1. THERE ARE NO ELECTRON INSIDE THE NUCLEI.
a) HOW CAN BETA PARTICLE OR AN ELECTRON COME FROM THE NUCLEUS
b) HOW CAN GAMA RAY IS EMITTED FROM A NUCLEUS
2. Q VALUE IS THE ENERGY CORRESPONDING TO THE DIFFERENCE IN MASS OF THE REACTANT NUCLEONS MINUS THE MASS OF THE PRODUCT NUCLEI.
a) IF Q VALUE IS POSITIVE,WHAT IS THE NATURE IS THE NUCLEAR REACTION.
b) IF Q VALUE IS NEGATIVE WHAT IS THE NATURE OF THE NUCLEAR REACTION
3. a) IF THE MASS OF THE PRODUCT NUCLEI IS <THE MASS OF THE REACTANT NUCLEI ,WHAT IS THE SIGN OF Q
b) IS ENERGY ISABSORBED OR RELEASED IN THE ABOVE CASE.
4. IF 1 Kg AND I Gm OF THE SAME RADIOACTIVE MATERIAL ARE TAKEN SEPARATELY.
a) WHAT IS THE MASS LEFT AFTER A HALFLIFE
b) WHAT IS THE MASS LEFT AFTER TWO HALF LIFE
5. a) IDENTIFY THE CHARGES ON RADIOACTIVE RAYS
b) COMPARE THE MASSES OF THE PARTICLES OF THE RADIOACTIVE RAYS
6. IT IS ESTIMATED THAT THE ENERGY RELEASED IN AN ATOM BOMB EXPLOSION HAS BEEN 7.6x10^13J. IF EACH FISSION RELEASES AN ENERGY OF 2000MeV,CALCULATE THE NUMBER OF ATOM FISSIONED
7. FIND THE ENERGY IN eV EQUIVLENT TO 1 a.m.u OF MATTER
8. WHICH ARE THE DIIFFERENT TYPES OF NUCLEAR REACTOR
9. WHAT ARE THE MAIN PARTS AND FUNCTION OF THE NUCLEAR REACTOR
10. a) WHAT IS HALF LIFE PERIOD
b) HALF LIFE OF A 3 ELEMENTS ARE GIVEN IN THE TABLE.RANK THE ELEMENTS ACCORDING TO THEIR ACTIVITIES
RADIUM - 1.6X10^3Y
LANTHUM - 1.1X10^10Y
PHOSPHOROUS - 14.3DAYS
11. CLASSIFY THE FOLLOWING STATEMENT AS PROPERTIES OF ALPHA PARTICLE AND BETA PARTICLE
PROPERTIES
a) THEY CAN INTERACT WITH ATOM AND AS A RESULT THEY GET SCATTERED WHILE TRAVELLING THROUGH MATTER.
b) WHILE COMING OUT FROM NUCLEUS THEY SOMETIMES INTERACT WITH ORBITAL ELECTRONS & THEY EJECT SECONDARY ELECTRON FROM ORBIT
c) THE ENERGY SPECTRUM APPEARS CONTINUOUS DUE TO THE CREATION OF VERY LIGHT PARTICLE CALLED NEUTRINO
d) THE VELOCITY & K.E OF PARTICLE DEPENDS ON ENERGY OF THE PARENT WHICH EMITS THEM
12. AN ATOMIC REACTOR IS YIELDING 30,000KW ENERGY PER SECOND. CALCULATE THE NUMBER OF URANIUM ATOM UNDERGO FISSION PER SECOND.GIVE THAT ENERGY PER FISSION IS 200 MeV.
Saturday, January 15, 2011
Wednesday, January 12, 2011
QUESTIONS
1.PREDICT THE CONSEQUENCE OF NUCLEAR FISSION.
2.WHY ARE THE CONTROL RODS MADE OF CADMIUM.
