All exercise Short Questions of Basic Properties of Nucleus of book Nuclear Physics for BS/MSc Physics students.
Q.1 What are the constituents of nucleus?
Ans. The constituents of the atom are protons, neutrons and electrons. The protons and neutrons (nucleons) are found in the nucleus of atoms. The nucleus of an atom is surrounded by empty space in which there are electrons.
Q.2 What keeps a nucleus together?
Ans. The force that holds a nucleus together is the nuclear force, a short-range force between nucleons. At very small separations, the nuclear force is repulsive, keeping the protons and neutrons from getting too close to one another.
Q.3 What are the properties of nucleus?
Ans. Nucleus the central part of an atom contains almost entire mass of the atom consists of two principal elementary particles, namely, proton and neutron. Proton is a positively charged particle, while neutron has zero electrical charge.
Q.4 How is a nucleus, an atom Stabilized explain?
Ans. An atom is composed of a positively-charged nucleus, with a cloud of negatively-charged electrons surrounding it, bound together by electrostatic force. Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud.
Q.4 What is the radius of a nucleus?
Ans. Protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of1.75 fm(1.75×10 to the power of -15 m) for hydrogen (the diameter of a single proton) to about 15 fm for the heaviest atoms, such as uranium.
Q.5 What is a nucleus made of?
The atomic nucleus consists of nucleons—protons and neutrons. Protons and neutrons are made of quarks and held together by the strong force generated by gluon exchange between quarks.
Q.6 What are the 2 nuclear forces?
Nuclear forces (also known as nuclear interactions or strong forces) are the forces that act between two or more nucleons. They bind protons and neutrons (“nucleons”) into atomic nuclei. The nuclear force is about 10 million times stronger than the chemical binding that holds atoms together in molecules.
Q.7 What is the shape of the nucleus?
Ans. The deduced shape of the Radium-224 nucleus is that of a pear. This is news to scientists; while pear-shaped nuclei had been predicted by mathematical models, no one had ever directly observed one before. All previously measured atomic nuclei had been either spherical or had the rugby ball-like ellipsoidal shape.
Q.8 How the nucleus is stable?
It is the balance of protons and neutrons in a nucleus which determines whether a nucleus will be stable or unstable. Too many neutrons or protons upset this balance disrupting the binding energy from the strong nuclear forces making the nucleus unstable.
Q.9 What are the main elements of the nucleus?
Ans. The nucleus is a collection of particles called protons, which are positively charged, and neutrons, which are electrically neutral. Protons and neutrons are in turn made up of particles called quarks. The chemical element of an atom is determined by the number of protons, or the atomic number, Z, of the nucleus.
Q.10 Why are neutrons in the nucleus?
Ans. This is because protons have positive charges and the only reason that they are willing to stay together in the nucleus is because the neutrons effectively act as “filters” for these positive charges by interacting with the protons themselves.
Q.11 Why do electrons not fall into the nucleus?
Ans. Electrons are not little balls that can fall into the nucleus under electrostatic attraction. Rather, electrons are quantized wavefunctions that spread out in space and can sometimes act like particles in limited ways. An electron in an atom spreads out according to its energy.
Q.12 How was the nucleus discovered?
Ans. The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. … Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud.
Q.13 Why is the nucleus spherical?
Ans. Why is the nucleus of an atom spherical? Atoms are not spherical in shape. The liquid drop model for a nucleus assumes the nucleus to be spherical, that is approximation made to explain the binding energy of the nucleus and certain other properties like the criteria for nuclear fission to occur.
Q.14 Do electrons reside in the nucleus?
Ans. Electrons are the smallest of the three particles that make up atoms. Electrons are found in shells or orbitals that surround the nucleus of an atom. Protons and neutrons are found in the nucleus. They group together in the center of the atom.
Q.15 What is nucleus number?
