Ionization versus Dissociation

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Ionization versus Dissociation
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Ionization

• To remove a negative charge from a positive
  charge.
• The process of separating electrons from protons
  is called ionization.

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Dissociation

• Some very similar to ionization that happens to
  solids. When the ions in a crystal lattice are
  separated, the process is called dissociation.
• Example sodium chloride in water.
• Dissociation occurs because of solvation, which
  requires interaction of similarly electrical
  properties.

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Differences between Ionization and dissociation

• Ionization, the force comes from within the atom.
• Dissociation, the force comes from outside the
  atom and is the interaction between two or more
  compounds.

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Ionic Compounds

• Ionization takes place to form solid ionic
  crystals.
• Example Sodium Chloride (Table salt)
• Positive sodium ions and negative chloride ions
• Ionic crystals can then interact with water
  molecules to dissociate.
• Resulting in a solution that conducts
  electricity.

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Microscopic Representation of Ionization

• Energy must be added to the neutral atom to
  remove an electron from a proton.
• The amount of energy depends on the type of atom.

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Ionization is unique to the type of atom

• Each element has a characteristic ionization
  energy.
• Example Chlorine is 2.5 times greater than that
  for sodium.

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Importance in Understanding Ionization and
Dissociation

• Together these factors help explain important
  macroscopic properties.
• Solubility
• Hardness
• Conductivity

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Electronegativity

• Covalent Bonds Bonding between atoms of similar
  electrical properties.
• Ionization is one way to quantify the electrical
  properties.
• Electronegativity is another way.

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Electronegativity

• When two atoms of the same element bond they form
  covalent molecules.
• Covalent because they share electrons
• When two atoms of different element form covalent
  bonds, the sharing might not be equal.

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Why dont some atoms share equally?

• Atomic Structure
• Some atoms are better at attracting electrons
  than others.
• The ability to attract electrons is known as
  electronegativity.

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Linus Pauling

• An American chemist created a scale for
  electronegativity.
• He assigned Florine an arbitrary value of 4.
• Florine is the most electronegative atom because
  it is able to attract electrons better than any
  other element.
• Electronegativity values for other elements where
  created based on a comparison to florine

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Electronegativity

• Can indicate the type of bond that will form.
• HOW?
• Think Tug-of-War

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Atoms of the Same Strength (Covalent)

• There is no winner.
• The two atoms share the electrons equally with
  each other.

Two atoms of similar strength
One or more electrons
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Atoms of Somewhat Different Strengths (Polar
Covalent)

• One atoms pulls the rope more than the other,
  neither wins.
• More rope is to one side of the line

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A Polar Covalent Bond

• Results in a molecule that has regions of
  positive charge and regions of negative charge.

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Atoms that have drastically different values

• The atom with greater electronegativity will win.
• Electron transfers from atom with low
  electronegativity to an atom with high
  electronegativity.
• Ions are formed.

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Atoms that have drastically different values

• The attraction between the two oppositely charged
  ions is called an Ionic Bond

High electronegativity
Low electronegativity
One or more electrons
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Indicating the bond type
Type of Bond Nonpolar Covalent Polar Covalent Ionic
Electronegativity difference lt 0.4 .4-2.1 gt 2.1
Diagram H----H H----Cl Na----Cl
Electrons Shared Equally Shared Unequally Transferred
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Molecule vs Compound

• Both terms mean the same concept.
• Molecule is the smallest unit of a covalently
  bonded compound.
• Molecules are covalently bonded atoms
• Ionic Compounds
• Formed by ionic bonding

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Assignment

• Write in your Planner or Table of contents!
• Ill be around to check before class is out.
• Page 135-139
• Reflect and Connect 1-4
• Due next class period