3. WHY HEAVY WATER IS USED AS A MODERATOR.
4.NUCLEAR FUSION IS CALLED THERMONUCLEAR REACTION WHY?
5.HOW IS ENERGY PRODUCED IN STARS.
6.WHAT IS THE ORDER OF TEMPERATURE FOR FUSION REACTION
2.WHY ARE THE CONTROL RODS MADE OF CADMIUM.
3. WHY HEAVY WATER IS USED AS A MODERATOR.
4.NUCLEAR FUSION IS CALLED THERMONUCLEAR REACTION WHY?
5.HOW IS ENERGY PRODUCED IN STARS.
6.WHAT IS THE ORDER OF TEMPERATURE FOR FUSION REACTION
DIFFERENCE BETWEEN FISSION AND FUSSION
Nuclear Fission vs Nuclear Fusion
Natural occurrence of the process:Fission reaction does not normally occur in nature.Fusion occurs in stars, such as the sun.
Byproducts of the reaction:Fission produces many highly radioactive particles.Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.
Energy Ratios:The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.The energy released by fusion is three to four times greater than the energy released by fission.
Nuclear weapon:One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to "trigger" a fusion reaction
Definition:Fission is the splitting of a large atom into two or more smaller ones.Fusion is the fusing of two or more lighter atoms into a larger one.
Conditions:Critical mass of the substance and high-speed neutrons are required.High density, high temperature environment is required.
Energy requirement:Takes little energy to split two atoms in a fission reaction.Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.
Natural occurrence of the process:Fission reaction does not normally occur in nature.Fusion occurs in stars, such as the sun.
Byproducts of the reaction:Fission produces many highly radioactive particles.Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.
Energy Ratios:The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.The energy released by fusion is three to four times greater than the energy released by fission.
Nuclear weapon:One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to "trigger" a fusion reaction
Definition:Fission is the splitting of a large atom into two or more smaller ones.Fusion is the fusing of two or more lighter atoms into a larger one.
Conditions:Critical mass of the substance and high-speed neutrons are required.High density, high temperature environment is required.
Energy requirement:Takes little energy to split two atoms in a fission reaction.Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.
NUCLEAR FUSION
The process in which two or more light nuclei are combined into a single nucleus with the release of tremendous amount of energy is called as nuclear fusion. Like a fission reaction, the sum of masses before the fusion (i.e. of light nuclei) is more than the sum of masses after the fusion (i.e. of bigger nucleus) and this difference appears as the fusion energy. The most typical fusion reaction is the fusion of two deuterium nuclei into helium.
1H1 + 1H2 —> 2He4 + 21.6 MeV
For the fusion reaction to occur, the light nuclei are brought closer to each other (with a distance of 10–14 m). This is possible only at very high temperature to counter the repulsive force between nuclei. Due to this reason, the fusion reaction is very difficult to perform. The inner core of sun is at very high temperature, and is suitable for fusion, in fact the source of sun's and other star's energy is the nuclear fusion reaction
NUCLEAR REACTOR
An assembly in which a nuclear fission chain reaction is maintained and controlled for the production of nuclear energy, radioactive isotopes, or artificial elements. The nuclear fuel used in a reactor consists of fissile material (e.g. uranium-235 which undergoes fission as a consequence of which two nuclides of approximately equal mass are produced together with between two or three neutrons and a considerable quantity of energy. These neutrons cause further fissions so that a chain reaction develops. In order that the reaction should not get out of control, its progress is regulated by neutron absorbers in control rods, only sufficient free neutrons being allowed to exits in the reactor to maintain the reaction at a constant level. The fissile material is usually mixed with a moderator which slows down, or thermalizes, the fast neutrons emitted during fission, so that they are more likely to cause further fissions of the fissile material than they are to be captured by the uranium-238 isotope.
In a heterogeneous reactor the fuel and the moderator are separated in a geometric pattern called a lattice. In a homogeneous reactor the fuel and the moderator are mixed so that they present a uniform medium to the neutrons (e.g., the fuel, in the form of a uranium salt, may be dissolved in the moderator).
