Ionic

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Ionic Covalent Compounds
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Chemical Bonds

• The force that holds two atoms together.

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2 types of bonds.

• Ionic
• Covalent

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Ionic Bond

• Forms between a metal and a nonmetal
• A positive ion (cation) and a negative ion (anion)

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Metal
Nonmetal
Ionic Bond
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Covalent Bond

• Covalent bonds occur between 2 nonmetals.
• The prefix co- means 2
• Think of co-workers

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Remember

• Elements tend to react to acquire a stable
  electron structure (8)
• The rule of octet

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The Formation Nature of Ionic Bonds
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• Ionic bond the force that holds oppositely
  charged particles together.
• Ionic compounds contain ionic bonds

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Binary Compounds

• Contain only two different elements
• Example
• NaCl
• Na Cl 2 different elements
• K2S
• 2 different elements

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Is this a binary compound?
This is Chlorine (Cl)
This is Sodium (Na)
Yes, this is binary! It has 2 different elements!
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Learning Check.

• Is MgO a binary compound?
• Yes
• No
• Is CaSO4 a binary compound?
• Yes
• No

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Energy the ionic bond

• Endothermic energy is absorbed during a
  chemical reaction.
• Exothermic energy is released during a chemical
  reaction.
• The formation of ionic compounds from and
  ions is almost always exothermic

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Names and Formulas for Ionic Compounds
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Formulas

• A formula is the symbols used to make up a
  compound.
• Ex NaCl sodium chloride
• Calcium chlorides formula is CaCl2. The 2 is a
  subscript, which means that it is written below.
• A subscript tells the number of atoms of the
  chemical written before it.

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• If a subscript is not present, then the subscript
  is assumed to be 1.
• Example Fe2O3
• There are two atoms of iron and three atoms of
  oxygen

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Ions and Ionic Bonds

• When an element loses electrons it gets a
  charge associated with it.
• Ex Mg2 means that magnesium now has a 2
  charge.
• Superscript means written above. The 2 written
  above Mg is the superscript.
• When a superscript is used, it tells the charge
  of the element.

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Oxidation Numbers

• The oxidation number shows how many electrons an
  element can accept, lose, or share when bonding.
• You need to know the pattern of the oxidation
  numbers across the periodic table

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Look at your periodic table and label the
oxidation numbers as follows
1
0
2
3 4 -3 -2 -1
These are the transition metals, and they have
varying oxidation numbers!
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Rules for Writing Binary Compounds

• 1. Write the symbol of the first element which
  has a positive oxidation number
• 2. Write the symbol of the element which has a
  negative oxidation number
• 3. Add subscripts so that the sum of the
  oxidation numbers of all the atoms is zero

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Example problem 1

• What is the formula for a compound containing
  only magnesium and chlorine?
• 1. Write the symbol of the element with the
  positive oxidation number followed by the symbol
  of the element with the negative oxidation number
  
• Mg Cl
• 2. Look up the oxidation numbers and write them
  above the symbols
• Mg2 Cl-1

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• 3. Now determine how many atoms of each element
  you need so that the sum of the oxidation numbers
  is zero
• Mg2 Cl-1
• 1 2
• 2 -2 0
• We need 2 chlorines for every 1 magnesium

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Example problem 2

• What is the formula for a compound containing
  only aluminum and sulfur?
• 1. Write the symbol of the element with the
  positive oxidation number followed by the symbol
  of the element with the negative oxidation number
  
• Al S
• 2. Look up the oxidation numbers and write them
  above the symbols
• 3 2-
• Al S

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• 3. Now determine how many atoms of each element
  you need so that the sum of the oxidation numbers
  is zero
• The least common multiple of 2 and 3 is 6
• Al3 S-2
• 2 3
• 6 -6 0
• Al2S3

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• Practice Problem 1
• Potassium and iodide
• K-1
• I1
• Therefore KI
• Name potassium iodide

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• Practice Problem 2
• Magnesium Chloride
• Mg2
• Cl1-
• Therefore MgCl2
• Name magnesium chloride

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Rules for Naming Binary Compounds

• 1. Write the name of the first element
• 2. Write the root of the second element
• 3. Add ide to the end of the second element

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Common Roots

• Chlorine chlor
• Fluorine fluor
• Nitrogen nitr
• Oxygen ox
• Phosphorous phosph
• Sulfur - sulf

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Example problem

• What is the name of Li2S?
• Write the name of the positive element
• lithium
• Write the root of the second element
• sulf-
• Add ide to the end of the second element
• Answer lithium sulfide

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• If the element has more than one oxidation
  number, then you must include the correct roman
  numeral within its name
• Example chromium (II) oxide is the name for the
  symbols CrO

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Compounds with Polyatomic Ions

• Poly- means many
• Polyatomic means having many atoms
• A polyatomic ion is a positively or negatively
  charged, covalently bonded group of atoms
• Ex ammonium NH4

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Compounds that contain polyatomic ions

• Polyatomic ions ions made up of more than one
  atom.
• Ex ammonium NH4
• Hydroxide OH-
• The charge given to a polyatomic ion applies to
  the entire group.

