CHAPTER24CHEM

CHAPTER24CHEM -...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 24 Nuclear Reaction and Their Applications “24.1 Radioactive Decay and Nuclear Stability” Nuclei: plural of nucleus (many nucleuses) The great majority of nuclei are unstable. An unstable nucleus exhibits radioactivity: it spontaneously decays by emitting radiation. Protons (+) and neutrons (neutral), the elementary particles that make up the nucleus, are called nucleons. A nuclide is a nucleus with specific numbers of the two types of nucleons. Most elements occur in nature as a mixture of isotopes , atoms w/ the same # of protons of the element but diff. numbers of neutrons. Each isotope of an element is particular nuclide that we identify by its protons and neutrons. A Z X X is the symbol for the particle, A-mass # (top) is mass number (sum of protons and neutrons), Z-atomic # is charge of particle (# of protons). The number of neutrons (N) is mass # A - atomic # Z. N= A-Z nuclides can be written as element name followed by mass #, ex. Chlorine-35, or chlorine-37 Particle: atom, ion, or molecule When a nuclide of one element decays, it emits radiation, and under most circumstances, changes into a nuclide of a diff. element. Three natural types of radioactive emission are: - alpha particles  :  α are identical to helium-4 nuclei. - beta particles β are high-speed electrons. - gamma rays ɣ : are very high-energy photons (a quantum(indivisible amount) of electromagnetic radiation) When a nuclide decays, it forms a nuclide of lower energy, and the excess energy is carried off by the emitted radiation and the recoiling nucleus. The reactant nuclide (one that gets decayed) is called the parent , the product nuclide is the daughter . Key principle for balancing nuclear reactions: the total Z (charge, # of protons) and the total A (sum of protons and neutrons) of the reactants equal those of the products: Total A Total Z Reactants = Total A Total Z Products Types of Decay: 1. Alpha ( α ) decay: involves loss of an alpha particle from a nucleus. For each alpha particle emitted by the parent (reactant), A (atomic mass, protons + neutrons) decreases by 4 and Z (atomic mass, # of protons) decreases by 2 in the daughter (product). Every element beyond bismuth (Bi; Z=83) is radioactive and exhibits alpha decay. So, alpha decay is the most common means for a heavy, unstable nucleus to become more stable. Ex. Radium (Rn) undergoes alpha decay to yield radon (Rn; Z=86) : 226 88 Ra 222 86 Rn + 4 2    ( A: α 226 222+4 ; Z: 88 86+2) 2. Beta ( ) β decay: general class of decay that includes 3 types: β -  decay,  β +  emission, and electron capture.  β - decay  :  involves the ejection of a β  -   particle from the nucleus: a neutron is converted into a proton, which remains in the nucleus, and a β  -    particle is expelled immediately : 1 0 n 1 1 p + 0 -1                                   β 14 6 C 14 7 N + 0   -1    again, total A and Z of reactants equals products
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/14/2010 for the course CHEM 1A taught by Professor Okamura during the Fall '08 term at UC Riverside.

Page1 / 4

CHAPTER24CHEM -...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online