Besides this classification, reactors may be described in a number of ways. They may be described in terms of neutron energy (see fast reactor and thermal reactor) or in terms of function, e.g., a power reactor for generating useful electric power, a production reactor for manufacturing fissile material (see also breeder reactor and converter reactor) and a propulsion reactor for supplying motive power to ships, submarines, or spacecraft. Reactors are also described in terms of their fuel (e.g., plutonium reactor), their moderator (e.g. graphite-moderated reactor), or their coolant (e.g., boiling-water reactor).
CHAIN REACTION
CHAIN REACTION
When a uranium nucleus undergoes fission, three neutrons are produced. These neutrons collide with other uranium nuclei producing nine secondary neutrons. Thus the process gets multiplied quickly. This is called the chain reaction. If it is not controlled the chain reaction continues till the entire fissionable material is disintegrated in a short time emitting a large quantity of heat energy. This causes a violent explosion resulting in the release of tremendous energy in the form of heat and light. This is the basic principle of an atom bomb.
When a uranium nucleus undergoes fission, three neutrons are produced. These neutrons collide with other uranium nuclei producing nine secondary neutrons. Thus the process gets multiplied quickly. This is called the chain reaction. If it is not controlled the chain reaction continues till the entire fissionable material is disintegrated in a short time emitting a large quantity of heat energy. This causes a violent explosion resulting in the release of tremendous energy in the form of heat and light. This is the basic principle of an atom bomb.
NUCLEAR FISSION
NUCLEAR FISSION
The breaking of a heavy nucleus into two or more fragments of comparable masses, with the release of tremendous energy is called as nuclear fission. The most typical fission reaction occurs when slow moving neutrons strike 92U235. The following nuclear reaction takes place.
If more than one of the neutrons produced in the above fission reaction are capable of inducing a fission reaction (provided U235 is available), then the number of fissions taking place at successive stages goes increasing at a very brisk rate and this generates a series of fissions. This is known as chain reaction. The chain reaction takes place only if the size of the fissionable material (U235) is greater than a certain size called the critical size.
92U235 + 0n1 ——> 56Ba141 + 36Kr92 + 3 0n1 + 200 MeV
If the number of fission in a given interval of time goes on increasing continuously, then a condition of explosion is created. In such cases, the chain reaction is known as uncontrolled chain reaction. This forms the basis of atomic bomb.
In a chain reaction, the fast moving neutrons are absorbed by certain substances known as moderators (like heavy water), then the number of fissions can be controlled and the chain reaction is such cases is known as controlled chain reaction. This forms the basis of a nuclear reactor
If more than one of the neutrons produced in the above fission reaction are capable of inducing a fission reaction (provided U235 is available), then the number of fissions taking place at successive stages goes increasing at a very brisk rate and this generates a series of fissions. This is known as chain reaction. The chain reaction takes place only if the size of the fissionable material (U235) is greater than a certain size called the critical size.
92U235 + 0n1 ——> 56Ba141 + 36Kr92 + 3 0n1 + 200 MeV
If the number of fission in a given interval of time goes on increasing continuously, then a condition of explosion is created. In such cases, the chain reaction is known as uncontrolled chain reaction. This forms the basis of atomic bomb.
In a chain reaction, the fast moving neutrons are absorbed by certain substances known as moderators (like heavy water), then the number of fissions can be controlled and the chain reaction is such cases is known as controlled chain reaction. This forms the basis of a nuclear reactor
Tuesday, January 11, 2011
1.WRITE THE USES OF RADIOACTIVE DECAY.
2.WHAT IS THE SI UNIT AND OLD UNIT OF RADIOACTIVITY.
3.BETA PARTICLES COME FROM THE NUCLEUS AND THEY ARE ELECTRONS, BUT THERE NO ELECTRONS INSIDE THE NUCLEUS. EXPLAIN THIS PARADOX.
