Chemical Bonding

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Chemical Bonding
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Electron Configuration in Ionic Bonding

• Valence Electrons are electrons in the highest
  occupied energy level of an atom
• These electrons determine the chemical properties
  of an element

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Electron Configurations in Ionic Bonding

• Valence electrons can be determined by looking at
  the elements electron configuration
• Ex carbon is 1s22s22p2 or He2s22p2
• Valence e- 2 2 4

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Electron Configurations in Ionic Bonding

• Valence electrons are usually the only ones used
  in bonding
• These can be shown on electron dot structures

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Electron Configurations in Ionic Bonding

• Octet Rule in forming compounds, atoms tend to
  achieve the electron configuration of a noble gas
• All noble gases (except He) have eight valence
  electrons (s2p6)

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Electron Configurations in Ionic Bonding

• Metals (elements on the left side of the periodic
  table) tend to form cations
• This is because it is easier to lose 1,2,3 or
  electrons than to gain 5,6,7

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Electron Configurations in Ionic Bonding

• Nonmetals (elements on the right side of the
  periodic table) tend to form anions
• This is because it is easier to gain 1,2,3
  electrons than to lose 5,6,7

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Electron Configurations in Ionic Bonding
Group Electron Config Valence electrons Ionic Charge
1 s1 1 1
2 s2 2 2
13 s2p1 3 3
14 s2p2 4 NONE
15 s2p3 5 -3
16 s2p4 6 -2
17 s2p5 7 -1
18 s2p6 8 NONE
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Formation of Ionic Bonds

• An ionic bond is the transfer of electrons, which
  results in two ions of opposite charge attracting
  to one another
• Ex Na will give up one electron to Cl so that
  you have Na and Cl-, which are then attracted to
  one another forming NaCl

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Naming Ions

• Cations same element name, just add the word
  ion on the end
• Ex Na sodium ion
• Anions change the ending to -ide and add the
  word ion on the end
• Ex Cl- chloride ion

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Naming Ionic Compounds

• When naming an ionic compound, name the cation,
  then the anion (left to right)
• Ex NaCl sodium chloride
• K2O potassium oxide
• The fact that there are numbers doesnt affect
  anything (unless they are transition metals)

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Naming Ionic Compounds

• To go from the name to the symbols, you need to
  know the ionic charges
• Ex give the symbol for lithium nitride
• Lithium is Li and nitride is N3-
• THE CHARGES MUST BALANCE!!
• Therefore, there must be 3 lithiums for every
  nitrogen Li3N

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Naming Ionic Compounds

• Transition metals usually form more than one
  cation
• When naming compounds containing transition
  metals, a roman numeral is used to indicate the
  charge
• Ex CuCl copper (I) chloride
• CuCl2 copper (II) chloride

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Naming Ionic Compounds

• Polyatomic Ions an ion consisting of more than
  element all of these elements work together as
  one unit and the entire unit has a specific
  charge
• These have special names that need to be
  memorized
• Naming is done in the same fashion

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Naming Ionic Compounds

• Ex CO32- is called carbonate
• What would the formula for calcium carbonate be?
  Lithium carbonate? Aluminum carbonate?
• CaCO3
• Li2CO3
• Al2(CO3)3
• CHARGES MUST STILL BE BALANCED

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Covalent Bonding

• Covalent Bonding takes place between two
  non-metals and involves a sharing of electrons to
  obtain an octet
• Electrons that do not take place in the bond are
  called unshared pairs

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Covalent Bonding

• Sometimes atoms will form multiple bonds to
  achieve stable configurations
• Double bonds involve 4 electrons being shared,
  and triple bonds involve 6 electrons being shared

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Covalent Bonding

• Single bonds are the longest, followed by double,
  then triple
• Triple bonds are the strongest, followed by
  double, then single

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Covalent Bonding

• Some elements are typically found in nature
  covalently bonded to another atom of the same
  element. These are called diatomic elements
• Ways to remember these 7
• BrINClHOF (brinkelhoff)
• I Bring Clay For Our New House

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Naming Molecules

• Covalent compounds are also known as molecules.
• Unlike ionic compounds, which would only form in
  one way, many different molecules can form from
  the same elements

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Naming Molecules

• For example, what is the difference between CO
  and CO2?
• These are different compounds, but how would that
  be reflected in their name?
• Answer by using numerical prefixes

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Naming Molecules

• The prefixes are

Number Prefix
1 mono
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
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Naming Molecules

• CO has one C, one O gt carbon monoxide
• CO2 has one C, two O gt carbon dioxide

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Naming Molecules

• Both elements in the compound need to have a
  prefix unless the first one is mono, then it
  can be dropped
• Ex P2O5 diphosphorus pentaoxide
• PO5 phosphorus pentaoxide (no mono needed on
  the first element)

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Naming Acids

• Acids are compounds that contain a hydrogen ion,
  and their name comes from the anion to which the
  hydrogen is bonded
• If it is bonded to a monatomic ion, the prefix
  hydro is added and the ending becomes ic HCl
  is hydrochloric acid

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Naming Acids

• If the anion is a polyatomic ion, no hydro prefix
  is added.
• If the ion ends in ate the ending changes to
  ic
• Ex HNO3 (anion is nitrate) nitric acid
• If the ion ends in ite the ending changes to
  ous
• Ex HNO2 (anion is nitrite) nitrous acid

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Naming Hydrates

• Hydrates are compounds that include water (H2O)
  in their structure
• Ex CuSO4 5H2O
• Name the base portion first copper (II) sulfate
• Name the hydrate portion second pentahydrate
• Copper (II) sulfate pentahydrate

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Metallic Bonding

• Bonds between metals atoms are called metallic
  bonds
• A metallic bond consists of the positive nuclei
  of the metal atoms in a sea of electrons

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Properties of Ionic Compounds

• Ionic compounds tend to be
• Hard
• Brittle
• Have high boiling/melting points

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Properties of Molecules

• Molecules can be either polar or nonpolar
• In a polar covalent bond, electrons are shared
  unequally
• In a nonpolar covalent bond, electrons are shared
  equally

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Properties of Molecules

• Polarity of bonds can be determined using
  electronegativity differences (listed in a table)
• If the difference is 0-0.4, the bond is nonpolar
  covalent. If the difference is 0.5-2.0, the bond
  is polar covalent. If the difference is 2.1 or
  greater, the bond is ionic

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Properties of Metals

• Metals are
• Shiny
• Malleable (can be hammered into shapes)
• Ductile (can be drawn out into wires)

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Properties of Metals

• Alloys are mixtures of metals that have
  properties of both metals
• Ex bronze, brass, sterling silver