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• Never change the subscripts of the atoms within
  the ion.
• If more than one polyatomic ion is needed, place
  parenthesis around the ion and use subscript
  number.
• Ex magnesium chlorate Mg(ClO3)2

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Polyatomic Ions to Know

• Ammonium NH4
• Acetate C2H3O2-
• Chlorate ClO3-
• Hydroxide OH-
• Nitrate NO3-
• Carbonate CO32-
• Sulfate SO42-
• Phosphate PO43-

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• Practice Problem 1
• Ammonium chloride
• NH4 Cl-
• Because charges (1 -1)
• NH4Cl

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• Practice Problem 2
• Calcium chlorate
• Calcium Ca2 Chlorate ClO3-
• How many Ca will it take to chlorate? 2
• Therefore Ca(ClO3)2

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Covalent Bonding
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What is a Covalent Bond?

• The chemical bond that results from the sharing
  of valence electrons.
• In a covalent bond the shared electrons are
  considered to be part of the complete outer
  energy level of both atoms involved.
• Generally occurs between elements close to each
  other on the periodic table.
• Between 2 nonmetals

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Diatomic Molecules

• Hydrogen, Oxygen, Bromine, Iodine, Chlorine,
  Fluorine, and Nitrogen occur in nature as
  diatomic molecules, not single atoms.
• A diatomic molecule is a molecule of the same
  atom bonded to itself to make it more stable.

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Double Triple Covalent Bonds

• Double bonds occurs when two pairs of electrons
  are shared.
• Ex two O atoms
• O2
• A triple bond occurs when three pairs of
  electrons are shared.
• Ex three N atoms
• N3

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Strength of Covalent Bonds

• Some covalent bonds can be broken, some more
  easily than others.
• It depends upon their strength.

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What controls the strength of covalent bonds?

• 1 Bond length ( the distance between the
  bonded nuclei)
• It is determined by the size of the atoms and how
  many electron pairs are shared
• AS THE NUMBER OF SHARED ELECTRON PAIRS INCREASES,
  BOND LENGTH DECREASES

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• A triple bond ( with 3 shared pairs) has a
  shorter bond length than a single bond ( only 2
  electrons shared)
• THE SHORTER THE BOND LENGTH, THE STRONGER THE
  BOND

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In Conclusion

• SINGLE BONDS ARE WEAKER THAN DOUBLE BONDS, WHICH
  ARE WEAKER THAN TRIPLE BONDS.

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• Energy is released when a covalent bond forms.
• Energy must also be added to break the bonds in a
  molecule
• Bond Dissociation Energy (BDE) the amount of
  energy required to break a specific covalent
  bond. Always a positive value

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Naming Covalent Molecules
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Binary molecular compounds

• Binary molecular compounds are composed of two
  different nonmetals.

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3 Simple Rules for Naming Binary Molecular
Compounds

• 1st the first element in the formula is always
  named first, using the entire element name.
• 2nd The second element in the formula is named
  using the root of the element and adding the
  suffix ide.
• 3rd Prefixes are used to indicate the number of
  atoms of each type that are present in the
  compound.

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Some Common Prefixes

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• FOR EXAMPLE
• P2O5
• Phosphorous oxide
• (now add the prefixes)
• Diphosphorous pentoxide

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Exceptions to every rule

• The first element in the formula never uses the
  prefix mono-
• To avoid awkward pronunciation, drop the final
  letter in the prefix when the element name begins
  with a vowel.
• Ex CO carbon monoxide, not monocarbon monooxide

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Naming Acids
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Naming Acids

• Binary Acids contain Hydrogen and one other
  element.
• Use the prefix hydro- to name the hydrogen part
  of the compound.
• The rest of the name consists of a form of the
  root of the second element plus the suffix ic,
  followed by the word acid.
• Ex HBr hydrobromic acid

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Oxyanions? Oxyacids?

• Oxyanion polyatomic ion that contains oxygen.
• Oxyacid any acid that contains hydrogen and an
  oxyanion

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Rules for Naming Oxyacids

• 1st identify the anion present (remember this
  is the one that gains electrons, has a neg
  charge)
• 2nd if the anion suffix is ate, replace it
  with the suffix ic
• 3rd if the anion ends in ite, replace it with
  -ous
• 4th follow with the word acid

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Lets practice

• HNO3
• NO3- nitrate
• According to the rules it will become nitric
• Add the word acid to the end
• The Answer nitric acid

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• HNO2
• NO2- nitrite
• According to the rules, nitrite becomes nitrous
• Therefore, the answer is nitrous acid
• NOTICE THAT THE HYDROGEN IN AN OXYACID IS NOT
  PART OF THE NAME

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Writing Formulas from Names

• Subscripts are determined from the prefixes used
  in the name because the name indicates the exact
  number of each atom present in the molecule.

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Look at the formula of the molecule
Is the compound an acid? (contains H, or contains
a polyatomic ion that contains O)
Yes
No
Name as an acid. Is there Oxygen in the compound?
Name the 1st element in the molecule. Use prefix
if the number of atoms is greater than one. To
name the second element, indicate the number
present by using a prefix root of second
element -ide.
Yes
No
Root of oxyanion present, -ic, if the anion
ends in ate, or ous. If the anion ends in ite,
then acid.
Hydro root of 2nd element -ic, then acid
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Polarity
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Polarity

• The arrangement of the atoms in some molecules is
  such that one end of the molecule has a positive
  electrical charge and the other side has a
  negative charge.

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Water

• Water is a polar molecule because of the way the
  atoms bind in the molecule such that there are
  excess electrons on the Oxygen side and a lack or
  excess of positive charges on the Hydrogen side
  of the molecule.

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• Water is a polar molecule with positive charges
  on one side and negative on the other

More Positive Charges
More Negative Charges