Ans. The Nucleus. … The simplest nucleus is that of hydrogen, which is just a single proton, while the largest nucleus studied has nearly 300 nucleons. A nucleus is identified as in the example below by its atomic number Z (i.e., the number of protons), the neutron number, N, and the mass number, A, where A = Z + N.
Q.16 What is a isotope in science?
Ans. An isotope is a form of a chemical element whose atomic nucleus contains a specific number of neutron s, in addition to the number of proton s that uniquely defines the element. The nuclei of most atom s contain neutrons as well as protons.
Q.17 What makes electrons move around the nucleus?
Ans. Electrons were once thought to orbit a nucleus much as planets orbit the sun. … Like gravity acting on planets, an electromagnetic force attracts the orbiting electron to the nucleus. Classical physicists wondered that the electron didn’t run out of energy.
Q.18 How do electrons move around the nucleus?
Ans. Protons and neutrons make up the nucleus in the center of the atom. “Early on, we thought that electrons were revolving around the nucleus like planets,” Cooley said. … If you add energy, electrons can move to a higher orbital level and then back again when the energy returns to normal.
Q.19 How does an electron exist in the nucleus?
Ans. Orbital electrons DO NOT EXIST inside the nucleus. … An electron exists inside an atom only when and where allowed by its energy. The quantum energy of anelectron inside the atom forbids it from existing in it. Some say that the probability of an electron existing in a nucleus is zero.
Q.20 What is nucleus in nuclear physics?
Ans. A nucleus in nuclear physics refers to the nucleus of the atom. It usually consists of protons and neutrons, with the exception of Hydrogen-1, as it only has a single proton. Nuclei is the plural of nucleus which is a group of protons and neutrons at the middle of every atom.
Q.21 How do u find neutrons?
The mass number is the sum of protons and neutrons in the nucleus. The atomic number is the number of protons. Therefore, you can subtract the atomic number from the mass number to find the number of neutrons.
Q.22 What are 3 examples of isotopes?
Ans. Every chemical element is an isotope, and every element has at least two differentisotopes. Protium, deuterium, and tritium, for example, are all isotopes of hydrogen. Carbon has three isotopes, C-12, C-13, and C-14.
Q.23 How fast do electrons move around the nucleus?
Ans. A calculation shows that the electron is traveling at about 2,200 kilometers per second. That’s less than 1% of the speed of light, but it’s fast enough to get it around the Earth in just over 18 seconds.
Q.24 What is Nuclear Theory?
Ans. NUCLEAR THEORY. The process of nuclear fission can be understood on the basis of liquid drop model proposed by Yakov Frenkel, Neils Bohr and John Wheeler. … But the electrostatic force of repulsion is balanced by nuclear force of attraction between the constituents of the nucleus.
Q.25 Who is the father of nuclear physics?
Ans. Ernest Rutherford
was a New Zealand physicist who came to be known as the father of nuclear physics.
Q.26 What are properties of isotopes?
Ans. However they have different numbers of neutrons, which affects the mass number. Mass number determines the physical properties such as boiling/melting/density etc. They have similar chemical properties because isotopes of an element have the same number of electrons as an atom of that element.
Q.27 What is Isobar example?
Ans. Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons. Correspondingly, isobars differ in atomic number (or number of protons) but have the same mass number. An example of a series of isobars would be 40S, 40Cl, 40Ar, 40K, and 40Ca.
Q.28 How are isotopes created?
Ans. Isotopes are formed by changing the number of neutrons in an atom.
Q.29 What are Isotones give example?
Ans. Two nuclides are isotones if they have the same neutron number N, but different proton number Z. For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones. Similarly, 36S, 37Cl, 38Ar, 39K, and 40Ca nuclei are all isotones of 20 because they all contain 20 neutrons.
Q.30 Where do isotopes come from?
Ans. Where do isotopes come from? Long story short, isotopes are simply atoms with more neutrons — they were either formed that way, enriched with neutrons sometime during their life, or are originated from nuclear processes that alter atomic nuclei. So, they form like all other atoms.