2.WHAT IS THE SI UNIT AND OLD UNIT OF RADIOACTIVITY.
3.BETA PARTICLES COME FROM THE NUCLEUS AND THEY ARE ELECTRONS, BUT THERE NO ELECTRONS INSIDE THE NUCLEUS. EXPLAIN THIS PARADOX.
APPLICATION OF RADIOACTIVE DECAY
Applications of radioactivity
In medicineRadioisotopes have found extensive use in diagnosis and therapy, and this has given rise to a rapidly growing field called nuclear medicine. These radioactive isotopes have proven particularly effective as tracers in certain diagnostic procedures. As radioisotopes are identical chemically with stable isotopes of the same element, they can take the place of the latter in physiological processes. Moreover, because of their radioactivity, they can be readily traced even in minute quantities with such detection devices as gamma-ray spectrometers and proportional counters. Though many radioisotopes are used as tracers, iodine-131, phosphorus-32, and technetium-99m are among the most important. Physicians employ iodine-131 to determine cardiac output, plasma volume, and fat metabolism and particularly to measure the activity of the thyroid gland where this isotope accumulates. Phosphorus-32 is useful in the identification of malignant tumours because cancerous cells tend to accumulate phosphates more than normal cells do. Technetium-99m, used with radiographic scanning devices, is valuable for studying the anatomic structure of organs.
Such radioisotopes as cobalt-60 and cesium-137 are widely used to treat cancer. They can be administered selectively to malignant tumours and so minimize damage to adjacent healthy tissue.
In industryForemost among industrial applications is power generation based on the release of the fission energy of uranium (see nuclear fission; nuclear reactor: Nuclear fission reactors). Other applications include the use of radioisotopes to measure (and control) the thickness or density of metal and plastic sheets, to stimulate the cross-linking of polymers, to induce mutations in plants in order to develop hardier species, and to preserve certain kinds of foods by killing microorganisms that cause spoilage. In tracer applications radioactive isotopes are employed, for example, to measure the effectiveness of motor oils on the wearability of alloys for piston rings and cylinder walls in automobile engines. For additional information about industrial uses, see radiation: Applications in science and industry.
In scienceResearch in the Earth sciences has benefited greatly from the use of radiometric-dating techniques, which are based on the principle that a particular radioisotope (radioactive parent) in geologic material decays at a constant known rate to daughter isotopes. Using such techniques, investigators have been able to determine the ages of various rocks and rock formations and thereby quantify the geologic time scale (see geochronology: Absolute dating). A special application of this type of radioactivity age method, carbon-14 dating, has proved especially useful to physical anthropologists and archaeologists. It has helped them to better determine the chronological sequence of past events by enabling them to date more accurately fossils and artifacts from 500 to 50,000 years old.
Radioisotopic tracers are employed in environmental studies, as, for instance, those of water pollution in rivers and lakes and of air pollution by smokestack effluents. They also have been used to measure deep-water currents in oceans and snow-water content in watersheds. Researchers in the biological sciences, too, have made use of radioactive tracers to study complex processes. For example, thousands of plant metabolic studies have been conducted on amino acids and compounds of sulfur, phosphorus, and nitrogen.
In medicineRadioisotopes have found extensive use in diagnosis and therapy, and this has given rise to a rapidly growing field called nuclear medicine. These radioactive isotopes have proven particularly effective as tracers in certain diagnostic procedures. As radioisotopes are identical chemically with stable isotopes of the same element, they can take the place of the latter in physiological processes. Moreover, because of their radioactivity, they can be readily traced even in minute quantities with such detection devices as gamma-ray spectrometers and proportional counters. Though many radioisotopes are used as tracers, iodine-131, phosphorus-32, and technetium-99m are among the most important. Physicians employ iodine-131 to determine cardiac output, plasma volume, and fat metabolism and particularly to measure the activity of the thyroid gland where this isotope accumulates. Phosphorus-32 is useful in the identification of malignant tumours because cancerous cells tend to accumulate phosphates more than normal cells do. Technetium-99m, used with radiographic scanning devices, is valuable for studying the anatomic structure of organs.
