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 9038Sr 86

36Rn + 42He

Chemical equation KClO3 (s) 2KCl (s) + O2 (g)

Physical change equation CO2 (s) CO2 (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- H2O2)H2O + Na NaOH + H2

3)NaCl (s) Na+ (aq) + Cl- (aq)4)4He + 12C 16N + 0n

Alpha particle 42He α

•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 0-1e β

•Similar to a high speed electron•Has a mass of 0 and a charge of -1

Positron 0+1e

•Commonly known as an electron catcher•Has a mass of 0 and a charge of +1

Gamma radiation 00γ

•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 10n

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

Symbol Mass Charge Penetrating power

Able to be accelerated

Alpha 42He, α 4 amu +2 Low

(weakest)Yes

Beta 0-1e, β 0 amu -1 Medium Yes

Positron 0+1e, +β 0 amu +1 Medium Yes

Gamma 00γ 0 amu 0 High

(strongest)No

Neutron 10n 1 amu 0 ------- 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-28 2814Si Francium-223 223

87Fr STABLE UNSTABLE

1:1 neutron to proton ratio 1.5:1 neutron to proton ratio

14p14 n

87 p137 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) 32P 2) 14C 3) 239Pu 4) 3H

Alpha decay is when a radioactive nucleus spontaneously breaks down to emit an alpha particle (4

2He)

23892U 4

2He + 23490

Th

Radioactive atom238

92UNew atom formed after decay 234

90Th

Mass number 238 234

Number of protons (atomic #)

92 90

Number of neutrons (mass # - atomic #)

146 144

Mass number is decreased by 4Number of protons (atomic number) is decreased by 2Number of neutrons is decreased by 2

To determine which equation represents alpha decayLOOK 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)19

10Ne 1911Na + 0

-1e2)228

89Ac 22888Ra + 0

+1e3)232

90Th 4

2He + 22888Ra

4)22087Fr + 42He 224

89Ac

Beta decay is when a radioactive nucleus spontaneously breaks down to emit (release) a beta particle 0

-1e

146C 0

-1e + 147N

Radioactive nucleus14

6CNew element formed14

7N

Mass number (nucleons)

14 14

Number of protons (atomic #)

6 7

Number of neutrons (mass # - atomic #)

8 7

Mass number remains the sameNumber of protons (atomic number) is increased by 1Number of neutrons is decreased by 1

To determine which equation represents a beta decayLOOK 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) 1910Ne 19

11Na + 0-1e

2) 22889Ac 228

88Ra + 0+1e

3) 23290

Th 42He + 228

88Ra4) 22087Fr + 4

2He 22489Ac

Positron emission occurs when an atom emits (releases) a positron 0

+1e as it decays

3720Ca 0

+1e + 3719K

Radioactive nucleus37

20CaNew element formed37

19K

Mass number (nucleons)

37 37

Number of protons (atomic number)

20 19

Number of neutrons(mass # - atomic #)

17 18

After a positron emission:Mass number remains the sameNumber of protons (atomic number) is decreased by 1Number of neutrons is increased by 1

To determine which equation represents a positron emissionLOOK 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)19

10Ne 1911Na + 0

-1e2)228

89Ac 22888Ra + 0

+1e3)232

90Th 4

2He + 22888Ra

4)22087Fr + 4

2He 22489Ac

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

42He + 9

4Be 126C + 1

0n

To identify artificial transmutation equationsLOOK for an equation with TWO particles on the

LEFT and TWO particles on the RIGHT

1)Which equation is showing an artificial transmutation?

1910Ne 19

11Na + 0-1e

2)22889Ac 228

88Ra + 0+1e

3)23290

Th 42He + 228

88Ra4)22087Fr + 4

2He 22489Ac