Q.31 Do isobars have same physical properties?
Ans. Isobars indicate the relationship between different chemical elements but having the same atomic mass and thus the same physical properties.
Q.32 What is the difference between isobars and Isotones?
Ans. Isobars are the elements having same mass number but different atomic number. Isotones are the elements that are having the same number of neutrons. … Example: Oxygen and Carbon are different atoms but they have same number of neutrons i.e. 8 and different number of protons i.e. 8 and 6 respectively.
Q.33 What are the uses of isobars?
Ans. An isobar of cobalt is used in treatment of cancer. As the atomic no. of two isobars is different they have different chemical properties, Unlike isotopes, isobars do not have any significant application in chemistry. They are useful like U235 is used to determine the age of a planet etc.
Q.34 How many types of isotopes are there?
Ans. There are two main types of isotopes, and these are radioactive isotopes and stable isotopes. Stable isotopes have a stable combination of protons and neutrons, so they have stable nuclei and do not undergo decay.
Q.35 What is mass defect in physics?
Ans. Mass is associated with the binding energy between nucleons
In physics and chemistry, a mass defect refers to the difference in mass between an atom and the sum of the masses of the protons, neutrons, and electrons of the atom. … The “missing” mass is the energy released by the formation of the atomic nucleus.
Q.36 What is a mass defect and why is it important?
Ans. Nuclear binding energy is used to determine whether fission or fusion will be a favorable process. The mass defect of a nucleus represents the mass of the energy binding the nucleus, and is the difference between the mass of a nucleus and the sum of the masses of the nucleons of which it is composed.
Q.37 What is the cause of mass defect? (missing energy)
Ans. The actual mass is always less than the sum of the individual masses of the constituent protons and neutrons because energy is removed when when the nucleus is formed. … This mass, known as the mass defect, is missing in the resulting nucleus and represents the energy released when the nucleus is formed.
Q.38 What is mass deficit?
Ans. The mass deficit is defined as the amount of mass that was removed in creating the core. Mathematically, the mass deficit is defined as.
Q.39 How is mass defect determined?
Ans. The difference between the mass of a nucleus and the sum of the masses of the nucleons of which it is composed is called the mass defect. Three things need to be known in order to calculate the mass defect: … the composition of the nucleus (number of protons and of neutrons), the masses of a proton and of a neutron.
Q.40 Is mass defect positive or negative?
Ans. Usually the standard is that one mole of carbon-12 weighs exactly twelve grams, so that a bare proton or neutron has a positive mass defect, while a tightly-bound nucleus like iron or nickel has a negative mass defect. … The rest mass of a (simple or composite) particle is always well-defined
Q.41 What is the relationship between binding energy and mass defect?
Ans. Nuclear binding energy is the energy required to split an atom’s nucleus into protons and neutrons. Mass defect is the difference between the predicted mass and the actual mass of an atom’s nucleus. The binding energy of a system can appear as extra mass, which accounts for this difference. Created by Jay.
Q.42 What is nuclear mass?
Ans. Nuclear mass. The mass of an atomic nucleus, which is usually measured in atomic mass units; it is less than the sum of the masses of its constituent protons and neutrons by the binding energy of the nucleus divided by the square of the speed of light.
Q.43 Can binding energy be negative?
Ans. Since the mass of the nucleus is less than the mass of the protons and neutrons, the binding energy must be negative. … Binding energy is negative because if it was positive, or zero, then the nucleons would separate and escape into space.
Q.44 How do you calculate mass difference?
Ans. Divide Change in Mass by Initial Mass
Finally, you divide the change in mass by the initial mass of your substance. This calculation shows what proportion of the initial mass changed. To find the percent change, simply multiply this number by 100.
Q.45 What has a mass of 1 amu?
Ans. In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass. This is approximately 1.67377 x 10 -27 kilogram (kg), or 1.67377 x 10 -24gram (g). The mass of an atom in AMU is roughly equal to the sum of the number of protons and neutrons in the nucleus.
