University:
Missouri State University
Course:
CHM 170 | General Chemistry II
Academic year:

2020
Views:

31

Pages:

8
Author:

stijfdenssn

1. Begin Nuclear Chemistry HW: TBA -A nucleus is held together by a nuclear force. -The stability of a nucleus depends on its ratio of neutrons to protons. -Unstable nuclei will undergo radioactive decay to form a more stable nucleus. 130 120 110 100 90 80 Number of neutrons 40 30 20 10 0 0 10 20 30 40 Number of protons (1.5:1 ratio)Hg Belt of stability (1.4:1 ratio) Sn (1.25:1 ratio) Zr 1:1 neutron-to-proton ratio 50 60 70 80 Types of nuclear decay: a Emission (420) - in alpha decay, the nucleus emits a particle that is the same as a helium molecule. mass# = pt+n° 4 42a = He -atomic #=#pt 238920 --> 420 + 90 Th 234 ẞ Emission (1ẞ) - a beta particle is identical to an electron. In beta decay, the nucleus changes a neutron into a proton and an electron and then emits the electron. 0 146C --> -1B 14 + 147N 14 CN Positron Emission (+1ẞ) - a positron is like an electron with a positive charge. In positron emission, the nucleus changes a proton into a neutron and a positron and then emits the positron. 0 85B --> +1B 8 + 4Be 5p+ 37° 0 4p Electron Capture (e) - the nucleus captures a low energy electron and combines it with a proton to form a neutron. 189F +-1e +0.1 --> 18 80 Gamma Rays (γ) - electromagnetic radiation with no mass and no charge. Can accompany other types of decay and are the most penetrating. You can use the periodic table to predict the kind of decay an isotope will undergo: • If an isotope's mass number is greater than its atomic weight (e.g 16%C), the nucleus will try to gain protons and lose neutrons (beta decay). • If an isotope's mass number is less than its atomic weight (e.g "C), the nucleus will try to lose protons and gain neutrons (positron emission or electron capture). • Alpha emission is usually only seen in very large nuclei (atomic numbers greater than 60).

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