Physci 2

• Electronegativity


  The tendency for the nucleus of the atoms of elements to attract electrons when they are chemically combined with the atoms of another element
• Electronegativity value


  Describes the ability of an atom's nucleus to compete for electrons with another atom to which it is bonded
• Oxygen has 8 protons in the nucleus whereas nitrogen only has 7
• A bonding pair of electrons will experience more attraction from the oxygen's nucleus that from nitrogen's, thus the electronegativity of oxygen is greater
• Factors Affecting the Electronegativity of an Atom

  • Atomic Size or Radius
  • Effective Nuclear Charge
  • Hybridization State of an Atom
  • Bond Order
  • Oxidation Number
• Atomic Size or Radius


  Electronegativity of a bonded atom decreases as its size or radius increases
• Shielding Effect


  When electrons in the inner electron shells of an atom can shield the outer electrons from the pull of the nucleus
• Effective Nuclear Charge


  Actual amount of positive charge experienced by an electron in a polyelectronic atom
• Hybridization State of an Atom

  Electronegativity increases with increasing s-character of the hybrid orbital
• The s-orbital is nearer to the nucleus thus increasing electronegativity
• Bond Order


  The number of covalent bonds present between to bonded atom
• With the increase in bond order

  The bond distance decreases thus increasing the effective nuclear charge which results to the increase of electronegativity
• Oxidation Number


  Total number of electrons that an atom gains or loses in order to form a chemical bond with another atom
• The electronegativity value


  Increases with the increase in oxidation number
• Types of Chemical Bonds

  • Ionic - Complete transfer of electrons from one atom to another
  • Covalent - Electrons shared between atoms
• Electronegativity Difference


  Determines the type of chemical bond
• Types of Chemical Bond based on Electronegativity Difference

  • Ionic - ∆EN ≥ 1.7
  • Polar Covalent - 1.7 > ∆EN > 0.4
  • Non-Polar Covalent - ∆EN ≤ 0.4
• Octet Rule


  Tendency of atoms to prefer to have eight electrons in the valence shell
• When atoms combine to form compounds, they can give up, accept, or share electrons in order to assemble an octet of electrons in their outer shells
• Covalent Bond


  Formed when atoms share electrons in order to satisfy the octet rule
• Covalent Bond


  • Carbon Atom and Hydrogen Atoms
• Polar Covalent Bond


  Having electronegativity difference greater than 0.4 but not greater than 1.7, producing partial charges and dipole moment
• Polar Covalent Bond


  • H2O (Water)
• Non-Polar Covalent Bond


  Having electronegativity difference less than or equal 0.4, no partial charges and dipole moment, equal sharing of electrons
• Non-Polar Covalent Bond


  • CO2 (Carbon Dioxide)