Chapter 7 Atoms

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Chapter 7 Atoms Bonding
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What is Chemical Bonding?

• Chemical Bonding (def) the combining of atoms
  of elements to form new substances.
• The rules of chemical bonding are determined by
  the structure of the atoms involved in the bond.

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Lets Review a Little

• Protons are positively charged and are located in
  the nucleus.
• Neutrons have no charge (neutral) and are located
  in the nucleus.
• Electrons are negatively charged and are located
  in the electron cloud surrounding the nucleus.
• The electron cloud has energy levels called
  shells.

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Lets Review a Little

• Electron Shells
• K Shell holds 2 electrons
• L shell holds 8 electrons
• M shell holds 8 electrons
• (Actually the M shell can hold up to 18
  electrons, but youll learn more about that in
  chemistryalong with the N, O, P and Q shells)

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Lets Review a Little

• The outermost electron shell is called the
  valence shell.
• The number of electrons in the valence shell
  determines how the atom will bond with another
  atom.
• The electrons in the valence shell are called
  valence electrons.

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Why do Atoms Bond?

• It is an atoms goal to be as stable as possible.
• For an atom to be stable, it must have a full
  outer shell.
• Once an atoms outer shell is full, the atom is
  stable and it will not seek out another atom to
  bond with because it doesnt need any more
  electrons its outer shell is full.

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Why do Atoms Bond?

• The electron arrangement of the outermost energy
  level of an atom determines whether or not the
  atom will form chemical bonds.
• For example, the noble gases do not form chemical
  bonds because their outer shells are full, so
  they are stable.
• They are known as inert gases.

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Why do Atoms Bond?

• Atoms of elements other than the Noble Gas Family
  do not have filled outermost energy levels
  (shells).
• Because of this, they bond with other atoms to
  ensure that their outermost energy levels are
  full.
• There are a few ways that atoms are able to do
  this.
• This is chemical bonding.

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Atoms Want Stability!!!

• Octet Rule
• (Oct like octopus 8 legs)
• most atoms form bonds in order to have 8 valence
  e-
• They want a full outer energy level
• like the Noble Gases!

• Stability is the driving force behind bond
  formation!

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1. Ionic Bonds
Rule electron e-

• Ionic Bonds (def) Bonding that occurs because
  of the transfer of electrons.
• Ions - charged atoms
• either neg (-) or pos ()
• formed by transferring e-from a metal to a
  nonmetal
• The metal gives an e- and the nonmetal receives
  an e-.

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1. Ionic Bonds

• Before
• Is either atoms outer shell full?

• After
• Are their outer shells full now?

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1. Ionic Bonds

• What holds the atoms together is their opposite
  charges.
• Remember, opposites attract!!!!

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Important Vocabulary of Ionic Bonds You Should
Know

• Ion a charged atom ( or -)
• Ionic Bonding Involves the transfer of
  electrons to bond atoms, some atoms gain
  electrons and other atoms lose electrons.
• Ionization the process of removing electrons
  and forming ions. Energy is required for this
  process to occur.
• Ionization Energy the energy required to form
  ionic bonds.
• When an electron is removed from an atom, the
  atom absorbs energy
• When an electron is gained by an atom, the atom
  releases energy.
• Oxidation Number the charge on the atom after
  it gains or loses electrons in the process of
  chemical bonding.
• Valence electrons the number of electrons in
  the outermost shell of an atom.
• Electron affinity the tendency of an atom to
  attract electrons.

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A. Properties of Ionic Bonds

• Ions form a 3-D crystal lattice
• This is because the ions are arranged in a
  specific way due to the way opposite charges
  attract and same charges repel.

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A. Properties of Ionic Bonds

• Crystal lattice gives ionic compounds great
  stability. (strong)
• Different shaped crystal lattices also give ionic
  compounds interesting crystal shapes.
• There are 6 basic crystal shapes.
• These shapes help geologists identify minerals
  because 1 of the 5 must-have properties of
  minerals is that they have a crystalline
  structure.
• Ionic compounds also tend to have high melting
  points.

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2. Covalent Bond

• Covalent Bond (def) bonding in which
  electrons are shared rather than transferred.
• Co both
• Valent valence shell

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2. Covalent Bond

• In covalent bonding, the positively charged
  nucleus of each atom simultaneously (at the same
  time) attracts the negatively charged electrons
  that are being shared.
• The electrons spend most of their time between
  the atoms
• The attraction between the nucleus and the shared
  electrons holds the atoms together.

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Properties of Covalent Bonds

• (def) The combination of atoms formed by a
  covalent bond is a Molecule.
• Mole-cule means little lump.
• (Mole lump, cule small)
• A molecule is the smallest particle of a
  covalently bonded substance that has all of the
  properties of that substance.

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Electron Dot Diagrams

• Electron Dot Diagrams can be used to show how
  ionic and covalent bonds either transfer or share
  electrons.
• In an electron dot diagram
• The chemical symbol represents the nucleus and
  all inner electron shells.
• The dots represent the number of valence
  electrons in the outermost electron shell
  (valence shell)

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Electron Dot Diagrams

• Transferring e- (ionic bonds)

• Sharing e- (covalent bonds)

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Electron Dot Diagrams
These show the electron dot diagrams of some
common elements
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Comparison Chart
IONIC
COVALENT
transferred from metal to nonmetal
shared between nonmetals
Electrons
Melting Point
high
low
Soluble in Water
yes
usually not
yes (solution or liquid)
Conduct Electricity
usually no
crystal lattice of ions, form crystalline solids
molecules, odorous liquids gases
Other Properties
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3. Metallic Bonds

• Metals are elements that give up electrons easily
• In a metallic solid, only atoms of that
  particular element are present (it is made of
  only one element)
• In a metallic bond, the outer electrons of the
  atoms form an electron cloud or a sea of
  electrons.
• All of the electrons become the property of all
  of the atoms so they can all fill up their outer
  shells.

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3. Metallic Bonds

• Because of the sea of electrons that the
  metallic bond produces, metals have very special
  properties
• They are malleable
• They are ductile
• They conduct electricity very well.
• They have a high melting point.

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Comparing the Types of Bonds

• Link to Dog Bone Bonding Analogy
• Ionic bonds One big greedy thief dog!
• Covalent bonds  Dogs of equal strength.
• Polar Covalent bonds Unevenly matched but
  willing to share.
• Metallic bonds  Mellow dogs with plenty of bones
  to go around.