Chemical Bonding

1
Chemical Bonding

• Chapter 6

2
Chemical Bond

• A marriage between atoms
• a force that holds together the atoms in a
  compound
• BOOK DEFINITION
• A mutual electrical attraction between nuclei and
  valence electrons of different atoms that binds
  the atoms together

3
Bonds

• Forces that hold groups of atoms
• together and make them function
• as a unit.

• Ionic bonds transfer of electrons
• Covalent bonds sharing of electrons

4
Two types of Chemical Bonding

• Ionic Bonding chemical bonding that results
  from the electrical attraction between large
  numbers of cations and anions.
• Generally between a metal non-metal
• Covalent Bonding chemical bonding that results
  from the sharing of electron pairs between two
  atoms
• Generally between two non-metals

5
Determining Bond Type

• Bonding between atoms of different elements is
  never purely ionic and is rarely purely covalent.
  
• to determine the bond type you look at the
  electronegativity of the two elements

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Electronegativity
The ability of an atom in a molecule to attract
shared electrons to itself.
Linus Pauling 1901 - 1994
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Determining Bond Type

• Electronegativity difference of 1.8 or more
• it has an ionic character greater than 50 and is
  classified as Ionic Bonding
• Electronegativity difference of 1.7 or less
• it has an ionic character of 50 or less and is
  classified as covalent bonding

8
Determining Bond Type

• Electronegativity difference of 0.3 to 1.7
• it has 5 - 50 ionic character and is classified
  as a polar-covalent bond
• Polar-Covalent bond a covalent bond in which the
  bonded atoms have an unequal attraction for the
  shared electrons

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Determining Bond Type

• Electronegativity difference of 0.3 or less
• it has an ionic character of 5 or less and is
  classified as a nonpolar-covalent bond
• Nonpolar-Convalent bond a covalent bond in which
  the bonding electrons are shared equally by the
  bonded atoms, resulting in a balanced
  distribution of electrical charge

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COVALENT BONDS
IONIC BONDS
Non Polar
POLAR
0
0.3
1.7
Increasing Sharing of Electrons
Increasing Ionic Character
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Covalent Bonds
Polar-Covalent bonds

• Electrons are unequally shared
• Electronegativity difference between .3 and 1.7

Nonpolar-Covalent bonds

• Electrons are equally shared
• Electronegativity difference of 0 to 0.3

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Polarity
A molecule, such as HF, that has a center of
positive charge and a center of negative charge
is said to be polar, or to have a dipole moment.
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Why Bond?

• Atoms have a natural tendency to become stable.
• - in order to do this they form compounds
• Compounds substance made from two or more
  elements which has properties unlike those of the
  elements.

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Types of Compounds

• Molecular compound compounds that are composed
  of molecules
• Molecule a neutral group of atoms that are held
  together by covalent
• many exist as gases or liquids at room temp.
• Ex Water, Carbon Dioxide

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Types of Compounds

• Ionic compound positive and negative ions that
  are combined so that the numbers of positive and
  negative charges are equal
• Exist as crystalline solids
• DO NOT exist as independent structures, just
  large numbers of () (-) ions.
• Ex Sodium Chloride (table salt)

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Chemical Formulas

• Chemical Formula indicates the relative numbers
  of atoms of each kind in a chemical compound by
  using atomic symbols and numerical subscripts.
• Types of Formulas
• Molecular Formula shows the types and numbers
  of atoms combined in a single molecule of a
  molecular compound
• Formulas Unit the simplest collection of atoms
  from which an ionic compounds formula can be
  established

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Characteristics of Covalent Bonds

• Bond Length the distance between two bonded
  atoms at their minimum potential energy, that is,
  the average distance between the tow bonded
  atoms.
• Bond Energy the energy required to break a
  chemical bond and form neutral isolated atoms.

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Types of Covalent Bonds

• Single Bond a covalent bond produced by the
  sharing of one pair of electrons between two
  atoms
• Double Bond a covalent bond produced by sharing
  of two pairs of electrons between two atoms.
• Triple Bond a covalent bond produced by the
  sharing of three pairs of electrons between two
  atoms.

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Characteristics of Ionic Bonds

• Crystal Lattice orderly arrangement ions form
  to minimize their potential energy
• Lattice Energy energy released when one mole of
  an ionic crystalline compound is formed from
  gaseous ions.

20
Electron Dot Diagrams

• What are they?
• a very simple way of showing an elements valence
  electron configuration
• An electron configuration notation in which only
  the valence electrons of an atom of a particular
  element shown, indicated by DOTS placed around
  the elements symbol

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How to Write Dot Diagrams

• Write the elements symbol
• Place dots around the symbol just like they fill
  orbitals
• 4 sides 4 orbitals
• Two dots per side two electrons per orbital

22
Lewis Structures

• Lewis Structures formulas in which atomic
  symbols represent nuclei and inner-shell
  electrons, dot-pairs or dashes between two atomic
  symbols represent electron pairs in covalent
  bonds, and dots adjacent to only one atomic
  symbol represent unshared electrons
• unshared pair (or lone pair) a pair of
  electrons that is not involved in bonding and
  that belongs exclusively to one atom.

23
Structural Formula

• Structural Formula indicates the kind, number,
  arrangement, and bonds but not the unshared pairs
  of the atoms in a molecule

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Molecular Geometry

• the polarity of each bond, along with the
  geometry of the molecule, determines molecular
  polarity
• Molecular Polarity the uneven distribution of
  molecular charge

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VSEPR Theory

• Valence-Shell, Electron-Pair, Repulsion
• STATES the repulsion between the sets of
  valence-level electrons surrounding an atom
  causes these sets to be oriented as far apart as
  possible

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VSEPR Theory

• Each bonded sets wants and gets its own space
• Unshared or Lone electron pairs are also included
• - they want and get their own space

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Orbital Hybrids

• Hybridization the mixing of two or more atomic
  orbitals of similar energies on the same atom to
  produce new orbitals of equal energies.
• Ex Carbon 1s?? 2s?? 2p? ?
• - this will hybridize into
• Carbon 1s?? 2s? 2p? ? ?
• - called an sp3 hybrid