Atomic Structure

Atomic Structure

1. Fundamental Particles

   • Protons
     • Relative charge = +1
     • Relative mass= 1
   • Neutrons
     • Relative Charge = 0
     • Relatve mass = 1
   • Electrons
     • Relative mass= negligable
     • Relative charge= -1

2. Mass number and isotopes

   • The mass number ( A) is the number of PROTONS PLUS the number of NEUTRONS
     • It is the BIG number
   • The Atomic number (Z) is the number of PROTONS
     • It is the SMALLER number
   • Isotopes
     • An atom with the same number of protons (and electrons) but DIFFERENT number of neutrons
     • THE SAME CHEMICAL PROPERTIES because they have the same number of ELECTRONS/ the same ELECTRON CONFIGURATION
   • Mass Spectrometry
     • Gives accurate information about 1) the relative abundance of each chemical in the sample 2) relative isotope mass (all the chemicals in the sample)
     • Stages of mass spectrometry
       • 1) IONISATION
         • Using an electron gun
         • knocks one electron off each gaseous atom
       • 2) ACCELERATION
         • Using negatively charged plates
       • 3) DEFLECTION
         • Using an electromagnet
         • The greater the mass over charge value, the lower the deflection
       • 4) DETECTION
         • Using a negatively charged plate
         • Positive ions hit the negatively charged plate
           • producing an electric current
             • The greater the relative abundance, the greater the electric current
     • Carried on SPACE CRAFTS to analyse the ATMOSPHERE, SOIL OF PLANTS, SATALITES and COMETS
     • Samples of the same chemical or rocks taken from different parts of the Earth will have a SLIGHTLY DIFFERENT RATIO OF ISOTOPES

3. Relative atomic mass

   • The average mass of an atom compared to the mass of 1/12th of a carbon-12 atom

4. Relative molecular mass

   • The average mass of a MOLECULE compared to the mass of 1/12th of a carbon-12 atom

5. Relative formula mass

   • Average mass of a formula unit compared to the mass of 1/12th of a carbon 12 atom