Such radioisotopes as cobalt-60 and cesium-137 are widely used to treat cancer. They can be administered selectively to malignant tumours and so minimize damage to adjacent healthy tissue.
In industryForemost among industrial applications is power generation based on the release of the fission energy of uranium (see nuclear fission; nuclear reactor: Nuclear fission reactors). Other applications include the use of radioisotopes to measure (and control) the thickness or density of metal and plastic sheets, to stimulate the cross-linking of polymers, to induce mutations in plants in order to develop hardier species, and to preserve certain kinds of foods by killing microorganisms that cause spoilage. In tracer applications radioactive isotopes are employed, for example, to measure the effectiveness of motor oils on the wearability of alloys for piston rings and cylinder walls in automobile engines. For additional information about industrial uses, see radiation: Applications in science and industry.
In scienceResearch in the Earth sciences has benefited greatly from the use of radiometric-dating techniques, which are based on the principle that a particular radioisotope (radioactive parent) in geologic material decays at a constant known rate to daughter isotopes. Using such techniques, investigators have been able to determine the ages of various rocks and rock formations and thereby quantify the geologic time scale (see geochronology: Absolute dating). A special application of this type of radioactivity age method, carbon-14 dating, has proved especially useful to physical anthropologists and archaeologists. It has helped them to better determine the chronological sequence of past events by enabling them to date more accurately fossils and artifacts from 500 to 50,000 years old.
Radioisotopic tracers are employed in environmental studies, as, for instance, those of water pollution in rivers and lakes and of air pollution by smokestack effluents. They also have been used to measure deep-water currents in oceans and snow-water content in watersheds. Researchers in the biological sciences, too, have made use of radioactive tracers to study complex processes. For example, thousands of plant metabolic studies have been conducted on amino acids and compounds of sulfur, phosphorus, and nitrogen.
RADIOACTIVITY
Decay types
Radio nuclides of different types can be involved in several different reactions that produce radiant energy. The three main types of ionizing radiation are alpha, beta, and gamma.
Alpha decay- Two protons and two neutrons emitted from nucleus
Beta decay- A neutron emits an electron and an antineutrino and becomes a proton
Gamma decay- Excited nucleus releases a high-energy photon
ALPHA DECAY
BETA DECAY
GAMA DECAY
Composition Alpha particle Beta particle Electromagnetic radiation
Symbol α β γ
Charge 2 -1 0
Mass 4 1/1837 0
Penetrating power Low Moderate Very high
symbol of radioactivityMonday, January 10, 2011
FOLLOW UP QUESTION
1.IS MASS ENERGY RELATION VALID IN CHEMICAL REACTION PRODUCING ENERGY .EXPLAIN
2.HOW DOES BINDING ENERGY VALUE AFFECT THE STABILITY OF THE NUCLEUS.
3. CALCULATE THE AMOUNT OF ENERGY RELEASED WHEN 1kg DISAPPEARS COMPLETELY.
4.WRITE A BRIEF HISTORY REGARDING THE DISCOVERY OF NEUTRON.
5.WHAT IS BINDING ENERGY.WHAT HAPPENS TO THE STABILITY OF NUCLEUS WHEN BINDING ENERGY INCREASES .
6.WHAT IS THE NATURE OF THE BINDING ENERGY CURVE FOR LOW AND HIGH VALUES OF MASS NUMBER.
7.WHAT IS THE NATURE OF THE BINDING ENERGY CURVE FOR MASS NUMBER WHICH RANGES FROM 40-120.
8.WHAT IS NATURE OF THE FORCE BETWEEN NUCLEONS
a)IF THE DISTANCE BETWEEN THE NUCLEONS LESS THAN 3fm.
b)IF THE DISTANCE OF SEPARATION IS Ro fm AND 3fm.
