Atoms and Molecules (Chapter 8)

• Atoms


  -Different elements in size

  -Simplest substance which cannot be broken down any further

  -Substance consisting of 1 type of atom only
• Protons

  Mass: 1

  Charge: Positive , (+1)
• Electron

  Mass: 1/1840

  Charge: Negative, (-1)
• Neutron

  Mass: 1

  Charges: Neutral, (0)
• Atoms are electrically neutral because...

  the number of protons= the number of electrons
• Proton numbers are the number of protons in an atom
• Nucleon number= Protons + Neutrons in an atom
• Molecules


  -2 or more atoms chemically combined together

  
  

  -Molecule of an element is a substance which contains 2 or more atoms of the same type

  [Examples: Hydrogen(H2), Oxygen(O2), Phosphorous(P4)]

  
  

  -Molecule of a compound is a substance which contains 2 or more atoms of different types

  [Examples: Hydrogen chloride (HCL), Water (H2O), Methane (CH)]
• Ions

  -Atoms with electrical charges

  -When an atom loses electrons (-), it becomes a positively charged ion

  -When an atom gains electrons, it becomes a negatively charged ion

  -The value of charges depend on the number of electrons loss/gained
• (-)


  electrons
• (+)

  protons
• ( )

  neutrons