Nuclear Chemistry “Bravo” Test 1954 – 15,000 kilotons
Chapter 19: Radioactivity and Nuclear Energy Objective 12: To learn the types of radioactive decay (Section 19.1) Objective 13: To learn to write nuclear equations that describes radioactive decay (Section 19.1) Objective 14: To learn how one element may be changed into another by particle bombardment (Section 19.2)
What makes an atom radioactive? Radioactivity: the spontaneous decomposition of a nucleus to form another nucleus and produce one or more particles. -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 -all of the positive charge is concentrated in one area; therefore the nucleus is unstable
Types of Radioactive Decay • alpha production (a, He): helium nucleus • beta production (b, e): • gamma ray production (g):
Specifying Isotopes A X = the symbol of the element A = mass number (protons + neutrons) Z = the atomic number (number of protons) X Z
Nuclear Symbols Mass number, A (p+ + no) Element symbol Atomic number, Z (number of p+)
Key to Balancing Nuclear Equations In nuclear reactions, both the atomic number Z and the mass number A must be conserved
Balancing Nuclear Equations 222 226 = 4 + ____ 222 Rn 86 86 88 = 2 + ___ Atomic number 86 is radon, Rn
Alpha Decay Alpha production (a): an alpha particle is a helium nucleus Alpha decay is limited to heavy, radioactive nuclei
Alpha (α) Decay an alpha particle (helium nucleus) is produced P+N -4 4 P+N He + E2 E1 P 2 P-2
Alpha Radiation Limited to VERY large nucleii.
Example of Alpha Decay Radium 222 decays by α particle production to Radon 218 4 222 218 He + Rn Ra 88 2 86
Beta Decay Beta production (b): A beta particle is an electron ejected from the nucleus Beta emission converts a neutron to a proton
Beta (β) Decay P+N P+N 0 e + E2 E1 P -1 P+1 Beta emission converts a neutron to a proton
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. 14 0 14 e N + C 6 -1 7
Example of Beta Decay 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) 234 234 0 e Pa + Th 90 -1 91
Gamma Ray Production Gamma ray production (g): 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 (g): 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 P+N P+N 0 e + E2 E1 P 1 P-1 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
NuclearStability 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
A Decay Series A radioactive nucleus reaches a stable state by a series of steps Graphic – Wikimedia Commons User Tosaka
Particle Bombardment Nuclear transformation involves changing one element into another by bombarding it with small nuclei, protons, or neutrons in a particle accelerator
