Chapter 4 Section 2 Notes

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Chapter 4 Section 2 Notes

• Ionic and Covalent Bonding

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What holds bonded atoms together?

• Atoms bond when their valence electrons interact
• Atoms with full outermost energy levels are less
  reactive (Noble Gases)
• Atoms with partially filled energy levels are
  more reactive (Groups 1-17)
• Goal of atoms have a full outer energy level

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What holds bonded atoms together?

• Octet Rule atoms tend to gain, lose, or share
  electrons so they have 8 electrons in their outer
  shell.
• The positively charged nucleus attracts the
  negatively charged electrons this bond holds 2
  atoms together.
• Bonds behave like flexible springs instead of
  like sticks

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Electrons in Shells

• Electrons are placed in shells according to
  rules
• 1st shell can hold up to 2 electrons
• 2nd shell can hold up to 8 electrons
• 3rd shell can hold up to 18 electrons, but after
  8, you move to the 4th shell

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• Na would like to lose 1 electron
• N would like to gain 3 electrons
• O would like to gain 2 electrons

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Electron Dot Diagrams

• Symbols of atoms with dots to represent the
  valence-shell electrons
• 1 2 13 14 15 16
  17 18
• H? He
• ? ? ?
  ? ? ? ? ? ?
  ? ?
• Li? Be? ? B ? ? C ? ? N ?
  ? O ? F ? Ne
• ?
  ? ? ? ? ?
  ? ?
• ? ? ?
  ? ? ? ? ? ?
  ? ?
• Na? Mg? ? Al? ? Si ? ?P?
  ?S? Cl ? Ar
• ?
  ? ? ? ? ?
  ? ?

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Ionic Bonds

• Ionic Bond formed when metals react with
  nonmetals electrons are transferred
• Metals lose electrons to form POSITIVELY charged
  ions, or cations
• Examples Lithium, Sodium, Beryllium, Magnesium
• Positive ions form when the number of electrons
  are less than the number of protons
• Group 1 metals ? ion1
• Group 2 metals ? ion2
• Group 13 metals ? ion3

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Ionic Bonding One big greedy thief dog!!
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Formation of Sodium Ion

• Sodium atom Sodium ion
  
• Na ? e? ??? Na
• 2-8-1 2-8 ( Ne)
• 11 p 11 p
• 11 e-
  10 e-
• 0
  1

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Formation of Magnesium Ion

• Magnesium atom Magnesium ion
• ?
• Mg ? 2e? ?? Mg2
• 2-8-2 2-8 (Ne)
• 12 p 12 p
• 12 e-
  10 e-
• 0
  2

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Some Typical Ions with Positive Charges (Cations)

• Group 1 Group 2 Group 13
• H Mg2 Al3
• Li Ca2
• Na Sr2
• K Ba2

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Quick Quiz 1

• A. Number of valence electrons in aluminum
• 1) 1 e- 2) 2 e- 3) 3 e-
• B. Change in electrons for octet
• 1) lose 3e- 2) gain 3 e- 3)
  gain 5 e-
• C. Ionic charge of aluminum
• 1) 3- 2) 5- 3) 3

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Quiz Quiz 1 Answers

• A. Number of valence electrons in aluminum
• 3) 3 e-
• B. Change in electrons for octet
• 1) lose 3e-
• C. Ionic charge of aluminum
• 3) 3

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Quick Quiz 2

• Give the ionic charge for each of the following
• A. 12 p and 10 e-
• 1) 0 2) 2 3) 2-
• B. 50p and 46 e-
• 1) 2 2) 4 3) 4-
• C. 15 p and 18e-
• 2) 3 2) 3- 3) 5-

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Ionic Bonds

• Nonmetals gain electrons to form NEGATIVELY
  charged ions, or anions
• Examples Oxygen, Sulfur, Fluorine, Chlorine
• Negative ions form when the number of electrons
  is more than the number of protons
• Group 15 nonmetals ? ion-3
• Group 16 nonmetals ? ion-2
• Group 17 nonmetals ? ion-1

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Ionic Bonds

• Electrons are transferred in ionic bonding
• One atom gains electrons, and the other atoms
  loses electrons

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Ionic Bonds

• Example Sodium loses one electron to get a 1
  charge (Na). Chlorine gains an electron to get
  a -1 charge (Cl-). Then, the oppositely charged
  ions attract each other and form a bond.

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Ionic Bonds
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Ionic Bonds

• Ionic compounds are in the form of network
  structures they therefore have high melting and
  boiling points because of the high amount of
  energy required to pull apart the bonds

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Ionic Bonds

• Ratio of Ions
• The chemical formula NaCl tells us there is 1 Na
  ion and 1 Cl- ion, forming a neutrally charged
  particle.
• Since there is only one atom of each element,
  there is a 11 ratio
• The chemical formula CaF2 tells us there is 1
  Ca2 ion and 2 F- ions. 2 F- ions are needed to
  balance out the 2 charge so the particle is
  neutral

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Ionic Bonds

• Electricity
• Solid ionic compounds dont conduct electricity
• When dissolved in water, ionic compounds conduct
  electricity because the ions are free to move

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Metallic Bonds

• Metallic Bond a bond formed by the attraction
  between positively charged metal ions and the
  electrons around them.
• Occurs between atoms of metal elements

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Metallic Bonds

• The attraction between the nucleus and the
  neighboring atoms electrons holds the atoms
  close together
• Since the atoms are packed closely, the electrons
  move from atom to atom, which is why
• Metals conduct electricity
• Metals are flexible and bend without breaking
  (ductile and malleable)

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Covalent Bonds

• Covalent Bond a bond formed when atoms share one
  or more pair of electrons
• Often made of molecules
• Formed between nonmetal atoms
• Atoms joined by covalent bonds share electrons

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Covalent Bonds

• There are 2 types of covalent bonds
• Nonpolar covalent bonds electrons are shared
  equally often occurs between 2 atoms of the same
  element
• Polar covalent bonds electrons are shared
  unequally often occurs between 2 atoms of
  different elements shared electrons are
  attracted to the nucleus of 1 atom more than the
  other
• Usually, electrons are more attracted to atoms of
  elements located to the right and closer to the
  top of the periodic table

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Nonpolar Covalent Bond
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Polar Covalent Bond
Note Partial charges occur with polar covalent
bonds
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Structural Formulas

• When writing structural formulas
• 1 line drawn indicates that atoms share 1 pair,
  or 2 electrons
• Example Cl-Cl
• 2 lines drawn indicate that atoms share 2 pair,
  or 4 electrons
• Example OO
• 3 lines drawn indicate that 3 pair, or 6
  electrons are being shared

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Polyatomic Ions

• A polyatomic ion is an ion made of 2 or more
  atoms that are covalently bonded and that act
  like a single ion
• Some polyatomic anion names relate to their
  oxygen content
• An anion ending in ate is the ion with one more
  oxygen atom
• An anion ending in ite is the ion with one less
  oxygen atom
• Examples Sulfate (SO4-2) and Sulfite (SO3-2)