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CHEMICAL  REACTIONS:  
 
 
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 Substances  can  always  be  broken  down  into  smaller  pieces  of  the  
same  substance
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 J
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Each  dynamide  is  made  up  of  a  positively  charged  particle  and  a  negatively  
charged  particle
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-­‐ Ernest  Rutherford  
 
Planetary  Model-­‐  Atoms  are  made  up  of  a  solid,  positively  charged  nucleus  
surrounded  by  electrons  orbiting  the  nucleus  like  planets  orbiting  the  sun
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 The  nucleus  is  surrounded  by  electrons  orbiting  it  
like  planets  orbit  the  sun
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 The  electrons  form  shells  around  the  nucleus
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Recall  that  all  matter  is  composed  of  atoms  and  has  mass  
 
Matter  is  everything  around  you
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 Matter  is  anything  that  has  mass  and  takes  up  space
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 ]  surrounding  a  
nucleus  [nucleus:  The  central  part  of  an  atom
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 ]  that  contains  protons  
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 and  neutrons  
,neutrons:  Uncharged  sub-­‐atomic  particles,  with  a  mass  of  1  relative  to  a  proton
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Protons  have  a  relative  charge  of  +1,  while  electrons  have  a  relative  charge  
of  -­‐1
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 In  the  
periodic  table  atoms  are  arranged  in  atomic  number  order
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 The  electronic  structure  of  
an  atom  is  a  description  of  how  the  electrons  are  arranged,  which  can  be  
shown  in  a  diagram  or  by  numbers
...
 
The  structure  of  an  atom  
 
Although  the  word  'atom'  comes  from  the  Greek  for  indivisible,  we  now  know  
that  atoms  are  not  the  smallest  particles  of  matter
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At  the  centre  of  an  atom  is  a  nucleus    containing  protons  and  neutrons
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Both  protons  and  electrons  have  an  electrical  charge
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 The  
neutron  is  neutral
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 This  means  atoms  have  no  overall  electrical  charge
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 Also  called  the  proton  number
...
   
 
Energy  levels  and  shells  
Electrons  are  arranged  in  different  shells  around  the  nucleus
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 Each  succeeding  shell  can  only  hold  a  
certain  number  of  electrons  before  it  becomes  full
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The  table  gives  the  maximum  capacity  of  the  first  three  shells
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 Two  are  in  the  first  energy  
level,  and  one  in  the  second
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 Two  are  in  the  first  energy  level,  and  four  in  the  
second  energy  level
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 For  your  exam,  you  need  to  be  able  to  describe  the  electronic  structure  
of  the  first  20  elements  in  the  periodic  table
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 Their  
electronic  structures  can  be  shown  either  as  diagrams  or  numbers
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Take  lithium,  for  example
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 The  numerical  
method  is  to  write  the  chemical  symbol  (Li  )  followed  by  the  number  of  electrons  
in  each  energy  level,  innermost  first,  Li  2,1
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Group  1  
Two  of  these  fit  into  the  first  energy  
level,  with  the  third  in  the  second  
energy  level
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 Remember  -­‐  you  need  to  learn  the  
electronic  structures  of  the  first  20  elements
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Electronic  structures  of  elements  
Element  
Numeric  
Electrons  
Periodic  

format  
F  2,7  

   

 
Ne  2,8  

   

 
Na  2,8,1  

   

table  group  
Fluorine  atoms  have  nine  electrons
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 The  remaining  seven  fit  into  the  
second  energy  level
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 Two   Group  0  -­‐  
of  these  fit  into  the  first  energy  level
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 Because  its  
highest  occupied  energy  level  is  full,  
neon  is  stablestable:  Atoms  are  stable  
if  their  outer  shell  contains  its  
maximum  number  of  electrons
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Sodium  atoms  have  11  electrons
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The  last  one  fits  into  the  third  energy  
level
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Two  of  these  fit  into  the  first  energy  
level,  eight  into  the  second  energy  
level,  another  eight  into  the  third  
energy  level
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Electronic  structure  and  the  periodic  table  
As  you  have  seen,  there  is  a  link  between  an  atom's  electronic  structure  and  its  
position  in  the  periodic  table
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Group  2  

