> Nuclear Chemistry : Radioactive Decay Quiz
Nuclear Chemistry : Radioactive Decay Quiz
Unstable atoms gain stability by emitting radiation. The stability of an atom’s nucleus can be correlated with its neutron-to-proton (n/p) ratio. Stable nuclei of atoms with low atomic numbers (X< 20) have a n/p ratio of 1:1. For larger nuclei, the n/p ratio is closer to 1.5:1. Stable nuclei are found in an area called the Band of Stability. The Band of Stability begins with hydrogen (atomic #1) and ends with bismuth-209. Every element greater than atomic #83 is radioactive.
The type of decay an isotope undergoes depends on the cause of its instability. Atoms above the Band of Stability have too many neutrons, and atoms below the Band of Stability have too many protons. As a result, they undergo specific kinds of decay. They do this in order to become stable nuclei.
Isotopic notation: 14 (mass number) 7 (atomic number) N (element symbol)
14 7 N
Atoms above the Band of Stability undergo beta decay, which is the emission of a beta particle. Beta particles carry an electric charge of -1. This type of decay reduces the number of neutrons in the nucleus and brings the atom closer to the Band of Stability.
Example of a nucleus undergoing beta decay:
14 6 C --> 14 7 N + 0 -1 e
“0 -1 e” represents the beta particle
**The mass number NEVER changes in beta decay and the atomic number changes by 1.
Atoms below the Band of Stability undergo alpha decay, which is the emission of an alpha particle (or a helium nucleus). Alpha particles carry an electric charge of +2. This kind of decay reduces the number of protons in the nucleus.
Example of a nucleus undergoing alpha decay:
210 84 Po --> 206 82 Pb + 4 2 He
“4 2 He” represents the alpha particle
**The mass number changes by 4 in alpha decay and the atomic number changes by 2.
For the following quiz, review the above summary to assist you in answering the question. Select the best choice from the given answers.
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