Q.46 Does a proton or neutron have more mass?
Ans. Protons and neutrons have approximately the same mass, but they are both much more massive than electrons (approximately 2,000 times as massive as an electron). The positive charge on a proton is equal in magnitude to the negative charge on an electron
Q.47 What is the binding energy of iron?
Ans. Iron-56 (56Fe) is the most common isotope of iron. About 91.754% of all iron is iron-56. Of all nuclides, iron-56 has the lowest mass per nucleon. With 8.8 MeV binding energy per nucleon, iron-56 is one of the most tightly bound nuclei.
Q.48 Which element has the largest binding energy?
Ans. Which element has the highest binding energy per nucleon. The graph of binding energy per nucleon seems to peak at Iron-56. However, Wikipedia says that Nickel-62 has the highest binding energy per nucleon of any known nuclide (8.7945 MeV)
Q.49 What is significance of binding energy per nucleon?
Ans. The decrease in the binding energy per nucleon at high mass numbers indicates that nucleons are more tightly bound when they are assembled into two middle mass nuclei than in single high mass nucleus. Therefore, energy can be released in nuclear fission of single massive nucleus into smaller fragments.
Q.50 What is electron binding energy?
Ans. Electron binding energy, also called ionization potential, is the energy required to remove an electron from an atom, a molecule, or an ion. In general, the binding energy of a single proton or neutron in a nucleus is approximately a million times greater than the binding energy of a single electron in an atom.
Q.51 Where does binding energy come from?
Ans. The binding energy inside an atomic nucleus (and in anything, really) comes fromthe mass of the objects being bound.
Q.51 Where does binding energy come from?
Ans. The binding energy inside an atomic nucleus (and in anything, really) comes fromthe mass of the objects being bound.
Q.51 How does binding energy work?
Ans. Work done to pull a nucleus apart into its constituent protons and neutrons increases the mass of the system. The work to disassemble the nucleus equals its binding energy BE. A bound system has less mass than the sum of its parts, especially noticeable in the nuclei, where forces and energies are very large.
Q.52 How do you find binding energy?
Ans. Once mass defect is known, nuclear binding energy can be calculated by converting that mass to energy by using E=mc2. Mass must be in units of kg. Once this energy, which is a quantity of joules for one nucleus, is known, it can be scaled into per-nucleon and per- mole quantities.
Q.53 Which element is the most stable energetically?
Ans. So, in one word, iron is quite stable. But, what about helium and other noble gases? They are considered the most stable elements in the whole periodic table. But their binding energy per nucleon value is less than iron-56.
Q.54 Why is lithium unstable?
Ans. Lithium is a relatively unstable element because its stable isotopes have a very low binding energy level. This means they are not prone to fission, which is breaking down. This is why, lithium is less common in the galaxy than some other elements with a higher atomic weight.
Q.55 Are atoms stable?
Ans. The nucleus of this kind of atom is said to be stable. In some atoms the binding energy is not strong enough to hold the nucleus together, and the nuclei of theseatoms are said to be unstable. Unstable atoms will lose neutrons and protons as they attempt to become stable.
Q.56 What is the significance of binding energy?
Ans. Nuclear binding energy is the energy required to split a nucleus of an atom into its component parts: protons and neutrons, or, collectively, the nucleons. The binding energy of nuclei is always a positive number, since all nuclei require net energy to separate them into individual protons and neutrons.
Q.57 How do you know if an atom is stable or unstable?
Ans. In summary it is the balance of protons and neutrons in a nucleus which determineswhether a nucleus will be stable or unstable. Too many neutrons or protons upset this balance disrupting the binding energy from the strong nuclear forces making the nucleus unstable.
Q.58 Does more stable mean less energy?
Ans. A molecule will be stable if there are more attractive forces and less repulsive forces. Attractive forces lower the potential energy of the molecule and repulsive forces increase the potential energy of the molecule. Therefore molecules with lower energy are more stable.
