Atomic Structure

• Relative mass of a proton

  1

  
• Relative mass of a neutron


  about the same as that of a proton

  
• Relative mass of an electron

  1/1840

  
• Relative charge of a proton

  +1

  
• Relative charge of a neutron

  0

  
• Relative charge of an electron

  -1

  
• Neutral atoms


  same number of positive protons as negative electrons

  
• Atomic (proton) number


  the number of protons in the nucleus of an atom

  
• Subatomic particles in the nucleus

  protons and neutrons

  
• Energy Levels/Electron Shells


  The region surrounding the nucleus where electrons orbit the nucleus.

  
• Proton


  A subatomic particle that has a positive charge, defines the type of atom and that is found in the nucleus

  
• Neutron


  A subatomic particle that has no charge and that is found in the nucleus of an atom

  
• Electron


  A subatomic particle that has a negative charge and is found in electron shells, orbiting the nucleus

  
• mass number (atomic mass)


  number of protons plus the number of neutrons in an atom of an element

  
• Average atomic radius


  0.1 nm (1 x 10^-10 m)

  
• Average radius of an atomic nucleus

  10,000 times smaller than an atom (1 x 10^-14 m)
• Number of protons in an atom


  atomic number

  
• Number of neutrons in atom

  mass number - atomic number

  
• Number of electrons in an atom

  is the same as the number of protons

  
• Relative atomic mass


  The weighted average mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.