Transcript Chemical Bonds - coellochemistry

Chemical Bonds
To Bond or Not to Bond?

Why do atoms want to bond? (Hint: You
already know the answer)
To Bond or Not to Bond?
 Octet
rule: all elements want to
obtain 8 valence electrons and
become stable
Metallic Bonding

Bond between two metals

Produces an alloy
 Alloy:
solid solution of two or more metals
(ex: Steel)
Ionic Bond

Electrostatic attraction: attraction between
positive and negative charge

Gains or loses valence electrons

Bond between a metal and nonmetal
Ionic Compound
Between a METAL and a NONMETAL
 Between a POSITIVE and a NEGATIVE
ion

 Ion-
a charged atom or group of atoms
 Charges between metal and nonmetal must
equal ZERO

Most are CRYSTALLINE solids
Naming Ionic Compounds
 The
metal is named just as you
see it off the periodic table
 The
nonmetal has the ending
dropped and replaced with –ide
Practice

MgCl2

KCl

Be3N

Cs2S
Writing Ionic Formulas

Label the Parts:
MgCl2

Steps:
 1.
Write the Element symbols
 2. Write each elements charge
 3. Determine subscripts by making overall
charge of the compound equal zero!
 4. Reduce if possible. All Subscripts (other
than 1) must be written
Li combines with S
Practice
K – Br
 Ca – P
 Sr – O
 Li – Cl
 Sodium fluoride
 Beryllium iodide
 Magnesium oxide

Polyatomic Ions

Polyatomic ions: groups of atoms that
have a charge
 List

of Polyatomics given today
When using polyatomic ions you must use
parenthesis if there is more than 1 of
them.
Ca(OH)2
Naming Ionic Bonds with
Polyatomics

Name the metal as always. Name the
polyatomic just the way the name is on
your list.
 Ca(OH)2
 BaSO4
 Na3PO4
 (NH4)CO3
 Mg(ClO3)2
Writing Formulas

Must protect polyatomic with parenthesis
if it is more than 1!
 Calcium
carbonate
 Lithium hydroxide
 Strontium acetate
 Potassium chromate
 Barium nitrate
Transition Metals

Most Transition metals have multiple
oxidation numbers
Zn+2, Cd+2, Ag+1
 Reverse Exceptions: Pb and Sn need roman
numerals
 Exceptions:

Must write transition metals with there
oxidation number displayed in parenthesis
using roman numerals
 Example:
Iron (II) bromide
Roman Numerals
One (I)
 Two (II)
 Three (III)
 Four (IV)
 Five (V)
 Six (VI)
 Seven (VII)
 Eight (VIII)

Practice

Silver nitride

ZnCl2

iron (II) hydroxide

CoN

Lead (IV) nitrate

Fe3N2

Iron (III) bromide

PbSO4
Mixed

Strontium acetate

CoN

Copper (III) chromate

ZnCl2

Magnesium bromide

Na3PO4

Li2O
Covalent Bonds
Share electrons: all elements want 8
valence electrons (***except H and He want
2 valence electrons***)
 The sharing of covalent compounds gives
them different geometrical shapes
 Between a NONMETAL and a NONMETAL
 Two Types:

 Non-polar-
equal sharing of electrons
 Polar- unequal sharing of electrons
Naming Covalent Compounds
For covalent compounds both of the
nonmetals must have prefixes assigned
to represent the number of atoms
 The second element has a prefix and has
the ending changed to -ide
 One- mono
Six- hexa
 Two- di
Seven- hepta
 Three- tri
Eight- octa
 Four- tetra
Nine- nona
 Five- penta
Ten- deca

Practice Naming Covalent
Compounds

CO

CO2

N2O5

NF3
Practice Writing Covalent
Compounds

Iodine pentafluoride

Nitrogen tribromide

Diphosphorus pentoxide

Sulfur hexachloride
Diatomic Molecules

Molecule: another name for covalent
bonds

Diatomic molecule: covalent compounds
between two of the same atoms
 Seven
N2, H2
you need to know: I2, Br2, Cl2, F2, O2,
Lewis Dot for Covalent
Compounds

Lewis Dot Review: What is a Lewis dot
diagram?

Draw the Lewis dot for the following:
S
N
C
Xe
He
Lewis Dot for Covalent
Compounds
What does every element want?
 We must draw the Lewis dot diagram so every
element is SHARING 8 valence electrons
(EXCEPT: H only needs 2 valence e-)
 Covalent compounds can create:

 Single
bonds: one line drawn and represents 2 valence
electrons
 Double bonds: two lines drawn and represents 4 valence
electrons
 Triple bonds: three lines drawn and represents 6 valence
electrons
Lewis Dot for Covalent
Compounds

Steps: (NAS)
 1.
NEED: calculate how many total electrons
you will need if everyone had 8
 2. AVAILABLE: calculate the electrons you
have to work with using your valence electron
trend from the periodic table
 3. SUBTRACT: Need – Available = how many
bonds are needed
Examples:
VSEPR Theory

VSEPR: Valence Shell Electron Pair
Repulsion Theory

Definition: in covalent compounds the
geometric arrangement is determined
solely by the repulsions between electron
pairs present in the valence electron shell
 To
determine shape you must first draw the
Lewis dot diagram
VSEPR Shapes

Linear

2
bonding atoms
(regions)
 0 lone pairs
Tetrahedral
4
bonding atoms
 0 lone pairs

Trigonal planar
3
bonding atoms
 0 lone pairs
Polar vs. Nonpolar

Polar
 In
a polar molecule
there will be at least
one lone pair for the
central atom

Nonpolar
 Nonpolar
molecule
has 0 lone pairs from
the central atom
Ionic vs. Covalent



Ionic
Very strong bonds
Melt at very high
temperatures
Crystal structures
called salts and many
can dissolve in water



Covalent
Weaker bonds
Melt at very low
temperatures
Most cannot dissolve
in water
Determine Type of Bond






K – Br
S–O
Si – Cl
H–F
Se – S
H–O






Na – Cl
Fe – S
H–N
Ca – I
Al – O
Mg - Br