Transcript Unit 7: Bonding and Naming

Unit 7: Bonding and Naming
A Quick Review…
 Atoms are electrically neutral
 Ions
 Charged particles
 Anion
 Negative ion; gain electrons; nonmetals
 Cation
 Positive ion; lose electrons; metals
Unit 7 Objectives:
 Distinguish between ionic, covalent, and metallic
bonds
 Distinguish between ionic and molecular compounds
 Name ionic and molecular compounds
 Write formulas for ionic and molecular compounds
Bonds
 A valence electron from one atom is attracted to
another atom’s nucleus
 Remember…
 Everything
wants a full valence shell
 Everything wants to have lower Kinetic Energy
 Can tell the type using the atoms’ electronegativities,
or by the type of atoms involved
Ionic Bonds
 Electrons are donated from one
atom to the other
 Very different
electronegativities (difference is
>1.7)

One atom is MUCH more
attracted to electrons than the
other
 Which types of atoms are
involved?

Metals and non-metals – the metal
gives up electrons to the nonmetal
Covalent Bonds
 Electrons are “shared” by
two atoms
 Similar electronegativity
values (difference < 1.7)
 Closer electronegativities
means more equal
sharing
 What types of atoms are
involved?
 2 nonmetals
Covalent Bonds
 Atoms always share pairs of electrons
Type of Bond
Pairs Shared
Electrons
Shared
Single
1
2
Double
2
4
Triple
3
6
Metallic Bonds
 What type of atoms?
2
metals
 Metal cations
surrounded by a “sea of
electrons”
Determine the Bond Type
 H-O
 H-Cl
 Na-Cl
 K-Cr
 Na-Br
 C-H
Types of Compounds - Ionic
 Ionic Compounds
 Contain
ionic bonds
 Electrically Neutral
 A metal is joined to a non-metal or a polyatomic
ion
 Polyatomic Ion
 An ion made up of more than one element
 Covalently Bonded
 Almost always anions
Ex: SO42-
Types of Compounds - Ionic
 Law of Definite Proportions
 Small
whole number ratios
 The formula represents a formula unit (NOT a
molecule)
 Formula Units are always simplest ratio (REDUCE!)
 Ions surround each other so you can’t see which is
hooked to which
Types of Compounds - Molecular
 Contain covalent bonds
 Non-metals are joined to other non-metals
 Called molecules
 Smallest electrically neutral unit that still maintains the
properties of the substance
 Can be one type of atom – O2
 Can be a compound – CO2
Distinguishing Between Ionic and Molecular
Ionic
Molecular
Bond Type
Ionic
Covalent
Smallest
Piece
Formula Unit
Molecule
Types of
Elements
State of
Matter
Metal-Nonmetal
Nonmetal - Nonmetal
Metal –Polyatomic Ion
Solid
Solid, liquid, or gas
Chemical Formulas
 Show the kind and number of each type of atom in a
compound
 For molecules you can also say molecular formula
 Subscripts are used to tell you if there is more than
one of an atom. If there is only one, no subscript.


NaCl, BaS
CaCl2, C6H12O6
Diatomic Elements
 Some elements are never found as a single atom
 If they aren’t bonded to another type of atom, they
bond to themselves
 There are 7:
1.
2.
3.
4.
5.
6.
7.
Hydrogen (H2)
Nitrogen (N2)
Oxygen (O2)
Fluorine (F2)
Chlorine (Cl2)
Bromine (Br2)
Iodine (I2)
Oxidation State
 Remember the trend for the representative elements
 Transition Metals don’t always have the same
oxidation state
Naming Ions
 Two methods
Classical Method – uses root word (in Latin) +
suffixes (-ous, -ic).
 Fe2+ = Ferrous
 Doesn’t give the true value
 Doesn’t work for everything
2. Stock System – uses Roman numerals in ( ) to
indicate the numerical value.
 Fe2+ = Iron (II)
 Much better because it works all the time. We’ll use
this one
1.
Roman Numerals
Number
Roman
Numeral
1
I
2
II
3
III
4
IV
5
V
6
VI
7
VII
8
VIII
9
IX
10
X
 No, you don’t get
these on the test…
 Use with
transition metals
Naming Ions - Cations
 Use the stock system
 If the charge is always the same (representative
elements, Cd, Ag, Zn), just say the name of the
element followed by “ion”
 Example: Ca2+ = calcium ion
 If it is a metal that varies (transitions, Sn, Pb) say the
name of the element, the oxidation state as a Roman
Number, followed by “ion”
 Example: Mb2+ = molybdenum (II) ion
Naming Ions: Exceptions
 Representative elements that need Roman Numerals
 Pb
 Sn
 Transition metals that no not need a Roman
Numeral (bc they always have the same oxidation
state)



