Nuclear Chemistry Chapter 21
Radioisotopes Nuclei of unstable isotopes are called radioisotopes. An unstable nucleus releases energy and/or mass by emitting radiation during the process of radioactive decay
Radiation Three Types Alpha Helium Nucleus Beta Electron Gamma Light wave
Symbols Alpha Beta Gamma
Radiation
Radiation
Nuclear Symbols Table O
Nuclear Stability For smaller atoms, a ratio of 1:1 neutrons to protons helps to maintain stability C-12, N-14, O-16 For larger atoms, more neutrons than protons are required to maintain stability Pb-207, Au-198, Ta-181
Nuclear Stability
Radioactive Decay Radioisotopes will undergo decay reactions to become more stable Alpha Decay Beta Decay Positron Emission Electron Capture
Alpha Decay
Beta Decay
Positron Emission
Electron Capture 37 81 𝑅𝑏 + −1 0 𝑒 → 36 81 𝐾𝑟
Transmutations Any reaction where one element is transformed into a different element Two main types Natural Artificial
Example X
Example X
Example X
Fission Splitting of a larger atom into two or more smaller pieces Nuclear Power Plants One Example:
Fission
Fusion Joining of two or more smaller pieces to make a larger piece Sun, Stars One Example:
Fusion
Energy Production Energy is produced by a small amount of mass being converted to energy More energy is produced by fusion than any other source E=mc2
Mass Difference The mass of a nucleus weighs less than the mass of the individual protons and neutrons He Nucleus 4.00150u 2 protons 2(1.00728) 2.01456 2 neutrons 2(1.00866) 2.01732 4.03188u
Mass Defect Mass difference between nucleus and individual particles Nucleons 4.03188 u Nucleus - 4.00150 u Mass Defect 0.03038 u
Nuclear Binding Energy In order to break apart the individual particles in a nucleus, energy must be added. The added energy is converted back to mass When particles form a nucleus, energy is released
Nuclear Binding Energy per Nucleon
Half Life Amount of time for half the atoms in a radioactive sample to decay into a new element Measure of time, t1/2
Half Life Equation 𝑙𝑛 𝑁𝑡 𝑁𝑜 =−𝑘𝑡 𝑙𝑛 𝑁𝑜 𝑁𝑡 =𝑘𝑡
Half Life Equation 𝑙𝑛 𝑁𝑜 𝑁𝑡 =𝑘𝑡 𝑙𝑛 2 1 =𝑘 𝑡 1/2 𝑘= 0.693 𝑡 1/2
Example