Lect14 -- Nuclear Principles

Nucleus held together by the strong force puzzle 1

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Unformatted text preview: ly charged protons, but we know that like charges repel each other… so why doesn’t the nucleus fall apart? •  Nucleus held together by the “STRONG FORCE” Puzzle #1: what could possibly lower the mass of 12C so that it is 12.000000 a.m.u.? •  Strong force means there is a binding energy holding the nucleus together – separating the protons and neutrons would require a defined energy input •  Energy is equivalent to mass: E = mc2 •  So total mass left after separating the n, p, and e from 12C also must account for the energy required to split these! Isotopes A nucleus has a definite number of protons (Z), a definite number of neutrons (N) with atomic number A = Z + N Elements have a defined number of protons (Z) Isotopes of an element have same Z, differing numbers of neutrons (so different N and thus also A) For example, take the element carbon: the most common isotope of carbon has 6 protons and 6 neutrons (denoted 12C; 98.9% abundance) Z = 6; N = 6; A = 12 another stable isotope of carbon has 6 protons and 7 neutrons (denoted 13C; 1.1% abundance) Z = 6; N = 7; A = 13 an unstable isotope of carbon has 6 protons and 8 neutrons (denoted 14C; half-life is 5730 years) More examples of isotopes Fission of uranium •  Barium and krypton r...
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This document was uploaded on 12/05/2013.

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