Radioactivity
i. Alpha particles
ii. Beta particle, and
iii. Gamma rays.
In an alpha decay, the nucleus emits an alpha particle. An alpha particle is a helium nucleus, made up of two protons and two neutrons.
In beta decay, the nucleus emits a beta particle. A beta particle is a fast moving electron.
In gamma decay, the nucleus emits gamma rays. Gamma rays are electromagnetic radiation of very high frequency.
Radioactivity detectors that work because of the ionizing ability of the radiations are :
(a) Geiger- Muller tube (G-M tube)
(b) Electroscope
(c) Spark counter
(d) Cloud chamber
They can be used to differentiate between alpha, beta and gamma radiations.
The nature of radioactivity was discovered by husband and wife scientists, Marie Curie (1867-1934) and Pierre Curie (1859- 1906).
Geiger Miller Tube
Cloud chamber
The track patterns formed in the cloud chamber can be used to differentiate between alpha, beta and gamma radiations.
Alpha radiation produces thick, straight tracks. The tracks are thick because of their high ionizing ability. Straight tracks are due to their large mass, making alpha particle difficult to deflect (high inertial).
Beta radiation produces thin; twisted tracks. The thin twisted tracks are due to the weak ionizing ability of the beta particle. Twisted tracks are due to their small mass, making beta particles easier to deflect.
Gamma radiation produces short, thin and scattered tracks. This is due to the extremely weak ionizing ability of gamma rays.
Spark counter
When a radioactive source which produces alpha particles is brought near, the air between the gauze and the wire is ionized by it.
Radioactive Emissions
Properties of radioactive emissions:
A) Structure and Charge
1. Alpha particle
an alpha particle is the nucleus of helium atom and made up of two protons and two neutrons. it is positively charged (+2).
2. Beta particle
A beta particle is a fast moving electron and has a negative charge (-1).
3. Gamma ray
Gamma ray is an electromagnetic wave; it moves at the speed of light, c ( 3x10^8 m/s). Gamma ray does not carry any charge.
Alpha and beta particles have opposite charges, thus they are deflected in opposite directions.
Gamma ray is neutral , thus it is not deflected by the magnetic field.
B) Ionising Power and Penetrating Power
Alpha particle have a relatively high ionising power and hence a relatively low penetrating power. on the other hand, gamma ray which has a relatively low ioning power has a realatively high penetrating power.
alpha particles can be stopped by a piece of paper, beta particles are stopped by a few centimetres aluminum sheets, while gamma ray can only be stopped by a few centimetres of lead.
Particles that ionise other atoms strongly have a low penetrating power because they lose energy each time they ioning an atom.
Spontaneous radioactive emissions are not affected by external conditions like temperature and pressure.
Summary
Radioactive Decay
Radioactive decay is a spontaneous process in which an unstable nucleus changes into amore stable nucleus by emitting radiation.
An unstable nucleus emits radiation in the form of alpha particles, beta particles or gamma rays.
Alpha decay is a spontaneous process of emitting an alpha particle from an unstable nucleus.
Beta decay is a spontaneous process of emitting a bata particle from an unstable nucleus.
Gamma decay is a spontaneous process of emitting gamma ray from an unstable nucleus.
The unstable nucleus before a radioactive decay is known as the parent nuclide. During radiactive decay, the parent nuclide is transformed into a more stable nucleus known as thedaughter nuclide.
A) Structure and Charge
1. Alpha particle
an alpha particle is the nucleus of helium atom and made up of two protons and two neutrons. it is positively charged (+2).
2. Beta particle
A beta particle is a fast moving electron and has a negative charge (-1).
3. Gamma ray
Gamma ray is an electromagnetic wave; it moves at the speed of light, c ( 3x10^8 m/s). Gamma ray does not carry any charge.
Alpha and beta particles have opposite charges, thus they are deflected in opposite directions.Gamma ray is neutral , thus it is not deflected by the magnetic field.
