Nuclear chemistry is the study of changes that occur in the nucleus of atoms Nucleus Protons and neutrons are found in nucleus Number of protons determines the identity (atomic number) of the atom Number of neutrons determines the mass number of the atom Any change to the nucleus of an atom involves changes to the number of protons and/or neutrons Any change to the nucleus of an atom will always change that atom to become a different atom Transmutation is the changing (converting) of one atom to another by nuclear changes

Nuclear transmutation occurs when one nucleus is changed into another A nucleus can release a particle (proton, neutron, alpha, positron, and/or electron) A nucleus can absorb a particle A nucleus can absorb one particle,, and release another A nucleus can split into smaller nuclei A nucleus can join with another nucleus to form a larger nucleus Nuclear equations can be used to show a change of one nucleus to another

Nuclear equation Sr  Rn He Chemical equationKClO 3 (s)  2KCl (s) + O 2 (g) Physical change equationCO 2 (s)  CO 2 (g) To determine which equation is showing a nuclear change or transmutation LOOK for an equation uses nuclear symbols Which of these equations represents a nuclear change? 1)H + + OH -  H 2 O 2)H 2 O + Na  NaOH + H 2 3)NaCl (s)  Na + (aq) + Cl - (aq) 4) 4 He + 12 C  16 N + 0 n

Alpha particle 4 2 Heα Similar to a helium nucleus Has a mass of 4 amu and a charge of +2 Have the lowest penetrating power of all radiations Can be stopped by a sheet of paper Beta particle 0 -1 e β Similar to a high speed electron Has a mass of 0 and a charge of -1 Positron 0 +1 e Commonly known as an electron catcher Has a mass of 0 and a charge of +1 Gamma radiation 0 0 γ Similar to a high energy x-ray Has a mass of 0 and a charge of 0 Has the highest penetrating power of all radiations Can only be stopped by a block of lead Neutron 1 0 n

Accelerator – device that moves changed particles to a high speed Only charged particles (alpha, beta, positron) can be accelerated Penetrating power – refers to the strength of a particle to go through an object Nuclear Particle SymbolMassChargePenetrating power Able to be accelerated Alpha 4 2 He, α4 amu+2Low (weakest) Yes Beta 0 -1 e, β0 amuMediumYes Positron 0 +1 e, +β0 amu+1MediumYes Gamma 00γ00γ0 amu0High (strongest) No Neutron 10n10n1 amu No

Electric or magnetic field can be used to separate particles and radiations that are released from a radioactive source during nuclear decays Electric field contains two charged plates; positive and negative charged plates As the particles are released from a source Negative particles will be attracted to (deflected toward) the positive plates of the electric field Uncharged particles will be unaffected (not deflected) by the electric field, and will go straight through Positive particles will be attracted to (deflected toward) the negative plates of the electric field

Most elements are stable and do not undergo spontaneous decay in their natural state What determines if an element is stable or unstable in its natural state? Ratio of neutrons to protons in the nucleus determines stability The lower the ratio of neutrons to protons, the more stable the element The higher the ratio of neutrons to protons, the more unstable is the element Elements with 1:1 ratio of neutrons to protons are the most stable Elements with atomic number less than 83 are all stable because they have a low neutron to proton ratio – ratio is within the belt of stability Elements with atomic number 83 and above are all unstable because they have high neutron to proton ratio – elements in their natural state spontaneously decay through natural transmutation Silicon Si Francium Fr STABLEUNSTABLE 1:1 neutron to proton ratio 1.5:1 neutron to proton ratio 14p 14 n 87 p 137 n

Natural transmutation – single unstable radioactive spontaneously changes by decaying Alpha decay, beta decay, positron emission Elements with atomic number 83 and above spontaneously decay in their natural states Elements with atomic number 82 and below must be made radioactive first before they can spontaneously decay Artificial transmutation – stable nonradioactive nucleus absorbs a article to form an unstable (radioactive) nucleus

Decay mode refers to the type of radiation that a radioisotope will release as it decays Radioisotope is any radioactive isotope of an element Alpha emitter – radioisotope that decays by releasing an alpha particle (Fr-220; U-238) Beta emitter – radioisotope that decays by releasing a beta particle (Co-60; Sr-90) Positron emitter – radioisotope that decays by releasing a positron (Fe-53; Ne-19)

To determine which radioisotope is an alpha, beta, or positron emitter LOOK at reference Table N Which radioisotope decays by releasing a particle with a mass of 4? 1) 32 P2) 14 C3) 239 Pu4) 3 H

Alpha decay is when a radioactive nucleus spontaneously breaks down to emit an alpha particle ( 4 2 He) U  4 2 He Th Radioactive atom U New atom formed after decay Th Mass number Number of protons (atomic #) 9290 Number of neutrons (mass # - atomic #) Mass number is decreased by 4 Number of protons (atomic number) is decreased by 2 Number of neutrons is decreased by 2

To determine which equation represents alpha decay LOOK for an equation that shows one radioisotope LEFT of arrow and an alpha particle on the RIGHT Which of the following equations represents an alpha decay? 1) Ne  Na e 2) Ac  Ra e 3) Th  4 2 He Ra 4) Fr He  Ac

Beta decay is when a radioactive nucleus spontaneously breaks down to emit (release) a beta particle 0 -1 e 14 6 C  0 -1 e N Radioactive nucleus 14 6 C New element formed 14 7 N Mass number (nucleons) 14 Number of protons (atomic #) 67 Number of neutrons (mass # - atomic #) 87 Mass number remains the same Number of protons (atomic number) is increased by 1 Number of neutrons is decreased by 1

To determine which equation represents a beta decay LOOK for an equation that shows one radioisotope left of the arrow and a beta particle on the right Which of the following equations represents a beta decay equation? 1) Ne  Na e 2) Ac  Ra e 3) Th  4 2 He Ra 4) Fr He  Ac

Positron emission occurs when an atom emits (releases) a positron 0 +1 e as it decays Ca  0 +1 e K Radioactive nucleus Ca New element formed K Mass number (nucleons) 37 Number of protons (atomic number) 2019 Number of neutrons (mass # - atomic #) 1718 After a positron emission: Mass number remains the same Number of protons (atomic number) is decreased by 1 Number of neutrons is increased by 1

To determine which equation represents a positron emission LOOK for an equation that shows on radioisotope LEFT of the arrow and a positron on the RIGHT Which nuclear equation represents a positron emission by a radioactive nucleus? 1) Ne  Na e 2) Ac  Ra e 3) Th  4 2 He Ra 4) Fr He  Ac

Artificial transmutation occurs when a stable non- radioactive nucleus is bombarded (hit) with a high speed particle and is changed (transmuted) into an unstable radioisotope 4 2 He Be  12 6 C n To identify artificial transmutation equations LOOK for an equation with TWO particles on the LEFT and TWO particles on the RIGHT 1)Which equation is showing an artificial transmutation? Ne  Na e 2) Ac  Ra e 3) Th  4 2 He Ra 4) Fr He  Ac