Electronegativity

• what is electronegativity?


  the ability of an tom to attract the bonding electron in a covalent bond
• factors that effect the level of attraction between the nucleus and the bonding electrons.


  1. the nuclear charge - the number of protons in the nucleus
  2. the atomic radius - the physical distance between protons and the bonding electrons
  3. the amount of shielding from inter electron shells
• pauling scale 


  a scale used to measure electronegativity
• why are noble gases not assigned electronegativity values 


  they do not need to attract electrons since they have full outer shells
• what is the general trend in electronegativity across a period

  • electronegativity increases due to the addition of a proton as you go from left to right
• what is the general trend in nuclear charge across a period

  the nuclear charge increases because there is a greater number of protons in the nucleus
• what is the general trend in shielding across a period 



  the shielding stays the same since the outer shell stays the same across a period.
• what is the general trend in atomic radius across a period 



  the atomic radius decreases since the nuclear attraction on the bonded atoms increases
• general trend up a group 


  • electronegativity decreases because the atomic radius increases since there are more electrons in the atom. this therefore increases the shielding.
  • these factors outweigh the proton increase therefore the electronegativity decreases
• What are the four most electronegative atoms in order?

  Fluorine, Oxygen, Nitrogen, Chlorine
• How can you predict bond types?

  • the bonds between atoms of different elements are rarely purely ionic or purely covalent.
  • these is a gradual transition from ionic to covalent bonding.
  • electronegativity difference can predict the type of bonds between atoms.
• if the difference in electronegativity is around 4.0 or less what is the bond?


  Non-polar covalent
• If the difference in electronegativity is around 4.0 - 2.0 what is the bond?


  polar covalent
• If the difference in electronegativity is above 2.0 what is the bond?


  ionic