CHEMISTRY BELL RINGER
IAN PG.
Week of 11/16/2015
Tuesday 11/17/15
1.DEFINE VALENCE ELECTRONS.
2.HOW ARE THE NUMBER OF VALENCE
ELECTRONS OF THE REPRESENTATIVE
ELEMENTS DETERMINED?
3.DESCRIBE CATIONS.
4.DESCRIBE ANIONS.
7-1 IONS
IaN pg.
MAIN IDEAS
KEY CONCEPTS
1. Valence
Electrons
2. Electron Dot
Structures
3. Octet Rule
4. Halide Ions
1. How do you find the
number of valence
electrons in an atom of a
representative element?
2. Which atoms tend to gain
electrons? Lose?
3. How are cations formed?
4. How are anions formed?
Small deeds done are better than great deeds planned.
-Peter Marshall
Ionic Bonds
 The behavior of sodium…
 Look at its electron configuration
 Sodium = group IA = 1 valence electron
 Valence electrons are the electrons in the highest
occupied energy level of an element’s atoms.
 Sodium wants to be like a noble gas.
 At most, an atom can only gain or lose 3 electrons.
 Sodium will lose 1 electron.
 Sodium now has the electron configuration of
neon.
 Is it neon? No. It still has 11 protons. It is
isoelectronic with neon.
 Now it looks like this: Na+
 The behavior of chlorine…
 Look at its electron configuration
 Chlorine = group 7A = 7 valence electrons
 Chlorine wants to be like a noble gas.
 At most, an atom can only gain or lose 3
electrons.
 Chlorine will gain 1 electron.
 Chlorine now has the electron configuration
of a noble gas (argon).
 Now it looks like this: Cl-
Ions
 The transfer (or movement) of electrons
produces ions.
 Cations (Cat-ions) = ions with a positive
charge.
 Anions = ions with a negative charge.
 Anions will usually end in –ide when naming them.
Opposites Attract
 An ionic bond is a chemical bond that is
formed from the attraction between a cation
and an anion. This is an electrostatic
attraction.
 Ionic bonds form compounds that are usually
called salts.
 Salts typically have crystalline structures.
 Octet Rule – in forming compounds, atoms
tend to achieve the electron configurations of
noble gases.
 Metals tend to lose electrons to achieve this.
 Nonmetals tend to gain electrons to achieve this.
 Some ions formed by transition metals do not have
noble gas configurations and are exceptions to the
octet rule – more on this later.
 The electrical charge that an atom achieves (in
trying to become more like a noble gas) is
sometimes called its oxidation state.
CHEMISTRY BELL RINGER
IAN PG. 26
Week of 11/16/2015
Wednesday 11/18/15
IONIC BONDING & LEWIS DOT DIAGRAMS
Putting Ions Together –
Ionic Compounds
 Ionic compounds must be neutral, which
means the positive charge of the cation and
the negative charge of the anion must
balance each other.
 Ex. NaCl = Na+ and Cl- = a balanced charge.
 What if Mg and Br form a compound?
 We want to know the formula unit. The formula unit
is the lowest, whole number ratio of ions in an ionic
compound.
 1. Write the elements side by side with the metal on
the left:
Mg
Br
 2. Decide how to balance their charges:
Mg2+
Br1 3. Rewrite:
MgBr2
 How about Al and O?
 1. Write the elements side by side with the metal
on the left:
Al
O
 2. Decide how to balance their charges:
Al3+
O2 3. Rewrite:
Al2O3
 Compounds made with polyatomic ions work
the same way…
 Combine NH4 with S:
 1. Write the elements side by side:
NH4
S
 2. Decide how to balance their charges:
NH41+
S2 3. Rewrite:
(NH4)2S
 Notice that the polyatomic needs to be in
parenthesis before adding the subscript.
V. Lewis Dot Structures
A. “Dot Models” used to
represent Valence electrons
B. Gilbert Newton Lewis 1875-1946
American Chemist
discovered covalent bond
Groups Review
Group 1 = 1 electron
Group 2 = 2 electrons
Group 8 = 8 electrons
Except for He, it has 2
electrons
•Each column is
called a “group”
•Each element in a
group has the same
number of electrons
in their outer energy
level.
•The electrons in the
outer energy levels
are called “valence
electrons”
C. Drawing Lewis Dot
Structures
1. Write the element symbol.
2. Locate the group (1 – 8) This is the
# of valence electrons.
3. Follow this diagram for placing
“Dots” in order.
Copy this down
Assignment…
 Practice problems # 1 & #2 pg. 193
 Section Assessment #3-11 pg. 193