1 nuclear chemistry why do some atoms undergo nuclear changes?

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  • *RadioactivityEmission of particles and/or energy due to a change in the nucleus of an atom.Nuclear Radiation also called Ionizing radiationMeasure with Geiger Counter

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    Geiger Counter: Radiation detection

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    IsotopesHydrogen: 11H, protium21H, deuterium31H, tritium (radioactive)Helium, 42HeLithium, 63Li and 73LiBoron, 105B and 115BExcept for 11H the mass number is always at least 2 x atomic number.

    Repulsive forces between protons must be moderated by neutrons.

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    IsotopesSame element (Z) but different mass number (A).Boron-10 has 5 p and 5 n: 105B

    Boron-11 has 5 p and 6 n: 115B

    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Why do unstable isotopes undergo nuclear reactions?Unstable isotopes undergo nuclear reactions so that they may be changed, or transformed, into stable isotopes.

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    Stability of Nuclei Heaviest naturally occurring non-radioactive isotope is 209Bi with 83 protons and 126 neutrons There are 83 x 126 = 10,458 possible isotopes. Why so few actually exist?

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    Band of Stability and Radioactive DecayIsotopes with a n/p ratio, below or above the band of stability decay, by various nuclear reactions.

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    Stability of Nuclei Out of > 300 stable isotopes:EvenOddOddEvenZN15752505

    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Types of RadiationTypes of Radiation

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Types of RadiationRadiation is emitted during radioactive decay.Three types of nuclear radiation are alpha radiation, beta radiation, and gamma radiation.

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    Types of NUCLEAR Radiation

    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Types of RadiationAlpha RadiationSome radioactive sources emit helium nuclei, which are also called alpha particles.The electric charge is usually omitted.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Alpha RadiationThe radioisotope uranium-238 emits alpha radiation and is transformed into another radioisotope, thorium-234.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Alpha RadiationWhen an atom loses an alpha particle, the atomic number of the product is lowered by two and its mass number is lowered by four.In a balanced nuclear equation, the sum of the mass numbers (superscripts) on the right must equal the sum on the left.The same is true for the atomic numbers (subscripts).

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Alpha RadiationBecause of their large mass and charge, alpha particles do not travel very far and are not very penetrating.A sheet of paper or the surface of your skin can stop them.But radioisotopes that emit alpha particles can cause harm when ingested.Once inside the body, the particles dont have to travel far to penetrate soft tissue.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Beta RadiationAn electron resulting from the breaking apart of a neutron in an atom is called a beta particle.The neutron breaks apart into a proton, which remains in the nucleus, and a fast-moving electron, which is released.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Beta RadiationThe 1 represents the charge on the electron.The 0 represents the extremely small mass of the electron compared to the mass of a proton.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Beta RadiationThe nitrogen-14 atom has the same mass number as carbon-14, but its atomic number has increased by 1.It contains an additional proton and one fewer neutron.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Beta RadiationA beta particle has less charge than an alpha particle and much less mass than an alpha particle.Thus, beta particles are more penetrating than alpha particles.Beta particles can pass through paper but are stopped by aluminum foil or thin pieces of wood.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Beta RadiationBecause of their opposite charges, alpha and beta radiation can be separated by an electric field.Alpha particles move toward the negative plate.Beta particles move toward the positive plate.Gamma rays are not deflected.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Gamma RadiationA high-energy photon emitted by a radioisotope is called a gamma ray.The high-energy photons are a form of electromagnetic radiation.Gamma rays are emitted during radioactive decay.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Types of RadiationGamma rays have no mass and no electrical charge.Emission of gamma radiation does not alter the atomic number or mass number of an atom.Gamma Radiation

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Gamma rays are extremely penetrating making them dangerous.Gamma rays pass easily through paper, wood, and the human body.They can be stopped, although not completely, by several meters of concrete or several centimeters of lead.Gamma Radiation

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    Penetrating Ability

    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Gamma rays can be dangerous because of their penetrating power. What property determines the relative penetrating power of electromagnetic radiation?CHEMISTRY & YOUThe wavelength and energy of electromagnetic radiation determine its relative penetrating power. Gamma rays have a shorter wavelength and higher energy than X-rays or visible light.

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Interpret Data

    Characteristics of Some Types of RadiationTypeConsists ofSymbolChargeMass (amu)Common sourcePenetrating powerAlpha radiationAlpha particles (helium nuclei) a, 2+4Radium-226Low (0.05 mm body tissue)Beta radiationBeta particles (electrons) b,11/1837Carbon-14Moderate (4 mm body tissue)Gamma radiationHigh-energy electromagnetic radiation g00Cobalt-60Very high (penetrates body easily)

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Which process involves a radioactive nucleus releasing a high-speed electron?A.oxidationB.alpha emissionC.beta emissionD.gamma radiationC

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Radioactivity

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    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. Radioactivity

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    Nuclear ReactionsErnest Rutherford found Ra forms Rn gas when emitting an alpha particle.

    1902Rutherford and Soddy proposed radioactivity is the result of the natural change of the isotope of one element into an isotope of a different element.

  • *Nuclear ReactionsorTransmutationsNatural DecaySpontaneous breakdown of unstable nuclei. Called Radioisotopes

  • *NATURAL Decay:DECAY = Fall apartAlpha DECAYBeta DECAYPositon DECAY

    25.1 Nuclear Radiation >*

    Copyright Pearson Education, Inc., or its affiliates. All Rights Reserved. RadioactivityRadioactive decay is a spontaneous process that does not require an input of energy.If the product of a nuclear reaction is unstable, it will decay too.The process continues until unstable isotopes of one element are changed, into stable isotopes of a different element.Stable isotopes are not radioactive.

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