1/s, how much of the isotope will be left in 30 s? A. 0 kg B. 0.5 kg C. 5 kg D. 9 kg

B. 0.5 kg N(t)=No*e^-kt N(t) = 10*e^-.1*30 N(t) = 10e^-3 0.5 kg

Suppose 64 atoms of a highly unstable Polonium isotope (half-life 10 seconds) are held in a closed container. Which of the following provides the best estimate of when there will no longer be any of the Polonium isotope left in the container? A. 60 s B. 70 s C. There is always some isotope remaining D. 30 s

B. 70 s After 101010 seconds, there are, on average, only 32 atoms. Repeating this division (or observing that 2^6 = 64) it is apparent that we would only expect there to be one atom after 10*6 = 60 s Thus after an additional 10 seconds (a total of 7 half-lives) we would expect there to be only half an atom; because we can't have half an atom we would estimate there to be none of the isotope left at this time

Suppose that, in a mass spectrometer, charged isotopes enter the device with velocities along a direction that is neither perpendicular nor parallel to the magnetic field lines. Which of the following behaviors would result? A. the isotopes would travel in elliptical orbits B. the isotopes would travel in a corkscrew pattern C. the isotopes would not be deflected D. the isotopes would commence uniform circular motion

B. the isotopes would travel in a corkscrew pattern

Which of the following will be a decay product when ²³₁₂Mg undergoes beta minus decay? A. ²⁴₁₄Si B. ²³₁₃Al C. ²⁴₁₂Mg D. ²²₁₂Mg

B. ²³₁₃Al

Which of the following pairs of charged isotopes would be impossible to distinguish using a standard mass spectrometer? A. ¹²₁₁Na⁺ and ¹²₁₂Mg²⁺ B. ¹²₁₁Na⁺ and ¹⁴₁₁Na⁺ C. ¹²₁₁Na⁺ and ²⁴₂₀Ca²⁺ D. ¹²₁₁Na⁺ and ⁶₃Li⁺

C. ¹²₁₁Na⁺ and ²⁴₂₀Ca² this pair are impossible to distinguish because they have the same charge-to-mass ratio

Suppose that natural nitrogen is found in 70% abundance as the isotope ¹⁴₇N and the rest of the time as ¹²₇N. In this scenario, which of the following would give the atomic mass of this element? A. 13 amu B. 12.6 amu C. 14 amu D. 13.4 amu

D. 13.4 amu

Which of the following decay processes results in the largest change in mass of a nucleus? A. beta decay B. gamma decay C. neutron emission D. alpha decay

D. alpha decay

fission

The splitting of an atomic nucleus to release energy.

β- decay

a neutron in an atom changes into a proton, an electron, and an antineutrino, creating and releasing an electron along the way; mass number stays the same and atomic number increases by 1 ex: ²³⁴₉₀Th → ⁰−₁β + ²³⁴₉₁Pa

β+ decay

a proton turns into a neutron, causing the nucleus to shoot out a positron, or anti-electron; mass number stays the same and atomic number decreases by 1 ex: ²³⁴₉₀Th → ⁰₊₁β + ²³⁴₈₉Ac

gamma decay

the release of gamma rays from a nucleus; the same element goes from excited state to ground state, no numbers change Ex: ⁹⁹₄₃Tc → ⁰₀γ + ⁹⁹₄₃Tc