Lewis Dot Diagrams and
Ions
Valence Electrons
The valence electrons are the electrons in
the outermost shell of the atom
 Consider sodium:
 How many protons?
 How many neutrons?
 How many electrons?
 Draw a Bohr model for sodium

Valence Electrons

Bohr model for sodium:

The electron(s) in the highest shell are
valence electrons
Lewis Dot Diagram

To draw a Lewis Dot Diagram:
Write the element symbol
 Figure out how many valence electrons the
atom has
 Use dots to represent the valence electrons

 Put
them in pairs around the 4 sides of the element
symbol

For example – try sodium
Lewis Structure Practice

Draw a Lewis Structure for:
Calcium
Neon
Silicon
Ions
Ions are atoms that have the same
number of protons, but different numbers
of electrons
 An ion forms when an atom gains or loses
electrons to become more stable
 Which group is the most stable?
 How many valence electrons does that
group have?

Ions
When nonmetals form ions, they tend to
gain electrons to fill their valence shell with
8 electrons
 When metals form ions, they tend to lose
all of their valence electrons

Positive Ion Formation
 Atoms
in Group 1 lose 1 electron to
form ions with a +1 charge
 Atoms in Group 2 lose 2 electrons to
form ions with a +2 charge
 Atoms in Group 13 lose 3 electrons to
form ions with a +3 charge
 Positive ions are called cations
Negative Ion Formation
 Atoms
in Group 17 gain 1 electron to
form ions with a -1 charge
 Atoms in Group 16 gain 2 electrons to
form ions with a -2 charge
 Atoms in Group 15 gain 3 electrons to
form ions with a -3 charge
 Negative ions are called anions
Ionic Compounds
When atoms form ionic compounds, an
atom transfers one or more of its valence
electrons to another atom.
 Consider NaCl
 Na loses 1 electron to become Na+1
 Cl gains 1 electron to become Cl-1
 The transfer of electrons from one atom to
the other causes a more stable
arrangement of electrons.

Ionic Compounds
 May
be made from a metal and a
nonmetal - KI
 May be made from a metal and a
polyatomic ion (Look at your
reference table) – LiOH
 May be made from two polyatomic
ions - NH4C2H3O2
Naming Ionic Compounds
The name of the positive ion stays the
same
 The end of the element name of the
negative ion is changed to an –ide suffix
 Chlorine to chloride
 Sulfur to sulfide
 Phosphorus to phosphide
 Polyatomic ions stay as they are written

Ionic Formulas

What ion does sodium form?


What ion does chlorine form?


Cl-1
What do we change the name of the
negative ion to?


Na+1
Chloride
What is the name of the compound?
Ionic Formulas
What is the formula for the compound
made from sodium and chloride ions?
 What is the compound made from
potassium and iodide ions?

Ionic Formulas Activity
Work in pairs to complete the activity.
 Please put all of the shapes back in the
bags when you are finished.

Rules for Naming Ionic Compounds
 The
first element keeps its name.
 For monatomic ions, the second
element gets the –ide suffix (ending).
 Polyatomic ions always keep their
names whether they are first or
second.
Practice

Name the following ionic compounds:
KF
MgBr2
Li2S
Ca3N2
NaNO3
Mg(OH)2
Exit Ticket
 Draw
a Lewis Structure for
magnesium
 Give the charge on a magnesium ion
 Give the formula for a compound
made from magnesium and bromine
 Give the name for CaCl2