Binary ionic compounds - Bishop Moore High School

Chapter 7
Ionic Compounds and Metals
Section 7.1
Ion formation
Chemical Bonds
A chemical bond is the force that holds two
atoms together.
• Can form by the attraction between the
positive nucleus of one atom and the
negative electrons of another
• Can form between positive and negative ions
Valence Electrons
• Electrons in the outermost principal energy level
• Shown in the electron dot structures
• Octet rule – atoms will gain, lose or share
electrons to obtain 8 valence electrons
• The valence electrons determine the bonding
properties of the atom
Positive Ion Formation
• A positively charged ion is called a cation.
• Positive ions are formed when an atom loses
one or more valence electrons
• Metals make positive ions
Negative Ion Formation
• A negatively charged ion is called an anion.
• Negative ions are formed when an atom gains
one or more electrons in its valence shell.
• Nonmetals make negative ions.
7.2: Ionic bonds and ionic compounds
Formation of an Ionic Bond
• An ionic bond is the electrostatic force that holds
oppositely charged particles together in an ionic
• Compounds that contain ionic bonds are called
ionic compounds.
• Ionic compounds are formed between
metals (+ charge) and nonmetals (- charge).
Binary Ionic Compounds
• Contain a metallic cation and a nonmetallic
• Formation of Binary Ionic Compounds
– Electron(s) is/are transferred from metal to
– Metal becomes positive, nonmetal becomes
– Opposite charges attract
Properties of Ionic Compounds
• Take the structure of a crystal lattice
– Many units of positive and negative ions stick together
in a three-dimensional geometric arrangement
• Can conduct electricity when dissolved in water
(they are electrolytes and break into ions when
dissolved in water), but not in solid form
• Melting point, boiling point and hardness depend
upon how strongly the ions are attracted to each
Formulas for Ionic Compounds
• Monatomic ions are one-atom ions
– Examples: Mg2+ , Br-1
• Oxidation numbers are the charges on ions
– Note: some elements have multiple oxidation
states – you will have a periodic table to tell this
• Binary ionic compounds are made of two
monatomic ions (one positive, one negative)
Formulas for Binary Ionic
• Symbol for cation is written first, anion second
• Subscripts tell the number of atoms of each
• What are the following compounds made of?
– CaF2
– Na2S
– NaCl
1 calcium, 2 fluorine
2 sodium, 1 sulfur
1 sodium, 1 chlorine
Naming Binary Ionic Compounds
• Name the cation first
• Name the anion second with –ide at the end
• Examples
– CaF2  calcium fluoride
– Na2S  sodium sulfide
– NaCl  sodium chloride
Try Naming a few more
Binary Ionic Compounds
• K2O
potassium oxide
• Al2S3
aluminum sulfide
• Na3N
sodium nitride
What if the cation has more than
one oxidation state?
• You tell which ion was used by putting a Roman Numeral after
the name of the cation
• Example:
– CuS
• We know S was -2 (that’s the only one it makes)
• If there is only one atom of each element, the Cu must
have been +2
• So, the name is written as Copper (II) sulfide [the “II”
indicates the charge]
• Make sure, especially with transition elements, that you are
checking the oxidation states
Writing Formulas for Binary
Ionic Compounds
• Look up the charges for each element
• For a compound to form, the total charge
must balance out to zero (positive charges
must equal negative charges)
• Example:
– Sodium bromide
• Na is +1, Br is -1
• Only need one of each to balance
• Formula is NaBr
Try writing some more formulas
Binary Ionic Compounds
• Potassium Iodide
• Aluminum bromide
• Magnesium chloride
• Cesium nitride
Formulas for Polyatomic
Ionic Compounds
• Polyatomic ions are ions that are made up of
more than one atom
• You will have a chart for these and do not
have to memorize them.
• Examples:
– SO42- = sulfate
– CN- = cyanide
– NH4+ = ammonium
Naming Polyatomic
Ionic Compounds
• Name the cation first, anion second
• Name the polyatomic as is – don’t change its
name at all
• Examples:
– Ca3(PO4)2
– Mg(CN)2
– NH4Cl
calcium phosphate
magnesium cyanide
ammonium chloride
Now you try naming
Polyatomic Ionic Compounds
• NaNO3
sodium nitrate
• Ca(ClO3)2
calcium chlorate
• Al2(CO3)3
aluminum carbonate
Writing formulas for
Polyatomic Ionic Compounds
• Same as binary ionic compounds EXCEPT you
may not change anything in the polyatomic
ion formula
• Put them in a (parenthesis) and put subscripts
outside that parenthesis
• Example:
– Calcium Nitrate
• Ions are Ca2+ and NO3• Formula will be Ca(NO3)2
Now you try writing formulas for
Polyatomic Ionic Compounds
• Sodium hydroxide
• Copper (II) nitrate
• Silver chromate
7.3: Metallic bonds and the
properties of metals
• The electron sea model proposes that all the
metal atoms in a metallic solid contribute
their valence electrons to form a “sea” of
• Since the electrons are free to move, they are
called delocalized electrons
• A metallic bond is the attraction of a metallic
cation for delocalized electrons
Properties of Metals
Moderately high melting points
High boiling points
Malleable, ductile, durable
Conduct heat and electricity well
Transition metals are harder/stronger than
alkali metals because the transition metals
have more delocalized electrons

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