Ionic Compounds:

1
Ionic Compounds

• Compounds that are made of oppositely charged
  ions.

2
Forming Ionic Compounds

• Elements can combine to make ionic compounds when
  their atoms lose or gain electrons.
• Any atom that has gained or lost electron(s) is
  called an ion and is now charged.
• When atoms gain an electron, they are more
  negative (electrons are negatively charged
  particles) and are called anions.
• When atoms lose an electron, they are more
  positive and are called cations.
• Ionic compounds are when an anion and a cation
  come together to form a neutral compound, which
  is more stable.

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• The loss and gain of electrons is what makes a
  full outer energy level.
• Remember, we only need to look at the outer
  energy level. These electrons are called valence
  electrons.
• Ionic compounds are usually composed of one metal
  (left side of periodic table) and one non-metal
  (right side).
• E.g. How many valence electrons does Lithium
  have? Do you think it will gain or lose its
  electron(s)? Why?
• Answer
• It has 1 valence electron. It will lose its
  electron when forming an ion because it is easier
  to lose one than gain 7 in order to have its
  last energy level filled up.

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Naming Binary Ionic Compounds

• There are two ways to identify a compound
• By its chemical name
• By its chemical formula
• These are the IUPAC rules for naming
• 1. The 1st part always identifies the positive
  ion (metal cation)?
• 2. The 2nd part always identifies the negative
  ion (non-metal anion)?

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Examples

• Magnesium and phosphorus make magnesium
  phosphide.
• Sodium and chlorine make
• Sodium chloride
• Calcium and bromine make
• Calcium bromide

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Examples

• Write the names of the following binary ionic
  compounds
• MgBr2 CaI2 Al2O3 KCl
• Magnesium bromide
• calcium iodide,
• aluminum oxide,
• potassium chloride.

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Activity 4-2

• Text p. 143.
• Use hole punches as valence electrons
• Step 1 Find metal on periodic table and write
  the symbol.
• Step 2 Figure out how many valence electrons it
  has (hint look at the column number it is in)?
• Step 3 record the number of valence electrons
• Step 4 Find non metal and write the symbol
• Step 5 Figure out how many valence electrons it
  has
• Step 6 record the number of valence electrons
• Step 7 Give the metals electrons to the
  non-metal
• Step 8 You may have to add extra metals or
  non-metals in order to fill the valence shell.

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Writing the Chemical Formula

• You wont always be able to use cut outs, so
  follow these steps for a faster way of
  determining the chemical formula
• Step 1 identify each ion and its charge
• Step 2 Determine the total positive charge and
  total negative charge needed to equal zero.
• Step 3 Note the ratio of cations to anions
• Step 4 Use subscripts to show the ratio of ions.

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Examples

• Aluminum Fluoride
• 1. Aluminum Al3 Fluoride F-
• 2. Al3 3 F- (-1) x 3 3-
• 3. 1 Al3 3 F-
• 4. AlF3

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Examples

• Try magnesium Nitride
• Try page 146 6-8

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Multivalent Metals

• Some metals have more than one ion charge listed
  in the periodic table. These elements are called
  multivalent metals
• Eg. Copper can be a 1 or 2 charge.
• To distinguish between the two, we use Roman
  Numerals after the element name.
• Eg. Cu1 is written Copper(I) and Cu2 is
  written Copper(II)

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Chemical Formula for Multivalent Metals

• Example SnS2
• Step 1 Identify the metal
• Sn (tin)?
• Step 2 Verify that the metal can form more than
  one kind of ion
• Sn2 and Sn4
• Step 3 Determine the ratio of ions in the chem
  formula
• 1 tin 2 sulfide
• Step 4 Note the charge of the anion
• 2-

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• Step 5 The positive and negative charges must
  balance out so the net charge is zero.
• Total neg. charge 4-
• Total pos. charge 4
• Step 6 Determine what charge the metal ion must
  have to balance the anion.
• 1 Sn? 4
• Step 7 Write the name of the metal ion
• The name of the metal ion is tin(IV)?
• Step 8 Write the name of the compound
• Tin (IV) sulfide

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Examples

• Cu3N
• Answer
• Copper (I) nitride

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Polyatomic Ions

• A polyatomic ion is an ion made up of more than
  one atom
• Poly many
• These ions usually end in -ate.
• Examples Ammonium NH4
• Phosphate PO43-
• Carbonate CO32-
• Sulfate SO42-
• Hydroxide OH-
• Nitrate NO3-

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Chemical Formula with Polyatomic Ions

• Example Aluminum carbonate
• Step 1 Use the periodic table and a talbe of
  common polyatomic ions to identify each ion and
  its charge
• Aluminum Al3
• Carbonate CO32-
• Step 2 Determine the total positive charge and
  total negative charge to equal zero.
• Al3 2 (3) 6
• CO32- 3(2-) 6-
• (6) (6-) 0

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• Step 3 Note the ratios of cations to anions
• 23
• Step 4 Use the subscripts to show the ratio of
  ions. Place the polyatomic ion in brackets if it
  needs a subscript.
• Al2(CO3)3
• Now, you try Ammonium sulfate
• Answer
• (NH4)2 SO4
• Now work on questions on page 150 9 and 10
• Page 151 1-8

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Molecular Compounds

• It is a compound formed when atoms of 2 or more
  different elements share electrons.
• They are similar to ionic compounds, but instead
  of one element giving its electrons to the
  other, they share the electrons between the two
  atoms.
• The shared electrons form a covalent bond.
• Molecules can be formed by two or more of the
  same element OR two or more of different
  elements.
• E.g. Oxygen found in the atmosphere is O2
• Oxygen is not a compound, since it contains only
  one type of atom.

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Activity 4-3

• Use p. 154 in your text to follow the directions
  for activity 4-3

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Naming Binary Molecular Compounds

• E.G. carbon dioxide
• Tells us 2 pieces of info
• Compound is composed of carbon and oxygen
• Tells you the ratio of the two elements
• Carbon 1
• Oxygen 2 (di)?
• di is a prefix that tells you the number of
  atoms in that element.

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Using the Prefixes

• Smog has a lot of molecular compounds in it,
  nitrogen dioxide is an example.
• Use the four steps to name binary molecular
  compounds

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• Step 1 Count the of atoms of the first element
  in the chemical formula
• Example N2O4
• of nitrogen 2
• Step 2 Write the appropriate prefix followed by
  the name of the element. (mono- is never used if
  it is the first name in the molecule)?
• Dinitrogen
• Step 3 Count the of atoms in the second
  element
• of Oxygen4
• Step 4 Write the prefix and the element and
  finally the suffix (-ide)?
• Tetroxide
• Final name dinitrogen tetroxide

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You try it!

• BrCl (used to detect mercury in water)?
• Answer
• Bromine monochloride
• Try page 156 1-4

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Writing Chemical Formulas for Binary Molecular
Compounds

• Step 1 Write the chemical symbol of 1st element
• Example phosphorus trichloride
• P
• Step 2 Determine the number of atoms in 1st
  element
• of P 1
• Step 3 Write chem. Symbol of 2nd element
• Cl
• Step 4 Determine of atoms in 2nd element
• of Cl 3
• Write formula
• PCl3

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Try These

• P. 158 3, 6.