IONIC COMPOUNDS

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Chapter 8

• IONIC COMPOUNDS

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Section 8.1Forming Chemical Bonds

• The force that holds two atoms together is called
  a chemical bond.
• Negative electrons are involved in the formation
  of bonds.
• Review
• electron dot structures
• ionization energy
• stable atoms

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Electron dot structures

• Ar 4s2 3d10 4p4
• of valence electrons?
• Group ?
• We need to know this to draw e- dot.

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Ionization energy

• What is IE?
• Across a period?
• Down a group?

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Stable atoms

• What are the most stable elements?
• What makes them stable?
• How can other atoms become stable?

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Section 8.1Forming Chemical Bonds

• Positive ions form when an atom loses an
  electron. This is called a cation.
• Remember?

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• Reactivity is based on how easily metals lose a
  valence electron.
• The two most active groups of metals are the
  Group 1A 2A elements.
• Transition metals can also lose d sublevel
  electrons.
• In general, metals lose 1, 2, sometimes 3
  electrons.

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Section 8.1Forming Chemical Bonds

• Negative ions form when a nonmetal gains an
  electron. This is called an anion.
• The negative ion of chlorine is chloride.
  Nitrogen is nitride. Fluorine is fluoride.
• In general, nonmetals usually gain 1, 2, or 3
  electrons.

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Example

• What ion is formed from the following atoms?
• Chlorine
• Cl-1
• Nitrogen
• N-3
• Barium
• Ba2

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Practice

• Work practice problems 1-8

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• 1. How do the 2 images of iron nails differ in
  appearance in their properties?
• 2. What chemical reaction do you think caused the
  appearance of the nails on the right?

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Section 8.2The Formation Nature of Ionic Bonds

• During the formation of an ionic bond, valence
  electrons are transferred from one atom to
  another, resulting in the ions.
• Binary compounds contain only 2 different
  elements.
• Na Cl ? Na1 Cl-1

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• Example8-1
• Unprotected aluminum metal reacts with oxygen in
  air, forming a white coating you can observe on
  aluminum objects such as lawn furniture. Explain
  the formation of an ionic compound from the
  elements aluminum oxygen.
• (check by calculating the overall charge)

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• Try practice problem 1 2
• Want to know a shorter way?
• Work 3-6, then 7-9

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Bell Ringer

• 1. How does an ionic bond form?
• 2. Why is CaSO4 not a binary compound?

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Section 8.2The Formation Nature of Ionic Bonds

• A crystal is regular repeating pattern that
  balances the forces of attraction repulsion of
  ions during the formation of an ionic compound.
• A salt (NaCl) crystal is shaped like a cube.
• Melting point, boiling point, hardness are
  physical properties that depend on how strong the
  attraction between ions.

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Section 8.2The Formation Nature of Ionic Bonds

• An electrolyte is an ionic compound whose aqueous
  solution conducts an electric current.

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• Remember that during any chemical reaction,
  energy is either absorbed or released. If energy
  is absorbed, it is known as an endothermic
  reaction. If energy is released, it is known as
  an exothermic reaction. The formation of ionic
  bonds is always exothermic.

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• The formation of ionic bonds is always neutral.
• Stop

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Section 8.3Names Formulas for Ionic Compounds

• The simplest ratio of ions in a compound is
  called a formula unit.
• ie. KBr is a 11 MgCl2 is a 12 ratio
• Three sodium ions for every one phosphide ion is
  Na3P
• The overall charge of a formula unit is zero.
• A monatomic ion is a one-atom ion.
• ie. Formula for the iodide ion is I-1. Calcium
  ion is Ca2. Nitride ion is N-3.

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• An oxidation number or oxidation state is the
  charge of a monatomic ion. The oxidation
  numbers are used to determine the formulas for
  the ionic compounds they form.
• In the chemical formula for any ionic compound,
  the cation is written first. The anion is
  written next. Subscripts represent the number of
  ions of each element in an ionic compound.

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Section 8.3Names Formulas for Ionic Compounds

• Polyatomic ions are ions made up of more than one
  atom. The charge applies to the entire group of
  atoms. It acts as an individual ion. NEVER
  CHANGE SUBSCRIPTS WITHIN ION. Place parentheses
  around the ion if more than one is needed.
• An oxyanion is a polyatomic ion composed of an
  element with oxygen atom(s). Its name comes from
  the element other than oxygen.

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Compounds formed with polyatomic ions

• Example
• A common ionic compound in fertilizers is formed
  from calcium phosphate ions. Write the correct
  formula for this compound.
• Work practice problems

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Section 8.3Names Formulas for Ionic Compounds

• Naming Compounds
• Binary2 elements only
• Name the cation. (element name)
• Name the anion. (root of the element plus ide)
• Example
• 1. KCl
• 2. Magnesium iodide

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• Practice
• 1. AlF3
• 2. Na3N
• 3. Magnesium nitride

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• If the cation has more than one oxidation number,
  use a roman numeral.
• Example
• FeO
• Iron (III) oxide

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• Practice
• 1. Cu2S
• 2. NiCl2
• 3. Cr2O3
• 4. Iron (II) sulfide

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• Ternary Compoundscontains at least one
  polyatomic ion
• Name cation
• Name anion
• Example
• Ba(NO3)2

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• 1. K2SO4
• 2. CaCO3
• 3. Cu(NO3)3 ?transition metal
• 4. Mg3(PO4)2
• 5. Copper (II) carbonate
• 6. Magnesium iodate

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8.4- Metallic Bonds Properties of Metals

• The electron sea model says that all metal atoms
  in a metal is solid contribute their valence
  electrons to form a sea of electrons.
• Delocalized electrons are the e- in the outer
  energy level of metallic atoms because they are
  free to move about, NOT held by a specific atom.

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Pic of mallea,duct, cond
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Properties of metals

1. They have variable melting points.
2. Are malleable- can be hammered into sheets
3. Are ductile- can be drawn into wire
4. Good conductors because the delocalized e- move
   the heat from one place to another very quickly
   easily.

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• Alloy- mixture of elements that have metallic
  properties.
• Example
• Steel- Fe C
• Pewter- Sn, Sb, Pb
• Sterling silver- Ag Cu