Chapter 6 – Chemical Bonds
6.1 Ionic Bonding
• When the highest occupied energy level of
an atom is filled with electrons, the atom is
stable and not likely to react.
• Electron dot diagram – symbol represents
the nucleus and each dot represents a
valence electron (also called Lewis Dot
Diagram or Lewis Dot Structure)
Ionic Bonds
• Elements achieve stable e- config. through
the transfer of e• Form between a metal and a nonmetal
• Metal gives up e-; nonmetal gains e• Ions (atoms with charges) are formed
• Metal becomes + ion, nonmetal becomes
a neg. ion
• Opposite charges attract each other
Sodium Chloride
• Chemical bond – the force that holds
atoms or ions together
• Cation – positive ion
• Anion – negative ion
• Ionic bond – the force that holds ions
together
• Ionization energy – the amount of energy
used to remove an e• Lower ionization energy = easier to remove an
electron
Ionic Compounds
• Chemical Formula – shows which
elements are in a compound and the ratio
– Ex. NaCl, MgCl2
• Crystal lattices – ions are arranged in an
orderly, 3-D structure
• Crystals – solids whose particles are
arranged in a lattice structure
• Properties of ionic compounds
– High melting points
– Poor conductors in solid form
– Good conductors when melted
– Brittle (shatter when struck by a hammer)
When an ionic crystal is struck,
ions are moved from their fixed
positions. Ions with the same
charge repel one another and
the crystal shatters.
6.2 Covalent Bonds
• Form when two or more atoms SHARE e• Form between two or more nonmetals
• Can be polar or nonpolar
– Polar – e- are NOT shared equally
– Nonpolar – e- ARE shared equally
• Form molecules (neutral group of atoms
that are joined by covalent bonds)
• Atoms may share 1, 2, or 3 prs. of e-
Many nonmetals exist as
diatomic molecules.
Diatomic means “two
atoms”
Polar Covalent Bonds
• One atom has a greater attraction for the
e-, making one end of the molecule have a
partial neg. charge. The other end has a
partial pos. charge.
Water is a polar molecule.
The e- spend most of their
time with the Oxygen
atom, making the O end
of the molecule slightly
negative and the H end
slightly positive.
Nonpolar Covalent Bond
Both atoms have an equal attraction for the
electrons, so they share them equally.
Attraction Between Molecules
• Attractions between polar molecules are
stronger than between nonpolar
molecules.
6.3 Naming Compounds and
Writing Formulas
• Binary Ionic Compounds
– 1st word – name of metal
– 2nd word – name of nonmetal ending in –ide
– If the metal is a transition metal, a roman
numeral is placed between the metal and
nonmetal to indicate which ion.
• Ex. Sodium Chloride, Copper (II) Chloride
Polyatomic Ions
• Covalently bonded group of atoms with a
charge.
• Polyatomic ions act like single atoms when
forming chemical bonds.
• Polyatomic ions are COVALENTLY
bonded to each other, but as a group they
bond IONICALLY to another ion.
Writing Formulas for Ionic
Compounds
• Symbol of cation is written first, followed
by the symbol of the anion
• Use subscripts to show the ratio of ions
• Parentheses are used to enclose
polyatomic ions
Naming Molecular Compounds
• MOST metallic element appears first in the
name (the one closer to the left on the
periodic table)
• If both elements are in the same group,
the one closer to the bottom is listed first
• Use prefixes to indicate the number of
atoms
• The prefix “mono-” is not used in the first
element name.
Writing Molecular Formulas
• Write the symbols for the elements in the
order that they appear in the name
• Use the prefixes to determine the number
of atoms
• Use subscripts to show how many atoms
of each element are in a molecule
6.4 The Structure of Metals
• Metallic Bonds
– Form between two or more metal atoms
– Attraction between the metal cation and the
shared electrons that surround it
– “sea of electrons”
• Metals are malleable and are good
conductors because of metallic bonds.
• Alloys
– Mixture of two or more elements at least one
of which is a metal
– Can be designed with specific properties by
varying the types and amounts of elements in
them.
Bronze is a common alloy made usually of
copper and tin.
Steel is an alloy of iron that contains small
quantities of iron.