9.WHICH ARE THE CONSTITUENTS OF NUCLEUS
10.WHAT HAPPENS TO THE SIZE OF THE NUCLEUS WHEN NUMBER OF NUCLEONS IS INCREASED
2.HOW DOES BINDING ENERGY VALUE AFFECT THE STABILITY OF THE NUCLEUS.
3. CALCULATE THE AMOUNT OF ENERGY RELEASED WHEN 1kg DISAPPEARS COMPLETELY.
4.WRITE A BRIEF HISTORY REGARDING THE DISCOVERY OF NEUTRON.
5.WHAT IS BINDING ENERGY.WHAT HAPPENS TO THE STABILITY OF NUCLEUS WHEN BINDING ENERGY INCREASES .
6.WHAT IS THE NATURE OF THE BINDING ENERGY CURVE FOR LOW AND HIGH VALUES OF MASS NUMBER.
7.WHAT IS THE NATURE OF THE BINDING ENERGY CURVE FOR MASS NUMBER WHICH RANGES FROM 40-120.
8.WHAT IS NATURE OF THE FORCE BETWEEN NUCLEONS
a)IF THE DISTANCE BETWEEN THE NUCLEONS LESS THAN 3fm.
b)IF THE DISTANCE OF SEPARATION IS Ro fm AND 3fm.
9.WHICH ARE THE CONSTITUENTS OF NUCLEUS
10.WHAT HAPPENS TO THE SIZE OF THE NUCLEUS WHEN NUMBER OF NUCLEONS IS INCREASED
NUCLEAR BINDING ENERGY
Mass defect
The sum of the masses of the constituent nuclei is always more than the actual mass of the resulting nucleus. The difference between the masses of the constituent nucleons and the actual mass of the nucleus is called the mass defect. Let M be the mass of the nucleus having the mass number A and atomic number Z.
Mass defect,∆m= [Zmp+(A-Z)mn]-M
Where mp is the mass of the proton and mn is the mass of the neutron
Binding energy
When protons and neutrons combine to form a nucleus, the mass that disappear (mass defect) is converted into equivalent amount of energy. This energy is called binding energy of the nucleus.
Binding energy =mass defect x c2=∆mxc2=[Zmp+(A-Z)mn-M]c2
The binding energy determines the stability of the nucleus. If the binding energy is large the nucleus is stable and vice versa. The binding energy must be supplied to the nucleus to split into completely into its constituent nucleons.
MASS-ENERGY RELATION
Einstein’s mass-energy relation, relationship between mass (m) and energy (E) in the special theory of relativity of Albert Einstein, embodied by the formula E = mc2, where c equals 300,000 km (186,000 miles) per second—i.e., the speed of light.
NUCLEUS AND ITS COMPOSITION
NUCLEUS AND ITS COMPOSITION
Nucleus and Nuclear Particles:
Nucleus is small and positively charged part of an atom at the center where entire mass of the atom is concentrated. E. Rutherford and his co-workers conducted a series of scattering experiments, on the basis of which the existence of the nucleus was first proposed in1911. These experiments helped to understand the arrangement of sub atomic particles (electrons, protons and neutrons) in an atom. From the experimental observations it was concluded that the protons and neutrons are present in the nucleus where as electrons are present in the empty space around the nucleus.
ATOMIC NUMBER: It is the numbers of electrons present outside the nucleus or the number of protons present inside the nucleus. It is denoted by (Z).
Atomic Number (Z) = Number of electrons (e) OR Number of Protons (p)
NUCLEONS: The sub atomic particles (protons and neutrons) of nucleus are collectively called nucleons. The total number of nucleons is denoted byA and is called mass number of the nucleus.
