Ionic, Covalent and Metallic
Bonding
The type of bond that atoms form
between them affect the
substances properties
Why do atoms form bonds
• Atoms form bonds in order to have a stable
electron configuration.
• You will recall that Noble Gases are the least
reactive (most stable) elements. They have 8
valence electrons making them very stable.
• All atoms try to obtain a stable octet (8
electrons) in their outer energy level by either
gaining electrons, losing electrons or sharing
electrons.
Bonds can Stretch and Bend
• Because bonds are formed from the attraction
between the nucleus of an atom and the
electrons of another atom the bond is not a rigid
structure but rather a flexible spring-like
attraction.
• The electrons are in constant motion causing
the forces of attraction and repulsion to
constantly change, resulting in the distance
between two bonded atoms to constantly
change.
Ionic Bonds
• Formed between ions of opposite charges.
• The nucleus of one ion attracts the
electrons of the other ion.
• Ionic bonds are usually formed by the
transfer of electrons from a metal to a
nonmetal.
• Cations must free up electrons for the
anions to accept.
Ionic Compounds
• Ionic compounds are a network of ions
and not molecules.
• The simplest ratio of ions that combine to
form an ionic compound is called a
formula unit
• The ratio of ions in an ionic compound
depends on the charges of the ions
Characteristics of Ionic Compounds
• Ionic Compounds:
• are always solids at room temperature
• conduct electricity when dissolved in
water or in the molten state
• have high melting and boiling points
• are brittle
• are usually white and crystaline
Metallic Bonds
• Metallic bonds:
• only exist between atoms of two different
metals or atoms of the same metal
element.
• Are formed by delocalized valence
electrons, (electrons that do not belong to
only one nucleus but are free to move
from nucleus to nucleus)
Metallic bonds cont.
• Metals atoms also have an arrangement
called close packed stacking in which
atoms stack in layers with the atoms on
the top layer sitting between atoms on the
lower layer.
Characteristics of metallic bonds
• Properties of Metals:
• Malleable ( can be hammered into a thin
sheet)
• Ductile (can be drawn into a wire)
• Can conduct heat and electricity easily
• Shiny
• All these properties can be attributed to
the delocalized electrons and the close
stacking of atoms
Covalent Bonding
•
•
•
•
Covalent Bonds:
Often form between two nonmetals
Formed by the sharing of electrons
Polar covalent bonds are formed when atoms do
not share electrons equally like in a water
molecule oxygen attracts the electrons more
strongly than hydrogen.
• Nonpolar covalent bonds the atoms share the
electrons equally two identical atoms have
nonpolar covalent bonds
Covalent bonds cont.
• Atoms can share more than one pair of
electrons. These multiple bonds usually
occur between carbon, oxygen, sulfur, or
nitrogen atoms.
• The more bonds two atoms share the
stronger the bond is and the more energy
that is required to break it.
• Longer bonds are weaker than shorter
bonds
Polyatomic ions
• A group of nonmetals that are covalently bonded
with an overall charge.
• Polyatomic ions are found in ionic compounds
• Most polyatomic ions have a negative charge
with the exception of ammonium which is
positively charged NH4+1
• When there is more than one of a polyatomic ion
in a compound it must be place in parentheses
and the subscript put outside of the parentheses
• (NH4)2SO4 is the correct formula for ammonium
sulfate.