B) Ionising Power and Penetrating Power
Alpha particle have a relatively high ionising power and hence a relatively low penetrating power. on the other hand, gamma ray which has a relatively low ioning power has a realatively high penetrating power.
alpha particles can be stopped by a piece of paper, beta particles are stopped by a few centimetres aluminum sheets, while gamma ray can only be stopped by a few centimetres of lead.
Particles that ionise other atoms strongly have a low penetrating power because they lose energy each time they ioning an atom.
Spontaneous radioactive emissions are not affected by external conditions like temperature and pressure.
Summary
Radioactive Decay
Radioactive decay is a spontaneous process in which an unstable nucleus changes into amore stable nucleus by emitting radiation.
An unstable nucleus emits radiation in the form of alpha particles, beta particles or gamma rays.
Alpha decay is a spontaneous process of emitting an alpha particle from an unstable nucleus.
Beta decay is a spontaneous process of emitting a bata particle from an unstable nucleus.
Gamma decay is a spontaneous process of emitting gamma ray from an unstable nucleus.
The unstable nucleus before a radioactive decay is known as the parent nuclide. During radiactive decay, the parent nuclide is transformed into a more stable nucleus known as thedaughter nuclide.
Half-life
The time taken for an unstable radioactive nuclide to decay to half its original number is called the half-life.
The symbol for half-life is T1/2
2.Determine half-life from a decay curve
The decay graph is a graph of the number of atom/ reactivity/ mass against time.The number of number of atom/ reactivity/ mass of radioactive sample decreases exponentially with time.
The half-life of the same radioactive element or nuclide is the same.
Different nuclides have different decay rates, thus different nuclides have different half-life.
Nuclear Fission
1. What is atomic mass unit (a.m.u)?
The symbol for the atomic mass unit is u.
1 u is defined as 1/12 x ( mass of the carbon-12 atom)
1 u = 1,66 x 10 ^-27 kg.
2. Describe nuclear fission.
A nuclear fission is a nuclear reaction in which a heavy nucleus splits into split into two or more lighter nuclei which the release of energy.
The nucleon number and proton number must be balanced in the nuclear equation.
3. Describe chain reactions.
A chain reaction is a process in which at least one neutron produced in a fission induces a second fission.
A neutron produced in the second fission induces a third fission, and the process is
The symbol for the atomic mass unit is u.
1 u is defined as 1/12 x ( mass of the carbon-12 atom)
1 u = 1,66 x 10 ^-27 kg.
2. Describe nuclear fission.
A nuclear fission is a nuclear reaction in which a heavy nucleus splits into split into two or more lighter nuclei which the release of energy.
The nucleon number and proton number must be balanced in the nuclear equation.
3. Describe chain reactions.
A chain reaction is a process in which at least one neutron produced in a fission induces a second fission.
A neutron produced in the second fission induces a third fission, and the process is
Nuclear Fusion
Nuclear fusion is the reaction nuclei of two light nuclides are fused together to form a single heavies nucleus with the release of energy.
Learn more here:
http://www.visionlearning.com/library/flash_viewer.php?oid=2747
Advantages of using nuclear fusion as a power source are;
i) Hydrogen isotopes used as fuel are cheap and easily available.
ii) Products of nuclear fusion are not radioactive and do not cause pollution.
http://www.astro.ubc.ca/~scharein/a311/Sim/fusion/Fusion.html
Two suitable conditions in the sun that allows nuclear fusion to take place are:
i) high temperature, and
ii) high particle density.
Learn more here:
http://www.visionlearning.com/library/flash_viewer.php?oid=2747
Advantages of using nuclear fusion as a power source are;
i) Hydrogen isotopes used as fuel are cheap and easily available.
ii) Products of nuclear fusion are not radioactive and do not cause pollution.
http://www.astro.ubc.ca/~scharein/a311/Sim/fusion/Fusion.html
Two suitable conditions in the sun that allows nuclear fusion to take place are:
i) high temperature, and
ii) high particle density.
