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CHEMICALBONDING
THE FORMATION OF IONIC
COMPOUNDS
• Conductivity: physical property of metals, ability of electrons to move
freely throughout a material
• Few compounds are able to conduct electricity in the solid state
• BUT some conduct electricity when dissolved in water
• These compounds are called electrolytes
• Example: Sodium chloride (table salt); potassium iodide; calcium
oxide
• Non-electrolytes do not conduct electricity in water
• Example: carbon dioxide, methane, silicon dioxide
WHY?
• The other name for electrolytes is IONIC COMPOUND
• Ionic compounds consist:
METAL + NON-METAL = IONIC COMPOUND
Atoms can gain or lose electrons in their outer layer to become more
stable
They want to have a similar outer shell to their nearest noble gas
EXAMPLE
• Draw the Bohr Diagram for the following elements:
• Sodium
• Fluorine
• Neon
MAKING IONS
• Atoms follow the octet rule: each main group element wants to have eight
electrons in its outer shell
• Atoms gain or lose electrons to get to 8 in the outer shell
• Ion: atom (or group of atoms) that has gained or lost one or more electrons
• Anion: an atom that carries a negative charge because it has more electrons
than protons
• Cation: an atom that carries a positive charge because it has more protons
than electrons
• Valence electrons: electrons that are found in the outer shell
(level) of the atom
• Metals tend to lose electrons and become cations
• Non-metals (except noble gases) tend to gain electrons and
become anions
EXAMPLES
• Draw the ions for:
• Sodium (Na1+)
• Fluorine (F1-)
• Neon (Ne)
IONIC BONDING
• Occurs with a metal and non-metal
• Example: Sodium Chloride
COVALENT BONDING
PRACTICE
• LiF
• SrO
• Na2O
MOST OF THE CHEMICALS WE
ENCOUNTER ARE MOLECULAR
COMPOUNDS, INCLUDING:
sugar
water
Acetylsalicylic
acid, or Aspirin
SOFT DRINKS
Sugar
C12H22O11
Water
H2O
Carbon
Dioxide
CO2
LIVING ORGANISMS
• Make thousands of different
kinds of molecular
compounds
• Sugars, fats, and proteins
are all molecular
compounds
• Some of them are very
large, containing thousands
of atoms in a single
molecule
compounds
Ionic
Covalent
- metal and nonmetal
- two non-metals
- transfer of electrons
- sharing of electrons
- cations and anions
- more electronegative
goes first
- form formula units
- form molecules
MOLECULAR COMPOUNDS
• The majority of all known compounds are molecular
• Molecules consist of two or more non-metal atoms joined by a
covalent bond
• A COVALENT
BOND forms when atoms share electrons
• The chemical formula gives the exact numbers of atoms in each
molecule
• Diatomic molecules consist of only two atoms of either the same
or different elements
• when two NONMETALS come in contact they will share electrons
rather than transferring them, ex. O and O
covalent bond
• forms as a result of sharing of electrons
• very strong, stronger than ionic bond
• atoms that are covalently bonded form molecules
• when two atoms form a covalent bond the sharing of electrons
allows each to satisfy the octet rule
Lewis Structures of Molecules
• shared electrons are shows as a dash
• pairs of valence electrons surrounding each atom
and not involved in bonding are called lone pairs
Ex. O2
ex. I2, N2, CO2, H20
IONIC BOND VS COVALENT BOND
An Ionic bond is
the simultaneous
strong attraction
of positive ions
and negative ions
A covalent bond
results from the
sharing of outer
electrons between
non-metal atoms