CBSE Class 12 (Science) Nuclei — practice questions
81 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice CBSE Class 12 (Science) Nuclei in the app →The unified atomic mass unit (u) is defined as exactly $1/12$ of the mass of an atom of which isotope?The mass defect $\Delta m$ of a nucleus $\,^{A}_{Z}\mathrm{X}$ with mass $M$ is defined asThe energy equivalent of one unified atomic mass unit (1 u) is closest toWhen a nucleus $\,^{A}_{Z}\mathrm{X}$ undergoes ALPHA decay, the daughter nucleus hasIn BETA-MINUS ($\beta^-$) decay, the parent nucleus emits an electron AND another particle. The other particleA radioactive sample has half-life $T_{1/2} = 5$ years. Starting with $N_0$ undecayed nuclei, the number remaiThe total binding energy of $\,^{16}_{8}\mathrm{O}$ is approximately $127.6\,\text{MeV}$. Its binding energy pOne atomic mass unit is equal to about how many kilograms?What is the mass of a proton in atomic mass units?A free neutron decays into a proton, an electron and which particle?In 1932 Chadwick bombarded which nuclei with alpha particles?Chadwick won the 1935 Nobel Prize in Physics for discovering what?What common term covers both protons and neutrons in a nucleus?Nuclei with the same mass number A but different Z are called what?198Hg (Z = 80) and 197Au (Z = 79) are an example of which pair?How many neutrons are in a nucleus of gold-197 (Z = 79)?Why do isotopes of an element behave identically in chemical reactions?A deuterium nucleus contains how many protons and neutrons?Chlorine has isotopes of 34.98 u (75.4 percent) and 36.98 u (24.6 percent). What is its average atomic mass?How does nuclear radius R depend on mass number A?Taking R0 = 1.2 fm, what is the radius of a nucleus with A = 27?Nucleus X has A = 125 and nucleus Y has A = 8. What is the ratio of radius X to radius Y?Nuclear matter has a density of roughly how many kg per cubic metre?Nuclear matter is denser than water by roughly what factor?A 5.5 MeV alpha particle comes within about what distance of a gold nucleus?Why do very fast alpha particles deviate from Rutherford scattering?Accurate nuclear sizes were measured by scattering which projectiles?How much energy is released if 1 g of matter is fully converted to energy?A nucleus has a mass defect of 0.02 u. What binding energy does it have?Oxygen-16 has a mass defect of 0.13691 u. What is its binding energy?Oxygen-16 has a total binding energy of 127.5 MeV. What is it per nucleon?How does a nucleus's mass compare with the sum of its free nucleons?The energy needed to split a nucleus into its nucleons is called what?Binding energy per nucleon equals the binding energy divided by what?The binding energy per nucleon curve peaks near which mass number?What is the peak binding energy per nucleon on the curve?The binding energy per nucleon of a nucleus with A = 238 is about what?For which range of A is binding energy per nucleon nearly constant?Constant binding energy per nucleon indicates the nuclear force is what?Binding energy per nucleon is below 8.0 MeV for which nuclei?Among nuclear, Coulomb and gravitational forces, which is the weakest?Beyond what separation does the nuclear force fall to nearly zero?The nuclear force between two nucleons is attractive beyond roughly what separation?How does the nuclear force between two protons compare with that between two neutrons?Becquerel found a wrapped photographic plate blackened by which salts?Which decay emits electrons or positrons from the nucleus?Gamma decay involves emission of what?Electric and magnetic fields showed gamma rays to be what?Alpha particles were proved to be what?What is the SI unit of radioactive activity?One becquerel corresponds to how many decays?One curie equals how many becquerels?Half-life is the time in which a sample's activity falls to what fraction?A sample has 80 g of a nuclide with half-life 2 days. How much remains after 6 days?Activity falls from 800 Bq to 100 Bq in 9 days. What is the half-life?At the level of single atoms, radioactive decay is what kind of process?Which force is responsible for beta decay?In electron capture, a proton-rich nucleus captures what?Which two new elements did the Curies isolate from uranium ores?Rutherford and Soddy realised that decay processes resulted in what?Fission of 1 kg of uranium releases about how much energy?Burning 1 kg of coal gives about 10⁷ J. Fission of 1 kg of uranium gives how many times more?Nuclear reaction energies are typically of the order of what?A neutron splits uranium-235 into two mid-mass fragments. What is this called?In n + U-235 → Ba-144 + Kr-89 + x neutrons, what is x?U-235 absorbs a neutron and splits into Xe-140, Sr-94 and x neutrons. Find x.Typical energy released per fissioning uranium nucleus is about what?A = 240 splits into two A = 120 nuclei; Ebn rises from 7.6 to 8.5 MeV. Energy gained?What do radioactive fission fragments emit to reach stable end products?When two light nuclei fuse into a heavier nucleus, what happens?In p + p → d + e⁺ + ν, how much energy is released?The Coulomb barrier between two protons is about how high?What is the approximate temperature of the Sun's interior?Fusion driven by raising the temperature is called what?The net result of the Sun's proton-proton cycle is four hydrogen forming what?How much energy is released when four hydrogen atoms fuse into helium?At about 10⁸ K, a star's core fuses helium nuclei into what?What will the Sun become after its core hydrogen is exhausted?Controlled fusion reactors aim to heat fuel to about what temperature?What is the main challenge in controlled thermonuclear fusion?The Sun is about 5 × 10⁹ years old. Its hydrogen should last about how much longer?