Chemistry Study Material

Which of the following shows the masses of the three elementary particles in decreasing order? A. Leptons, Baryons, Mesons B. Mesons, Baryons, Leptons C. Baryons, Mesons, Leptons D. Leptons, Mesons Baryons Answer: Option C Nuclear fusion  and  nuclear fission  are different types of reactions that release energy due to the presence of high-powered  atomic bonds  between particles found within a nucleus. In fission, an atom is split into two or more smaller, lighter atoms. Fusion, in contrast, occurs when two or more smaller atoms fuse together, creating a larger, heavier atom. Definitions Fusion of deuterium with tritium creating helium-4, freeing a neutron, and releasing 17.59 MeV of energy. Nuclear fusion is the reaction in which two or more nuclei combine, forming a new  element  with a higher  atomic number (more protons in the

A half-life usually describes the decay of discrete entities, such as radioactive atoms. In that case, it does not work to use the definition that states "half-life is the time required for exactly half of the entities to decay". For example, if there is just one radioactive atom, and its half-life is one second, there will  not  be "half of an atom" left after one second. An exponential decay can be described by any of the following three equivalent formulas: {\displaystyle {\begin{aligned}N(t)&=N_{0}\left({\frac {1}{2}}\right)^{\frac {t}{t_{1/2}}}\\N(t)&=N_{0}e^{-{\frac {t}{\tau }}}\\N(t)&=N_{0}e^{-\lambda t}\end{aligned}}} where N 0  is the initial quantity of the substance that will decay (this quantity may be measured in grams, moles, number of atoms, etc.), N ( t ) is the quantity that still remains and has not yet decayed after a time  t , t 1⁄2  is the half-life of the decaying quantity, τ  is a  positive number  called the  mean

Certain naturally occurring radioactive isotopes are unstable: Their nucleus breaks apart, undergoing nuclear decay. Sometimes the product of that nuclear decay is unstable itself and undergoes nuclear decay, too. For example, when U-238 (one of the radioactive isotopes of uranium) initially decays, it produces Th-234, which decays to Pa-234. The decay continues until, finally, after a total of 14 steps, Pb-206 is produced. Pb-206 is stable, and the decay sequence, or series, stops. All elements with 84 or more protons are unstable; they eventually undergo decay. Other isotopes with fewer protons in their nucleus are also radioactive. The radioactivity corresponds to the neutron/proton ratio in the atom: If the neutron/proton ratio is too high (there are too many neutrons or too few protons), the isotope is said to be  neutron rich  and is, therefore, unstable. If the neutron/proton ratio is too low (there are too few neutrons or too many protons), the isotope is unstab

Radioactivity is spontaneous and random?    A.True    B.False Answer : True Radioactivity is the phenomenon exhibited by the nuclei of an atom as a result of nuclear instability. It is a process by which the nucleus of an unstable atom loses energy by emitting radiation. Radioactivity was discovered by Henry Becquerel completely by accident. He wrapped a sample of a Uranium compound in a black paper and put it in a drawer that contained photographic plates. On examining these plates later, he found that they had already been exposed. This phenomenon was termed as  Radioactive Decay . The element or isotope which emits radiation and undergoes the process of radioactivity is called  Radioactive Element . The radioisotope of an element has unstable nuclei and thus do not have sufficient binding energy to hold all the particles of an atom. To stabilize, these isotopes constantly decay. In this entire process of radioactive decay, they release a lot of energy in the form of  radia