Ionic Bonds
Building Science Champions
Objectives
• Explain the differences between
an atom and an ion.
• Describe how an ionic bond
forms.
• Identify the properties of ionic
compounds.
Key terms
• Ion
• Ionic bonds
• Polyatomic ion
• Crystal
Electron Transfer
• In order for elements to bond with one
another they must have an open place for
a valence electron.
• Atoms that have 4 or fewer valence
electrons are said to lose electrons.
• Atoms that have 5 or more valence
electrons are said to gain electrons.
Ion
• An ion is an atom or group of atoms that have
become electrically charged.
• Atoms become electrically charged by gaining
or losing an electron.
• When an atom loses an electron it loses a
negative charge and becomes positive.
• When an atom gains an electron, it gains a
negative charge and becomes negative.
Ions and their
charges
Name
Charge
Symbol
Name
Charge
Symbol
Lithium
1+
Li+
Iodide
1-
I-
Sodium
1+
Na+
Bicarbonate
1-
HCO3-
Potassium
1+
K+
Nitrate
1-
NO3-
Ammonium
1+
NH4+
Oxide
2-
O2-
Calcium
2+
Ca2+
Sulfide
2-
S2-
Magnesium
2+
Mg2+
Carbonate
2-
CO32-
Aluminum
3+
Al3+
Sulfate
2-
SO42-
Fluoride
1-
F-
Phosphate
3-
PO43-
Chloride
1-
Cl-
A plus charge represent elements/compounds that
have lost an electron, a negative charge represents
elements/compounds that have gained an electron.
A subscript
represents the
number of that
element only.
Bonds,
Ionic bonds!
• An ionic bond is the attraction between two oppositely
charged ions. (Usually between metals and nonmetals)
• When the two ions come together, the opposite charges
cancel each other out.
• Locate Sodium on your ion chart. What is its charge?
• Locate Chloride on your ion chart. What is its charge?
Na + Cl
Na+ Cl-
Ionic Bonds
• Compounds are electrically neutral.
• Ions come together to balance out each others charge.
• The NaCl example is a 1:1 ratio, meaning there is 1
Sodium ion and 1 Chlorine ion.
• How many chloride ions would be needed to cancel
out magnesium?
2 chloride ions
Ionic Bonds
• Reaction between metals and nonmetals often result in
IONIC COMPOUNDS.
• These reactions easily occur between the metals in
Group 1 and halogens in Group 17.
• Why do you think these two families easily bond?
Their number of valence electrons. Trying to get 8
valence electrons and by adding them together the
magic number of 8 is achieved.
Ionic Questions?
• How could an atom of sodium become more stable?
Lose an electron
• How could chlorine become more stable?
Gain an electron
• What happens when sodium and chlorine bond?
They neutralize each other
Polyatomic Ions
• Polyatomic ions are made of more than one atom.
• Polyatomic ions are a group of atoms that work as one.
• They have a positive or negative charge.
• If a polyatomic ion combines with an ion of an
opposite charge an ionic compound is formed.
• Examples: CO32- = carbonate ion
Ca2+ = calcium ion
CaCO3 = calcium carbonate
Naming ion
compounds
• The name of the positive ion comes first, followed by
the name of the negative ion.
• The positive ion is usually a metal.
• If a negative ion is in the compound, the end of its
name changes to - ide MgO (magnesium oxide)
• If the negative ion is polyatomic, its name is
unchanged. Na2CO3 (sodium carbonate)
Properties of Ionic
Compounds
• Properties of ionic compounds include:
• Crystal shape
• High melting point
• Electrical conductivity
Crystal Shape
• Ions form an orderly, three-dimensional arrangement
called a crystal.
• In ionic compounds, every ion is attracted to ions near
it that have an opposite charge
• Positive ions near negative ions and negative ions near
positive ions.
High melting points
• Ions are held together in a crystal by attractions
between oppositely charged particles.
• Ions separate when the particles have enough energy to
break apart.
• It takes temperature of 801OC
Electrical
conductivity
• When ionic compounds are placed in water, the
solution conducts electricity.
• Electricity is the flow of electric charge and ions have
electric charge.
• A solid ionic compound does not mix electricity well.
• Melting ionic compounds also allows them to conduct
electricity.
Review
• An ion is an atom or group of atoms that have become
electrically charged.
• Ions are either positive or negative.
• An ionic bond is the attraction between 2 oppositely
charged ions.
• Compounds are electrically neutral.
• When atoms have 4 or fewer electrons, they will LOSE
electrons and atoms with 5 or greater electrons will GAIN
electrons. This process takes place during bonding.
References
• Anderson, M. et all (2012) Physical Science. McGrawHill: Columbus
• Frank, D.V et al (2001). Physical Science. Prentice
Hall: New Jersey