Chemical bonds

1

• Chemical bonds
• Attractive force which holds atoms or ions
  together.
• Why do atoms form bonds?
• Noble gases have filled valence shells. This is
  a very stable arrangement from an energy
  standpoint.
• Atoms that have unfilled valence shells can
  become more stable if the right number of
  electrons are added to the level
• Atoms will undergo chemical reactions to form
  bonds so that they can become more stable

2

• I. Contd
• contd
• The octet rule atoms will undergo chemical
  reactions so as to acquire the stable electron
  configuration of a Noble Gas.
• Electron dot diagrams
• II. Ionic Bonding
• Transfer of electrons from the valence shell of
  one atom to the valence shell of another atom
• Ionic bonding results in an ionic compound, which
  is composed of a metal bonded to a nonmetal or a
  metal bonded to a polyatomic ion
• Chemical formulas

3

• Contd
• Ion formation
• Ion size
• Dissolved ions
• Ionic crystals
• Properties of ionic compounds
• Covalent bonding
• The sharing of a pair of electrons between atoms
• Covalent bonding results in a covalent compound,
  which is a nonmetal bonded to another nonmetal or
  a nonmetal bonded to a metalloid

4

• Contd
• The smallest part of a covalent compound is a
  molecule
• Diatomic molecules elemental form in which
  there exists two atoms of the same element bonded
  together
• Multiple covalent bonds
• Unequal sharing of electrons
• Some elements more strongly attract the electrons
  in a bond than others, resulting in the electrons
  spending more time in the valence shell of one
  atom than in another.
• Polar covalent bond covalent bond in which
  electrons are not shared equally
• Polar molecules can result from polar covalent
  bonding. The shape of the molecule also plays a
  role in determining whether or not a molecule
  will be polar
• Polarity of molecules results in a greater
  attraction between molecules than otherwise
  would occur

5

• Naming compounds
• Binary ionic compounds
• Name the metallic element, then the nonmetallic
  element
• Change the ending of the nonmetal to ide
• For metallic elements with multiple ions, use a
  roman numeral to indicate which ion is present
• Ternary ionic compounds
• Composed of three or more elements (compound
  usually contains a polyatomic ion)
• Name the positive half and then the negative half
• Do not use prefixes
• Do not change the ending of the polyatomic ions
  name

6

• Contd
• Binary covalent compounds
• Name the elements in the order in which they
  appear
• Use a prefix in front of the first elements name
  only if there are two or more atoms
• The second elements name is always preceded by a
  prefix and change the ending of the second
  elements name to -ide
• The prefixes indicate the number of atoms of the
  element present
• Prefixes
• mono- 1 di- 2
• tri- 3 tetra- 4
• penta- 5 hexa- 6
• hepta- 7 octa- 8
• nona- 9 deca- 10

7

• Contd
• contd
• If the prefix ends in an a or an o and the
  element name begins with an a or an o, drop the
  last letter of the prefix
• Formula writing
• Metallic bonding
• Attraction between a metal cation and the
  electrons surrounding it
• The more valence electrons that metal atom can
  contribute to the shared pool of electrons, the
  stronger the metal is
• The mobility of the shared electrons within the
  crystal lattice explains the electrical
  conductivity and malleability of metals

8

• Alloys
• A mixture of two or more elements, one of which
  is a metal
• They have properties of metals
• The properties of alloys can be changed by
  varying the types and amounts of the elements
  used to make it
• Examples
• Bronze copper and tin
• Brass copper and zinc
• Steel iron and carbon
• Stainless steel iron and chromium and almost no
  carbon