Ag1+
Cd2+
Zn2+
Naming Ions - Cations
Write the name of each cation
 Na1+
 Ca2+
 Al3+
 Fe3+
 Li1+
 Pb2+
 W6+
Writing Formulas- Cations
Write the formula for each ion.
 Potassium Ion
 Magnesium Ion
 Copper (II) Ion
 Silver Ion
 Mercury (II) Ion
 Chromium (VI) Ion
 Barium Ion
Naming Ions - Anions
 Anions always have the same oxidation state (no
need for Roman Numerals)
 Change the ending of the element to –ide
 Ex: F = Fluorine
F - = Fluoride Ion
Naming Ions - Anions
Name the following ions
 Cl 1 N 3 Br 1 O 2 Ga 3+
Writing Formulas - Anions
Write the formula for each ion
 Sulfide Ion
 Iodide Ion
 Phosphide Ion
 Strontium Ion
Polyatomic Ions
 Ions containing more than 1 element
 Almost always anions
 See list on the back of your Periodic Table or Packet
 No, You need not memorize them
 To name them, just check the list and use the name.
No change to the ending
Naming Ionic Compounds
 Binary Compounds only have 2 elements
 To write the name, just name the 2 ions
 NaCl - sodium chloride
 MgBr2 – magnesium bromide
Naming Binary Ionic Compounds
 A little harder with transition metals…

Don’t forget the Roman numerals
 Ex: CuO




Overall, the compound is neutral
We know O is 2Copper must be 2+
Copper (II) Oxide
 Ex: CoCl3




We know Cl is 1- and there are 3 of them
That makes 3Co must be 3+
Cobalt (III) Chloride
A Few More Examples
 Cu2S
 Sulfur is always:
 The Copper needs to add up to:
 There are 2 Copper atoms, so each one is:
 Name:
 Fe2O3
 Oxygen is always:
 There are 3 of them, which adds up to:
 The 2 Iron atoms should add up to:
 Each Iron is then:
 Name:
Name some Binary Ionic Compounds
 KCl
 Na3N
 CrN
 Sc3P2
 PbO
 PbO2
 Na2Se
Naming Ternary Ionic Compounds
 These have polyatomic ions. Name the cation, then
name the polyatomic ion

Ex: NaNO3
 Na = Sodium
 NO3 = Nitrate
 Sodium Nitrate
 The hardest part is remembering to check your list!
Name the Ternary Ionic Compounds
 LiCN
 Fe(OH)3
 (NH4)2CO3
 NiPO4
Writing Formulas for Ionic Compounds
 Remember, charges add up to ZERO
 Get the oxidation state of each piece
 Balance charges out by adding subscripts
 Polyatomic ions need ( ) if there is more than 1 of it
 Use the criss-cross method

Make the oxidation state of one the subscript of the other. Like
finding the least common multiple.
 Calcium
Chloride
Ca2+ Cl 1CaCl2
Write the formulas for these
 Lithium Sulfide
 Tin (II) Oxide
 Tin (IV) Oxide
 Magnesium Fluoride
 Copper (II) Sulfate
 Iron (III) Phosphide
 Gallium Nitrate
 Iron (III) Sulfide
 Ammonium sulfide
Keep in Mind…
 If you see ( ) it’s telling you the oxidation state of the
cation
 Anions generally end in –ide if it’s an element, and –
ate or –ite if it’s a polyatomic ion
Molecular Compounds
 Made of only Non-metals
 Electronegativities are similar, they aren’t being held
together by opposite charges
 This means we can’t use the oxidation state to see
how many of each atom we have
 The name will tell you the amount of each atom
using prefixes
Prefixes
1
Mono
2
Di
3
Tri
4
Tetra
5
Penta
6
Hexa
7
Hepta
8
Octa
9
Nona
10
Deca
Yes, memorize these!!
Naming Molecular Compounds
 To write the name:
Prefix + first element then Prefix + second element
 Only one exception this time: if the prefix on the first
element is “mono” we don’t write it
 No double vowels (oa, oo)

Rule of thumb: if it sounds weird, you need to drop a vowel
Name the Molecular Compounds
 N 2O
 NO2
 Cl2O7
 CBr4
 CO
 BaCl2
Write the Formulas for Molecular Compounds
 Diphosphorous pentoxide
 Tetraiodide nonoxide
 Sulfur hexafluoride
 Nitrogen trioxide
 Carbon trtrahydride
 Phosphorous trifluoride
 Aluminum chloride
Naming Acids
 We will save the nomenclature for acids until we
start talking about them.
 For now, here are a couple you should know:
Acid
Formula
Hydrochloric acid
HCl
Sulfuric Acid
H2SO4
Acetic Acid
CH3COOH