Q.59 What is the most unstable element?
Ans. Francium is a chemical element with the symbol Fr and atomic number 87. It used to be known as eka-caesium. It is extremely radioactive; its most stable isotope, francium-223 (originally called actinium K after the natural decay chain it appears in), has a half-life of only 22 minutes.
Q.60 Is lead the most stable element?
Ans. Some consider lead to be the most stable element of all because of its high atomic number. Lead has three stable isotopes and one unstable isotope. … The first isotope, Pb-204, is slightly radioactive and is considered primordial, meaning that it is older than the Earth itself. This is the unstable one
Q.61 What is the largest number of protons that can exist in a nucleus and still be stable?
Ans. Eventually, a point is reached beyond which there are no stable nuclei: the bismuthnucleus with 83 protons and 126 neutrons is the largest stable nucleus. Nucleiwith more than 83 protons are all unstable, and will eventually break up into smaller pieces; this is known as radioactivity.
Q.62 What is nuclear spin?
Ans. Nuclear Spin. It is common practice to represent the total angular momentum of a nucleus by the symbol I and to call it “nuclear spin”. … The half-integer spins of the odd-A nuclides suggests that this is the nuclear spin contributed by the odd neutron.
Q.63 Why do neutrons have magnetic dipole moments?
Ans. The neutron magnetic moment is the intrinsic magnetic dipole moment of theneutron, symbol μn. … The neutron has spin 1/2 ħ, but it has no net charge. The existence of the neutron’s magnetic moment was puzzling and defied a correct explanation until the quark model for particles was developed in the 1960s.
Q.64 Are protons magnetic?
Ans. Protons and neutrons, both nucleons, comprise the nucleus of an atom, and both nucleons act as small magnets whose strength is measured by their magneticmoments. The magnitude of the proton’s magnetic moment indicates that theproton is not an elementary particle.
Q.65 Give two examples of a nucleon.
Answer: Protons and neutrons are found in the nuclei of atoms and are therefore called nucleons.
Q.66 Give the atomic number of deuterium and tritium.
Answer: Deuterium and tritium are both isotopes of hydrogen. Deuterium has one proton and one neutron while tritium has one proton and two neutrons. They both have atomic number 1.
Q.67 How can the neutron have non zero magnetic moment?
Answer: As the neutron has net zero charge, it has an inner structure. The current view is that the neutron consists of three quarks of fractional charges. The charge distribution inside the neutron is thus not symmetrical, resulting in a nonzero magnetic moment.
Q.68 The nuclear radius is given by relation R = R0 = A1/3; how values of R0 differ for nuclear particles scattering on nuclei and for electron scattering on nuclei?
Answer: The value of R0 is given as;
R0 = 1.4F For nuclear particles scattering on nuclei
R0 = 1.2F For electrons scattering on nuclei
The difference between these two values can be explained as follows;
In electron scattering experiments, the location of positive charges associated with the protons in the nucleus is determined. In nuclear-particle scattering, the size of nuclear force producing region affecting the particle is determined. So the nuclear force extends beyond the region with which the charge or mass are associated , making the nucleus appear larger than actually it is . Thus value of R0 is greater for nuclear particles scattering on nuclei than for electrons scattering on nuclei.
Q.69 Differentiate between atom and nucleus with reference to size (length) and energy.
Answer: Nuclei , the bound states of nucleons, can be contrasted with atoms, the bound state of nuclei and electrons. The difference in the size and energy are;
| Quantity | Nucleus | Atom |
| Size | 10-15 m | 10-19 m |
| Energy | in MeV | in eV |
Q.70 What are the isotopes? What do they have in common and what are their differences?
Answer: Isotopes;
Isotopes are nuclei of same element have same charge (Z) but difference mass number (A).
Common and difference;
i. They have same number of protons but different number of neutrons.
ii. They have same chemical properties but different physical properties.
