Nuclear Chemistry “Bravo” Test 1954 – 15,000 kilotons

Radioactivity and Nuclear Energy Objective: To learn the types of radioactive decay Objective: To learn to write nuclear equations that describes radioactive decay Objective: To learn how one element may be changed into another by particle bombardment

What makes an atom radioactive? Radioactivity: the spontaneous decomposition of a nucleus to form another nucleus and produce one or more particles. -the neutrons act as glue holding the nucleus together -the heavier the atom, the more likely it is to be radioactive -if the number of protons in the nucleus exceeds 83, then the nuclide is radioactive

Types of Radioactive Decay  alpha production (  He): helium nucleus  beta production (  e):  gamma ray production (  ):  alpha production (  He): helium nucleus  beta production (  e):  gamma ray production (  ):

Specifying Isotopes 5 X A Z X = the symbol of the element A = mass number (protons + neutrons) Z = the atomic number (number of protons)

Nuclear Symbols Element symbol Mass number, A (p + + n o ) Atomic number, Z (number of p + )

Key to Understanding Nuclear Reactions In nuclear reactions, both the atomic number Z and the mass number A must be conserved

Balancing Nuclear Equations 226 = 4 + ____ = 2 + ___ 86 Atomic number 86 is radon, Rn Rn

Alpha Decay Alpha production (  ): an alpha particle is a helium nucleus Alpha decay is limited to heavy, radioactive nuclei

Alpha (α) Decay E1E1 P+N P P-2 + He 4 2 E2E2 P+N -4 an alpha particle (helium nucleus) is produced

Alpha Radiation Limited to VERY large nucleii.

Example of Alpha Decay Ra He 4 2 Rn Radium 222 decays by α particle production to Radon

Beta Decay Beta production (  ): A beta particle is an electron ejected from the nucleus Beta emission converts a neutron to a proton

Beta (β) Decay Beta emission converts a neutron to a proton E1E1 P+N P P+1 + e 0 E2E2 P+N

Beta Radiation Converts a neutron into a proton.

Example of Beta Decay Notice the mass of the beta particle is zero; it is so small that is must be neglected. C e 0 N 14

Example of Beta Decay Th e 0 Pa 234 Thorium 234 decays by β particle production to Protactinium 234 (notice: no change in mass number A, and an increase of 1 in atomic number Z)

Gamma Ray Production Gamma ray production (  ): Gamma rays are high energy photons produced in association with other forms of decay. Gamma rays are massless and do not, by themselves, change the nucleus

Gamma Ray Production Gamma ray production (  ): Gamma rays are high energy photons produced in association with other forms of decay. Gamma rays are massless and do not, by themselves, change the nucleus

Positron Production Positron emission: Positrons are the anti- particle of the electron Positron emission converts a proton to a neutron

Positron Production E1E1 P+N P P-1 + e 0 1 E2E2 P+N Positron emission converts a proton to a neutron

Electron Capture Electron capture: (inner-orbital electron is captured by the nucleus) Electron capture converts a proton to a neutron

Types of Radiation

Nuclear Stability Decay will occur in such a way as to return a nucleus to the band (line) of stability. The most stable nuclide is Iron-56 If Z > 83, the nuclide is radioactive

A Decay Series A radioactive nucleus reaches a stable state by a series of steps Graphic – Wikimedia Commons User Tosaka