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Introduction to Nuclear Chemistry 
RADIATION  ​is  energy  given  off  by  matter  in  the  form  of 
rays or high-speed particles 

 
 
COMPARISON OF CHEMICAL & NUCLEAR 
REACTIONS 

 

WHAT IS RADIOACTIVITY? 
Radioactive  decay occurs in unstable atomic nuclei-that 
is  one  that  don’t  have  enough  binding  energy  to  hold 
the  nucleus  together  due  to  an  excess  of  either protons 
or neutrons
...
 

●

 

EARLY PIONEERS IN RADIOACTIVITY: 
Wilhelm Roentgen (1895) ​— discovered X
​ -rays 
Henri Becquerel (1896) ​— discovered r​ adioactivity 
Ernest  Rutherford  (1897)  ​—  discovered  ​alpha  and  beta 
rays  
Marie  Curie  ​and  ​Pierre  Curie (1900 - 1908) ​— identified 
two new elements,​radium a​ nd ​polonium  

Ernest  Rutherford  ​identified  alpha,  beta,  and  gamma 
radiation  when  studying  the  effects  of  an  electric  field on 
the emissions from a radioactive source: 
● The  effect  of  an  electric  field  depends  on  the  charge 
and mass of the radiation 
● Positively  charged  alpha  particles  deflect  toward  the 
negative plate 
● Negatively  charged  beta  particles  deflect  toward  the 
positive plate 
● Gamma  rays  have  no  charge  and  are  not  affected  by 
an electric field 
 
CHEMICAL REACTIONS: 
● the compositions of the atomic nuclei remain 
unchanged 
● atoms rearrange and/or transfer electrons from one 
element to another 
 

NUCLEAR REACTIONS:  
● involve changes in the composition of the atomic 
nuclei 
● the changes result in changes in the number of 
protons in the nuclei; changing the identity of the 
elements 
● focus on protons and neutrons (also called nucleons) 
in the nucleus 

●

occur when bonds are 
broken and formed 
involve only valence 
electrons 
associated with small 
energy changes 
atoms keep the same 
identity although they 
might gain, lose, or 
share electrons, & form 
new substances  

Nuclear Reactions 
●

●
●
●

occur when nuclei 
combine, split & emit 
radiation 
can involve protons, 
neutrons & electrons 
associated with large 
energy changes 
atoms of one element 
are often converted into 
atoms of another 
element  

 
SUMMARY: 
● As  an  unstable  atom  tries  to  reach  a  stable  form, 
energy and matter are released from the nucleus
...
 
● When  there  is  a  change  in  the  nucleus  and  one 
element  changes  into  another,  it  is  called 
transmutation​
...
 
● All  nuclei  outside  the  band  of  stability  –  either 
above or below – are radioactive and undergo decay 
in order to gain stability
...
  These  unstable  nuclei  emit  radiation  to  attain 
more  stable  atomic  configuration  in  a  process  called 
radioactive  decay​
...
Alpha ( α ) 
2
...
Gamma ( γ ) 

Introduction to Nuclear Chemistry 
 
ALPHA PARTICLES: 
● An  alpha  particle  (α)  has  the same composition as a 
helium  nucleus—two  protons  and  two  neutrons 
—and is therefore given the symbol ​4​2​He 
○ Its  charge  is  2+  due  to  the  presence  of  the 
two protons 
● Alpha  radiation  consists  of  a  stream  of  alpha 
particles 
○ Because  of  their  mass  and  charge,  alpha 
particles  are  relatively  slow-moving 
compared with other types of radiation 
BETA PARTICLES: 
● A beta particle is a very fast-moving electron  
● Beta particles are represented by the symbol β or e 
● They have a 1– charge 
● Beta  radiation  consists  of  a  stream  of  fast-moving 
electrons  

 
TYPES OF RADIOACTIVE EMISSIONS: 
1
...


PENETRATING  POWER:  ​the  ability  of  radiation  to 
pass through matter  
● Alpha particles h
​ ave a low penetrating power 
○ they move slowly due to their large mass 
○ their  2+  charge  causes  them  to  lose  energy 
quickly  through  interactions  with  other 
particles 
○ may  be  completely  stopped  by  a  sheet  of 
paper  
● Beta particles h
​ ave a higher penetrating power 
○ they  are  smaller  and  faster  than  alpha 
particles 
○ they can still interact with particles and can 
be stopped by thin shielding 
○ may  be  completely  stopped  by  aluminum 
shielding 
● Gamma rays a
​ re highly penetrating 
○ they have no charge and no mass 
○ the  probability  of  matter  stopping  them  is 
low 
○ they  can  only  be  reduced  by  much  more 
substantial  obstacles,  such  as  a  very  thick 
piece of lead
...


 

Gamma Emission 
● Because  photons  have  no  mass  and  no  charge, 
the emission of gamma rays does not change the 
atomic number or mass number of a nucleus 

TO SUMMARIZE: 
● Gamma rays are electromagnetic radiation— 
high-energy, short-wavelength photons 
● Gamma rays have the symbol γ 
● Gamma rays have low ionizing power 
● Gamma rays have high penetrating powers 
 
4
...


Radioactive 
Decay 

 
Electron Capture 
● occurs  when  the  nucleus  of  an  atom  draws  in  a 
surrounding  electron,  usually  one  from  the 
lowest energy level 
○ This  captured  electron  combines  with  a 
proton to form a neutron  
● As  a  consequence  of  electron  capture,  the 
atomic number o​ f the nucleus decreases by ​1  
● The  formation  of  the  neutron  also  results  in  an 
X-ray photon being emitted 
 

 



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