Q.71 Why are Heavy nuclei unstable?
Answer: Heavy nuclei having atomic number greater than 82 are mostly unstable. In heavy nuclei due to large number of protons and large electrostatic force of repulsion between them are unstable. Strong nuclear force can’t overcome repulsive forces.
Q.72 What is isospin? Explain in few lines.
Answer: For a given nucleus, the value of $T_z$ is just the minus one-half of the neutron excess.
$$T_Z=\frac{1}{2}\ (Z_N)$$
In a set of isobars of given A, a member X will have an isospin T_{z(max)}, largest among the set. For this,
$$T=T_{Z\left(max\right)}=\frac{1}{2}(Z_X-N_X) Having \left(2T+1\right)$$ states
The states are corresponding to different $T_Z$ and hence to different charges $\left(Z=\frac{A}{2}\pm1\right)$.
The isobars C14 , N14, O14 have $T_Z$ = -1,0,+1 respectively. The mirror nuclei H3 and He3 have $T= \frac{1}{2}$ in their ground state. Isospin assignments to excited nuclear levels can be established through reaction or scattering studies.
Q.71 What are assumptions of proton electron model?
Answer : The concept of proton- electron model of the nucleus arose from the following experimentally observed facts;
Some radioactive elements emitted β- rays which were found to be fast moving electrons
The discovery of isotopes and their whole number atomic weights suggested that all elements were built out of hydrogen atoms. The fractional atomic weights are due to the presence of two or more isotopes each of which has an integral mass,. The experimental results show that nuclei of different elements can be regarded as being a collection of an integral number of hydrogen nuclei. The nucleus of hydrogen has a positive charge equal in magnitude to that of the electron and is known as a proton.
Q.72 Distinguish between an isotope and an ion.
Answer: An isotope of an element has a different number of neutrons than a different isotopes of the same element . An ion is a charged atom. It is charged because it does not have the same number of protons as electrons.
Q.73 State the number of protons and neutrons in each of the following nuclei;
1H2, 6C12 , 26Fe56, 79Au197, and 38Sr90
Answer: Hydrogen 2 has 1 proton and 1 neutron. Carbon 12 has 6 protons and 6 neutrons. Iron 56 has 26 protons and 30 neutrons. Gold 197 has 79 protons and 118 neutrons. Strontium 90 has 38 protons and 52 neutrons.
Q.74 The observed spin of7 N14 is ђ . Show that it cannot be explained on the electron and proton model of the nucleus.
Answer : The proton as well as the electron is fermion having a spin ђ/2. The resultant spin angular momentum of the nucleus is given by the vector sum of the spins of all the particles in it. If the nucleus has even number of particles in it. If the nucleus has even number of particles it has an integral spin but if it has an odd number of particles then it has a half integral spin. According to electron – proton hypothesis , there should be 14 protons 7 electrons in it to give the nucleus a net positive charge of +7e. As the total number of particles is 14 + 7 + 21( an odd number) within the nucleus it should have half integral spin. But experimentally the spin is found to be ђ and not ђ/2 as required by the theory. Thus electron proton model cannot explain the spin of 7N14 to be equal to ђ.
Q.75 Most of the physical and chemical properties of an element are determined by the atomic number and arrangement of the electrons in its atoms (isotopes). Comment on this statement.
Answer: Since the isotopes of the element of have almost identical electron structures, the two isotopes of chlorine , for example , have the same yellow color, the safe suffocating smell, the same bleaching effect , and the same ability to combine chemically with metals. Because boiling and freezing points depend somewhat on atomic mass, these properties differ slightly between the isotopes, as does density.
Q.76 Find the value of quadruple moment of a system in which a proton is circling a spherical nucleus of equal values of Z and N.
Answer: As spheroid is having zero quadruple moment and < x2> = <y2> =< z2> = r2/3. As the proton is circling in xy plane, so change will be in xy plane or the distribution of charge is of oblate shape and thus the quadruple is negative.
