Observations of Nuclear stability ►►► 01. In the plot [Look at the diagram] , y axis is number of neutrons and the x axis is the number of protons. The red graph is 1:1 n : p line. Light blue band is known as zone of stability and the nu...See More Photo: Observations of Nuclear stability ►►► 01. In the plot [Look at the diagram] , y axis is number of neutrons and the x axis is the number of protons. The red graph is 1:1 n : p line. Light blue band is known as zone of stability and the nuclei in this zone are stable. From the band, to the side of Y axis, there are too many neutrons and undergo β decay. From the band, to the side X axis, there are too many protons and undergo positron emission or electron capture. 02. Elements from Z> 84 (from Polonium) unstable with respect to radioactivity. 03. Light nuclei are stable when the number of protons are equal to number of neutrons. Ex: 4-He 2, 6 – Li 3, 16 – O 8, 12 – C 6 04. As the number of protons increased then the n/p increases with atomic number. 56 – Fe 26, has 26 protons and 30 neutrons. This is because of, more neutrons are needed to stabilize. 05. There are certain combinations of p and n which seems to confer special stabilities. • Even – even combination shows extra stability. Number of proton Number of neutron Number of stable nuclei Even Even 168 Even Odd 57 Odd Even 50 Odd Odd 4 • Out of 2000+ known nuclei, only 279 are stable. 06. Certain specific number of proton or neutron, which produces stable nuclides. Those are called as MAGIC NUMBERS. The magic numbers are, 2, 8, 20, 28, 50, 82 and 126 Ex: 4 – He 2, 16 – O 8, 40 – Ca 20, 208 – Pb 82 208 – Pb 82 is the last stable isotope in the periodic table.
Posted on: Sat, 27 Jul 2013 12:25:31 +0000
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