Patterns+of+Nuclear+Stability

=__ 21.2 __=

Neutron-to-Proton Ratio

 * Empirical observations is the key when predicting the stability of nucleus
 * Nuclear force: strong force of attraction
 * Atomic Numbers up to 20 have stable nuclei (same amounts of protons and neutrons)
 * Atomic Numbers greater than 20 have more neutrons than protons.
 * The ratio of neutron / proton increases as the atomic number increases.
 * Nuclei that has more than 84 protons are said to be radioactive.

Three general situations: 1. Nuclei that has more neutrons than protons can move closer to the belt of satbility by emitting a beta particles. This process decreases the number of Nuetrons but increases the number of prtons. 2. Nuclei that has less neutrons than protons can increase their ratio by either positron emission or electron capture. Positron emission is when a proton is converted into neutron and a positron (an anti electron that ejects out). 3. Nuclei whose atomic number is greater than or equal to 84 that lie beyond the upper right edge of the band of stability. They undrego alpha emission in which particles decreases both the number of neutrons and protons by 2 movie it towards the stability line.

Radioactive sereies



 * Radioactive series are series that start with an unstable nucleus which subsequently decays until it achieves a stable nucleus.
 * This is also called nuclear disintegration series.

** Further Observations: **

 * Magic numbers: Protons (2,8,20,28,50,82), neutrons (2,8,20,28,50,82,126).
 * The nuclei with these magic numbers are more stable than other nuclei that do not contain these numbers
 * Nuclei with even numbers of protons and neutrons are more stable
 * Shell model of the nucleus - a nuclear model in which protons and neutrons exist in levels, or shells, analogous to the shell structure that exists for electrons in an atom.



Need more help?

[]

[]

[]

References:

Brown, Theodore L., H. Eugene LeMay, and Bruce Edward. Bursten. // Chemistry the Central Science //. Upper Saddle River, NJ: Prentice Hall, 2002. Print.

"Radioactive Series @ Chemistry Dictionary & Glossary." // Croatian-English Chemistry Dictionary & Glossary | Englesko-hrvatski Kemijski Rječnik & Glosar //. Web. 23 Mar. 2011. .