Mass Number (A) = Number of Protons (p) + Number of Neutrons (n)
REPRESENTATION OF NUCLIDE: The nucleus of any atom is represented by specifying the atomic number as a subscript at the left hand bottom of the atomic symbol and mass number as a superscript at the left hand top of the symbol. For example, carbon atom, its symbol is C; atomic number is 6, mass number is12. It is represented as12c .Such symbols are called as nuclides.
NUCLEAR DIMENSIONS:
The radius of the nucleus is of the order of 10-12 and that of atom is 10-8
•
The radii of the various nuclei can be calculated by the following relation
r= R0A1/3
Where; r= radius of nucleus
A= mass number
R0 = constant (1.4 x 10-24cm)
•
Nuclear Dimensions are expressed in Fermi units, 1Fermi = 10-13cm.
•
Area of cross section of nucleus is measured in unit called barn
(1barn = 10-24cm2)
•
Radius of nucleus is 105 times smaller than that of atom.
•
Density is of the order of 1014gcm-3.
•
Volume is of the order of 10-38 cm3.
ISOTOPES, ISOBARS, ISOTONES,
Isotopes:
These are the atoms having same atomic number but different mass numbers.
They contain same number of protons but different number of nucleons.
Isobars:
The atoms having different atomic numbers but same mass number are called isobars. They contain same number of nucleons but different number of protons.
Calcium and Argon are isobars of each other having same mass number but different atomic number.
Similarly Lead and Bismuth are isobars of each other.
Isotones:
These are the atoms having same number of neutrons but different number of nucleons. But by appearance they have different number atomic number and different mass number but the number of neutrons is same all these nuclides have different mass number and atomic number. But if we calculate the number of neutron in each case it is coming out to bethe16.
Because Number of neutrons = mass number (A) – atomic number (Z)
Atomic mass
One way scientists measure the size of something is by its mass. Scientists can even measure very, very tiny things like atoms. One measure of the size of an atom is its "atomic mass". Almost all of the mass of an atom (more than 99%) is in its nucleus, so "atomic mass" is pretty much a measure of the size of the nucleus of an atom.
The nucleus of an atom is made up of protons and neutrons. Protons and neutrons are almost exactly the same size. If you add up the number of protons and neutrons in the nucleus of an atom, you get that atom's atomic mass. A simple hydrogen atom has just one proton and zero neutrons. Its atomic mass is 1. The most common kind of carbon atom has 6 neutrons and 6 protons. It has an atomic mass of 12.
All atoms of a certain element have the same number of protons. Oxygen atoms always have 8 protons; carbon atoms all have 6 protons. Most atoms come in different types called isotopes. Isotopes have different numbers of neutrons. The most common isotope of carbon has 6 neutrons and 6 protons. Its atomic mass is 12. A rare, radioactive isotope of carbon has 8 neutrons. Its atomic mass is 14 ( = 6 protons + 8 neutrons).
Mass defect
The sum of the masses of the constituent nuclei is always more than the actual mass of the resulting nucleus. The difference between the masses of the constituent nucleons and the actual mass of the nucleus is called the mass defect. Let M be the mass of the nucleus having the mass number A and atomic number Z.
Mass defect,∆m= [Zmp+(A-Z)mn]-M
Where mp is the mass of the proton and mn is the mass of the neutron
Binding energy
When protons and neutrons combine to form a nucleus, the mass that disappear (mass defect) is converted into equivalent amount of energy. This energy is called binding energy of the nucleus.
Binding energy =mass defect x c2=∆mxc2=[Zmp+(A-Z)mn-M]c2
The binding energy determines the stability of the nucleus. If the binding energy is large the nucleus is stable and vice versa. The binding energy must be supplied to the nucleus to split into completely into its constituent nucleons.
MASS-ENERGY RELATION
Einstein’s mass-energy relation, relationship between mass (m) and energy (E) in the special theory of relativity of Albert Einstein, embodied by the formula E = mc2, where c equals 300,000 km (186,000 miles) per second—i.e., the speed of light.
