RADIOACTIVITY*

STRUCTURE OF ATOM*

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MASS NUMBER*

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ISOTOPES*

ZSAMEADIFFERENT*

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RADIOACTIVE DECAY*

*Spontaneous decaying process of an unstable nucleus by emitting energetic particles to become a more stable nucleus. RADIOACTIVITY

*The decaying process is spontaneous happens by itselfNot affected by factors such as temperature, pressure, electric field, magnetic field and combination with other elements to form compound

*Substances which contain unstable isotopes are called radioactive substances.

Radioactive radiations which are emitted consists of alpha particles beta particlesgamma rays

*CHARACTERISTICS OF RADIOACTIVE RADIATIONS

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*Devices used to detect radioactive radiation Spark counterGeiger-Muller tube Photographic plateCloud chamber

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ALPHA DECAYThe emission of radioactive radiations causes the change in the proton number and number of neutrons in the nucleus.Alpha particle have 4 nucleon number and 2 proton number

After emitted, the nucleus loses 2 protons and 2 neutrons.So, the nucleon number of the new element decrease by 4 and the proton number decrease by 2

ALPHA DECAY*

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*BETADECAYBETADECAYA beta decay causes the proton number of the new element formed to be increased by 1.

The nucleon number remains unchanged

BETADECAY*

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*GAMMARAYA gamma ray is an electromagnetic wave.

It has no mass and not charged.

After emit, the proton number and nucleon number of the original element remain unchanged

GAMMARAY*

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*RADIOACTIVE DECAY SERIES

When an unstable radioactive nucleus decays, the daughter nucleus produced may not be stable.

The daughter nucleus will continue to undergo a series of decay until the nucleus is stable.

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EXTRA EXERCISES1THE NUCLIDE THORIUM-232 (PROTON NUMBER 90) DECAY BY EMITTING AN ALPHA PARTICLE. WRITE DOWN THE EQUATIONFOR THE DECAY PROCESS AND THE NAME OF DAUGHTERNUCLIDE.*

HALF LIFE*The half-life of a radioactive nuclide is the time taken for the number of undecayed nuclei to be reduced to half of its original number.

*After the half-life, the activity and number of atoms which have not decayed become half.

Different radioactive nuclides have different half-lives.

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Use OF RADIOISOTOPES*

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*NUCLEAR ENERGYATOMIC MASS UNIT (a.m.u)

used to state the mass of an atom, a proton and a neutron.One atom of carbon-12 is define as having a mass of 12 u1 atomic mass unit is 1/12 of the mass of one atom of carbon-12.The mass 1 atom of carbon-12 is 1.99265 x 10-26 kg

So, 1 u =?

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*Radium-226 undergoes alpha decay to become Radon-222. The equation for the decay is: Calculate the energy released in Joule. [ = 226.025406 u,

= 222.017574 u, = 4.002603 u

1 u = 1.66 x 10-27 kg c = 3.00 x 10^8 ms-1]

*The equation below shows the decay of radium-226. the mass defect is 0.0052289 u.

Calculate the energy which is released. [1 u = 1.66 x 10-27 kg , c = 3.00 x 10 ^8 ms-1 ]

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