Periodic  table  related  to  electronic  structure  
 
The  diagram  shows  a  section  of  the  periodic  table,  with  the  elements  arranged  as  
usual  in  the  order  of  their  atomic  number,  from  2  to  20
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Moving  across  each  period,  you  can  see  that  the  number  of  occupied  energy  
levels  is  the  same  as  the  period  number
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 The  highest  occupied  energy  level  contains  just  
one  electron  on  the  left-­‐hand  side  of  the  table
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Moving  down  each  group,  you  can  see  that  the  number  of  electrons  in  the  
highest  occupied  energy  level  is  the  same  as  the  group  number
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 Group  0  is  a  partial  exception  to  this  rule
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Working  out  an  element's  electronic  structure  
Here  is  how  to  use  the  periodic  table  to  work  out  an  electronic  structure:  
1 Find  the  element  in  the  periodic  table
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2 Work  out  which  group  the  element  is  in  and  draw  that  number  of  
electrons  in  the  outer  circle  -­‐  with  eight  for  Group  0  elements  -­‐  except  
helium
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 Remember  -­‐  two  in  the  first,  eight  in  
the  second  and  third,  and  18  in  the  fourth
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Material  used  
Hazard/risk  
How  to  minimize  the  risk  
 
 
 
 
 
 
 
 
 
 
 
 
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 They  are  
arranged  into  columns  and  rows
...
 
 
Atomic  number-­‐  Represents  the  number  of  protons  found  in  the  nucleus,  which  
in  an  atom  is  equal  to  the  number  of  electrons  outside  the  nucleus  
 
Mass  number-­‐  Represents  the  total  number  of  protons  and  neutrons  found  in  
the  nucleus  
 
Number  of  electrons  =  Number  of  protons  in  an  atom  
Number  of  neutrons  =  Mass-­‐  atomic  number  
 
Key  things  to  remember  about  the  subatomic  particles:  
 
• The  atomic  number  of  an  atom  is  the  number  of  positive  protons  in  the  
nucleus;  it  determines  the  element  of  the  atom  
• Neutrons  are  also  found  in  the  nucleus  but  have  no  charge  
• The  mass  number  of  an  atom  is  the  combined  number  of  protons  and  
neutrons  
• Electrons  are  negatively  charged  
• An  atom  has  the  same  number  of  electrons  as  protons  
• Protons-­‐  Particles  with  a  positive  charge  and  about  the  same  mass  as  a  
neutron  
• Neutrons-­‐  Particles  with  no  charge  and  about  the  same  mass  as  a  proton  
• Electrons-­‐  Particles  with  a  negative  charge  and  a  mass  of  1/1840  that  of  
a  proton  or  neutron  
 

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Some  signs  that  a  chemical  reaction  has  occurred  could  include:  
1) Formation  of  gas  
2) Formation  of  precipitate  
3) Liberation  or  absorption  of  heat,  light,  or  some  form  of  energy  
4) Distinct  change  in  colour  
 
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g  
Silver  nitrate  and  potassium  iodide  =  Silver  nitrate  (aq)  +  potassium  iodide  (aq)  
>  silver  iodide  (s)  +  potassium  nitrate  (aq)  
 
e
...
 Copper  sulphate  +  sodium  hydroxide  =  Copper  sulphate  (aq)  +  sodium  
hydroxide  (aq)  >  copper  hydroxide  (s)  +  sodium  sulphate  (aq)  
 
 
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"  
 
Law  of  Conservation  of  Mass  -­‐  No  detectable  gain  or  loss  in  mass  occurs  in  
chemical  reactions
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 For  example,  substances  involving  in  a  chemical  reaction  can  change  
from  solid  states  to  gaseous  states  but  the  total  mass  will  not  change
...
 
 
4 What  is  the  Law  of  Conservation  of  Mass?  
5 When  elements  and  compounds  react  to  form  new  products,  mass  cannot  
be  lost  or  gained
...
 
