4/6/2015. Formed between metals and non-metals Opposite sides of the periodic table CHEMICAL BOND IONIC VS. COVALENT BONDS CHEMICAL BONDING BOND TYPES

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1 CEMICAL BOND CEMICAL BONDING BOND TYPES IONIC VS. COVALENT BONDS Ionic Bond bonding between a metal (cation) & a non metal (anion) that involves the transfer of electrons from cation to anion (forms compounds) Covalent Bonds atoms share electrons (forms molecules) Metallic Bonds Bonding of atoms within metals, involves sharing of free electrons Sea of Electrons Alloys Brass, bronze The attraction between oppositely charged ions Large difference electronegativity Electrons are transferred from one atom to another. IONIC BONDS IONIC BONDING Formed between metals and non-metals Opposite sides of the periodic table [METALS ] + [NON-METALS ] - Lost e - Gained e - 1

2 Energy Energy 4/6/2015 COVALENT BOND BOND FORMED BY TE SARING OF ELECTRONS 0 Bond Length Internuclear Distance CARACTERISTICS OF COVALENT BOND 0 Bond Energy Internuclear Distance Bond Length Distance between 2 bonded atoms at their minimum potential energy (happy or stable state) Bond Energy Energy required to break a bond & form neutral isolated atoms NONPOLAR COVALENT BONDS WEN ELECTRONS ARE SARED EQUALLY 2 or Cl 2 NONPOLAR COVALENT BONDS Equal (same element) or very close in electronegativity (0-0.4 difference) Nonmetal with nonmetal (right side of periodic table not including nobel gasses!) olds all diatomic atoms together ydrogen and Carbon Bonds 2

3 POLAR COVALENT BONDS FIGURE 12.2: PROBABILITY REPRESENTATIONS OF TE ELECTRON SARING IN F. WEN ELECTRONS ARE SARED BUT SARED UNEQUALLY 2 O Copyright by oughton 29 POLAR COVALENT BONDS Unequal electronegativity (always different elements) difference Also between Nonmetals (right side of periodic table not including nobel gasses!) ydrogen often involved ELECTRONEGATIVITY The ability of an atom in a group to attract shared electrons to itself. TABLE 12.1 BOND POLARITY To determine Bond Polarity First determine Bond Type (Covalent or Ionic) Covalent Between 2 non-metals Ionic between a metal and a non metal Then use Electronegativity differences Non Polar Covalent Polar Covalent >2.1 Ionic bond must be made between a metal and non-metal Copyright by oughton 32 3

4 PLACE TESE MOLECULES IN ORDER OF INCREASING BOND POLARITY (OR INCREASING IONIC CARACTER) WIC IS LEAST AND WIC IS MOST? Cl N 2 F CO Copyright by oughton 35 NON-POLAR MOLECULES Sometimes the bonds within a molecule are polar and yet the molecule is non-polar because its shape is symmetrical. POLAR MOLECULES (A.K.A. DIPOLES) Not equal on all sides Polar bond between 2 atoms makes a polar molecule asymmetrical shape of molecule C WATER IS A POLAR MOLECULE CARGE DISTRIBUTION IN TE WATER MOLECULE. O Copyright by oughton 41 4

5 WATER MOLECULE BEAVES AS IF IT AD A POSITIVE AND NEGATIVE END. Copyright by oughton 42 VALENCE ELECTRONS DRAWING LEWIS DOT STRUCTURES Electrons in the outermost energy level of the atom. Group 1 = 1 e - Group 2 = 2 e - Groups = Group # - 10 i.e. Group 13, = 3 e - Symbol represents the nobel gas core of the atom (nucleus and inner e-) dots represent valence e - Always remember atoms are trying to complete their outer shell! The number of electrons the atoms needs is the total number of bonds they can make. Ex.? O? F? N? Cl? C? one two one three one four Drawing molecules (covalent) using Lewis Dot Structures Step 1 count total valence e - involved Step 2 connect the central atom (least electronegative) to the others with single bonds Step 3 complete valence shells of outer atoms Step 4 add any extra e - to central atom Step 5 Fix octets (if possible) IF the central atom has 8 valence e - surrounding it.. YOU RE DONE! 5

6 METANE C 4 This is the finished Lewis dot structure LEWIS DOT NOTATION A bond (2 e-) can be shown as a line (Lone pairs can also be show with a line) Unshared (un-bonded) Pair or Lone pairs Pair of electrons not involved in bonding DOUBLE bond atoms that share two e- pairs (4 e-) O O TRIPLE bond atoms that share three e- pairs (6 e-) N N LEWIS DOT NOTATION What if there are more than one way to draw a diagram? (i.e. where does the double bond go?) TEN YOU AVE RESONANCE (and a resonance structure) Actual structure is a hybrid of all three 6