NUCLEUS AND ITS COMPOSITION
NUCLEUS AND ITS COMPOSITION
Nucleus and Nuclear Particles:
Nucleus is small and positively charged part of an atom at the center where entire mass of the atom is concentrated. E. Rutherford and his co-workers conducted a series of scattering experiments, on the basis of which the existence of the nucleus was first proposed in1911. These experiments helped to understand the arrangement of sub atomic particles (electrons, protons and neutrons) in an atom. From the experimental observations it was concluded that the protons and neutrons are present in the nucleus where as electrons are present in the empty space around the nucleus.
ATOMIC NUMBER: It is the numbers of electrons present outside the nucleus or the number of protons present inside the nucleus. It is denoted by (Z).
Atomic Number (Z) = Number of electrons (e) OR Number of Protons (p)
NUCLEONS: The sub atomic particles (protons and neutrons) of nucleus are collectively called nucleons. The total number of nucleons is denoted byA and is called mass number of the nucleus.
Mass Number (A) = Number of Protons (p) + Number of Neutrons (n)
REPRESENTATION OF NUCLIDE: The nucleus of any atom is represented by specifying the atomic number as a subscript at the left hand bottom of the atomic symbol and mass number as a superscript at the left hand top of the symbol. For example, carbon atom, its symbol is C; atomic number is 6, mass number is12. It is represented as12c .Such symbols are called as nuclides.
NUCLEAR DIMENSIONS:
The radius of the nucleus is of the order of 10-12 and that of atom is 10-8
•
The radii of the various nuclei can be calculated by the following relation
r= R0A1/3
Where; r= radius of nucleus
A= mass number
R0 = constant (1.4 x 10-24cm)
•
Nuclear Dimensions are expressed in Fermi units, 1Fermi = 10-13cm.
•
Area of cross section of nucleus is measured in unit called barn
(1barn = 10-24cm2)
•
Radius of nucleus is 105 times smaller than that of atom.
•
Density is of the order of 1014gcm-3.
•
Volume is of the order of 10-38 cm3.
ISOTOPES, ISOBARS, ISOTONES,
Isotopes:
These are the atoms having same atomic number but different mass numbers.
They contain same number of protons but different number of nucleons.
Isobars:
The atoms having different atomic numbers but same mass number are called isobars. They contain same number of nucleons but different number of protons.
Calcium and Argon are isobars of each other having same mass number but different atomic number.
Similarly Lead and Bismuth are isobars of each other.
Isotones:
These are the atoms having same number of neutrons but different number of nucleons. But by appearance they have different number atomic number and different mass number but the number of neutrons is same all these nuclides have different mass number and atomic number. But if we calculate the number of neutron in each case it is coming out to bethe16.
Because Number of neutrons = mass number (A) – atomic number (Z)
Atomic mass
One way scientists measure the size of something is by its mass. Scientists can even measure very, very tiny things like atoms. One measure of the size of an atom is its "atomic mass". Almost all of the mass of an atom (more than 99%) is in its nucleus, so "atomic mass" is pretty much a measure of the size of the nucleus of an atom.
The nucleus of an atom is made up of protons and neutrons. Protons and neutrons are almost exactly the same size. If you add up the number of protons and neutrons in the nucleus of an atom, you get that atom's atomic mass. A simple hydrogen atom has just one proton and zero neutrons. Its atomic mass is 1. The most common kind of carbon atom has 6 neutrons and 6 protons. It has an atomic mass of 12.
All atoms of a certain element have the same number of protons. Oxygen atoms always have 8 protons; carbon atoms all have 6 protons. Most atoms come in different types called isotopes. Isotopes have different numbers of neutrons. The most common isotope of carbon has 6 neutrons and 6 protons. Its atomic mass is 12. A rare, radioactive isotope of carbon has 8 neutrons. Its atomic mass is 14 ( = 6 protons + 8 neutrons).
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