UNIT 5 CHEMICAL BONDING
Chapter 6.1 Lewis Dot Diagrams & Ions
STABLE ELECTRON CONFIGURATIONS
 When

is an atom unlikely to react?
When the outer shell (highest occupied
energy level) is filled with electrons
 8 e for Octet Rule
 Noble
gases are the most stable
elements.
The highest occupied energy level is
completely filled.
 Elements tend to react to achieve electron
configurations similar to those of noble
gases.

STABLE ELECTRON CONFIGURATIONS
 Chemical
properties of an element
depend on the number of valence
electrons.
 Electron dot diagram - [Lewis Dot
Model] is alternative to standard
electron shell diagram

Dot diagram emphasizes valence
electrons (inner shells hidden)
ELECTRON CONFIGURATION AND
LEWIS DOT DIAGRAMS
F
F
Lewis Dot
Diagram
Both of these mean the same thing
LEWIS DOT DIAGRAM
Element
symbol represents:
 Nucleus
AND
 All inner core electrons
Dots
F
represent:
 Valence
electrons (outer shell –
Highest occupied energy level)
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
STABLE ELECTRON CONFIGURATIONS –
LEWIS DOT DIAGRAMS
FORMATION OF IONS
 When
an atom gains or loses an electron(s)
 atom is no longer neutral.

# of Protons NO LONGER EQUAL # of
electrons
Definition:
 ION = atom (or group of atoms) with
positive (+) or negative (-) net electric
charge.
FORMATION OF IONS
 ANION

= Ion with a negative (-) charge
[Memory aid: anion = A Negative ION]
 Example:
Chlorine
atomic # 17
 Halogen Family/Group 7A




Neutral (but not stable) - 17 protons and 17
electrons
To become stable – gain 1 electron in outer e- shell


7 Valence Electrons
Now have 1 more e- than proton = -1 net charge
Symbol is written Cl- or Cl1-
FORMATION OF IONS
 Naming
Part

Cl-
Anions:
of element name + suffix “ide”
Example: Chlorine ion becomes “chlor” + “ide”
is called a chloride ion
 F- is the fluoride ion (“fluor” + “ide”)
 Br- is the bromide ion (“brom” + “ide”)
 I- is the iodide ion (“iod” + “”ide”)
FORMATION OF IONS
 CATION
= Ion with a positive charge
 Example: Sodium
atomic # 11
 Alkali Metal Family/Group 1A

1 Valence Electron
Neutral (but not stable) -11 protons and 11 electrons




To become stable – lose the 1 electron in outer e- shell
 Now has 1 more proton than electron = 1+ net
charge
Symbol is written Na+ or Na1+
FORMATION OF IONS
 Naming
Use
Cations:
the normal element name
Na+ is called a sodium ion
 Li+ is the lithium ion

 Cs+ is
the cesium ion
 Fr+ is the francium ion
BONDING
 Elements
achieve stable electron
configurations by transferring or sharing
electrons between atoms
 Transferring Electrons  Those with <4 valence electrons “LEND”
them

These elements “lose” valence electrons
OR

Those with >4 valence electrons “BORROW”
them

These elements “gain” electrons
FORMATION OF IONS & BONDING
Sodium reacts with chlorine 
electron transferred from sodium to chlorine
 Each atom ends up more stable

FORMATION OF IONS & BONDING
Sodium reacts with chlorine 
electron transferred from sodium to chlorine
 Each atom ends up more stable

FORMATION OF IONS & BONDING
Sodium reacts with chlorine 
electron transferred from sodium to chlorine
 Each atom ends up more stable

FORMATION OF IONS & BONDING
Sodium reacts with chlorine 
electron transferred from sodium to chlorine
 Each atom ends up more stable

IONIC BONDING
 Chemical
bond = force that holds atoms or
ions together as a unit.
 Opposites

Particle(s) with negative charge attracts particle(s)
with positive charge.
Ionic
•
•
attract
bond
Force that holds cations and anions together and
which involves the transfer of electrons.
Bond occurs between a metal and a nonmetal
IONIC BONDING

Ionic Compounds

What is the chemical formula for magnesium
chloride?


Mg and Cl
First determine the Lewis Dot Diagram and Ions
for each element:
Ions
Mg2+ ,
Cl-
Lewis Dot
IONIC BONDING
 Mg
atom cannot reach a stable electron
configuration by giving up just 1 valence
electron or reacting with just 1 chlorine
atom.
Mg + 2Cl
OR
IONIC BONDING
Mg
transfers 2 electrons, one to each of the
2 Cl atoms.
 After transfer 
Charge on the magnesium ion is 2+
 Charge on the 2 chloride ions is 1
IONIC BONDING

Formula for magnesium chloride is MgCl2
-
2+
-
PROPERTIES OF IONIC COMPOUNDS
 The
properties of sodium chloride
are typical of ionic compounds.

High melting point

sodium chloride melts ~800°C
When solid - poor conductor of electric
current
 When liquid (melted) - good conductor
of electric current.
 Brittle - crystals shatter when struck
with a mallet

EXIT SLIP
Draw the Lewis Dot Diagrams for the Nitrogen
Family.
 Provide and name the ions for Oxygen, Calcium,
and Sulfur.
 What is the chemical formula for Aluminum
Fluoride?


Show the steps you used to determine the formula.