Radioactive Decay

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List the different types of symbols used in nuclear reactions and their symbols.

Radioactive Decay

Essential Question: How do the different types of radioactive decay affect the nucleus of the atom?

History of Radioactive DecayHenri Becquerel discovered that sunlight was not needed to produce electromagnetic rays

Marie Curie and Pierre Curie found that Uranium and Thorium were the only radioactive element in 1896

1898, The Curies discovered two new radioactive elements; polonium and radium.

Radioactive Decay

Radioactive decay is the spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles, electromagnetic radiation or both.

Radioactive Decay

Nuclear Radiation are the particles or electromagnetic radiation that are emitted from the nucleus during radioactive decay.

Radioactive Decay

A radioactive nuclide is one that is unstable and undergoes radioactive decay.

All nuclides beyond atomic number 83 are unstable and radioactive.

Types of Radioactive Decay

Some common types of radioactive decay are listed in the chart below:

Type Symbol Charge Mass(amu)Alpha

particle2+ 4.0015062

Beta particle 1- .0005486Positron 1+ .0005486

Gamma ray ϒ 0 0

Alpha Emission

• Alpha particle (α) is two protons and two neutrons bound together.

• Emitted from the nucleus during radioactive decay

• Mainly only emitted from heavy nuclei

• During alpha emission the number of protons and the number of neutrons are reduced in order to increase the stability of the nucleus

Beta Emission• A Beta particle is an electron emitted from the nucleus during

radioactive decay.• Unstable nuclides with a large neutron/proton ratio (above the

band of stability)• Atom needs to decrease the number of neutrons to become

stable• A neutron is converted to a proton and an electron and is

released form the nucleus

Positron Emission• A positron is a particle that has the same mass as an

electron, but has a positive e charge.

• Emitted from the nucleus during radioactive decay

• Unstable nuclides with small neutron/proton ratios (below the band of stability)

• Atoms need to decrease the number of protons in order to become stable

• A proton can be converted into a neutron by emitting a positron.

Electron Capture

• In electron capture, and electron is captured form the inner orbitals of the atom

• This happens when the neutron/proton ratio is too small

• The electron combines with a proton to produce a neutron

Gamma Emission

• Gamma emissions are high energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground(lowest possible) energy state

• Usually occurs immediately following other types of decays.

• The nucleus is left in an excited state, energy has to be released for the nucleus to return to a ground state.

Half Life

• Half life (t1/2) is the time required for half the atoms of a radioactive nuclide to decay

• Each radioactive nuclide has its own half life

• More stable nuclides decay slowly and have a longer half life

• Less stable nuclides decay very quickly, and have shorter half lives