7 So,  in  a  chemical  change,  the  total  mass  of  reactants  must  equal  the  
total  mass  of  products
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Describe  decomposition  reactions  as  the  breaking  down  of  
compounds  into  2  or  more  substances  

 
Decomposition  reactions-­‐  These  are  reactions  in  which  a  substance  is  broken  
down  into  smaller  products
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g
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Define  a  precipitation  reaction  as  one  in  which  an  insoluble  solid  is  
produced  
-

In a precipitation reaction a product of the reaction is only slightly
soluble, or insoluble
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-

Precipitation reactions occur when cations and anions in aqueous
solution combine to form an insoluble ionic solid called a precipitate
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Describe  corrosion  as  a  chemical  reaction  between  a  metal  and  
oxygen  in  its  environment  to  form  a  metal  oxide  
 
- Corrosion  is  a  natural  process,  which  converts  refined  metal  to  their  more  
stable  oxide
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 In  the  most  common  use  of  the  
word,  this  means  electrochemical  oxidation  of  metal  in  reaction  with  an  
oxidant  such  as  oxygen
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 Water  +  oxygen  
must  be  present  for  rusting  to  occur
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Identify  that  chemical  reactions  involve  energy  transfer  and  can  be  
exothermic  or  endothermic  

 
Exothermic-­‐  Energy  can  be  released  from  the  reaction  into  the  outside
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• In  an  exothermic  reaction  the  temperature  of  the  outside  goes  up  
(increases)
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 This  is  
an  endothermic  reaction  
 
Exothermic-­‐  An  exothermic  reaction  is  a  chemical  reaction  that  releases  energy  
by  light  or  heat
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Endothermic-­‐  In  thermodynamics,  the  term  endothermic  process  describes  a  
process  or  reaction  in  which  the  system  absorbs  energy  from  its  surroundings;  
usually,  but  not  always,  in  the  form  of  heat
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Identify  the  products  and  reactions  of  combustion  reactions  
 
-­‐Combustion  is  a  chemical  process  in  which  a  substance  reacts  rapidly  with  
oxygen  and  gives  off  heat
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 The  fuel  can  be  a  solid,  liquid,  or  gas,  
although  for  airplane  propulsion  the  fuel  is  usually  a  liquid
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Describe  how  to  test  for  oxygen  using  a  glowing  splint  and  hydrogen  
using  a  lit  splint  and  the  results  obtained  if  a  gas  is  present  
 
Hydrogen  
To  test  for  hydrogen  a  small  sample  can  be  ignited
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Hydrogen  reacts  very  quickly  with  oxygen  to  form  water
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This  is  a  simple  but  effective  test  for  oxygen
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 A  hydrogen  pop  is  much  more  violent,  sometimes  
enough  to  completely  extinguish  the  splint
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Compare  combustion  and  respiration  as  types  of  chemical  reactions  
that  release  energy  but  occur  at  different  rates  
 
Respiration  and  combustion  are  2  reactions  that  are  the  same  but  different:  
 
COMBUSTION  :  
 
-­‐ Combustion-­‐  Reaction  of  an  element  or  a  compound  with  oxygen  and  
produce  heat
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-­‐Combustion  is  a  chemical  process  in  which  a  substance  reacts  rapidly  with  
oxygen  and  gives  off  heat
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 The  fuel  can  be  a  solid,  liquid,  or  gas,  
although  for  airplane  propulsion  the  fuel  is  usually  a  liquid
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-­‐ Cellular  respiration  is  the  process  of  oxidizing  food  molecules,  like  
glucose,  to  carbon  dioxide  and  water
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-­‐Energy  is  released  very  slowly  
 
INSIDE  YOUR  CELL  
Glucose  +  Oxygen  >  carbon  dioxide  +  water  +  energy  
-­‐If  you  burn  energy  in  the  outside  (in  the  lab),  it  is  called  combustion  
 
 
 
 
 
 
 
 
 
 
 
 
 

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• The  nitrogen  cycle-­‐  the  series  of  processes  by  which  nitrogen  and  its  
compounds  are  interconverted  in  the  environment  and  in  living  
organisms,  including  nitrogen  fixation  and  decomposition
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• The  Carbon  cycle-­‐ the  series  of  processes  by  which  carbon  compounds  
are  interconverted  in  the  environment,  involving  the  incorporation  of  
carbon  dioxide  into  living  tissue  by  photosynthesis  and  its  return  to  the  
atmosphere  through  respiration,  the  decay  of  dead  organisms,  and  the  
burning  of  fossil  fuels
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 The  compounds  change  into  different  ones  by  
exergonic  reactions
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Chemical engineer
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Forensic scientist
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Research scientist (physical sciences)
Toxicologist

Chemistry improves almost all aspects of people's lives either directly or
indirectly; advances in chemistry have led to life-saving medicine,
improvements to the way humans treat their environment, sources of green
energy and other useful technologies
...

 



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