Essential Questions:
What are the processes by which different
atoms come together to form new compounds
and what forces hold solutions of these
compounds/molecules together?

An atom with a charge
 Positive: cation
 Negative: anion
How do these atoms become charged?


Electrons in the highest occupied energy level
The number of valence electrons greatly
determines chemical properties of an
element and how it will react
How can we find the number of valence
electrons in an element?
Electron configuration for chlorine:
1s22s22p63s23p5
What is the highest energy level reached? 3
How many electrons are there? 7
Looking at the electron configuration for
elements in the same group, they will all have
the same number of valence electrons (just
the A groups though! Not the B groups.)
How many valence electrons are there in the
following elements?
Chlorine
Calcium
Aluminum
Carbon
Neon


1.
2.
3.
Also known as Lewis Structures
Diagrams that represent the number of
valence electrons in the atom
Find number of valence electrons
Write element symbol
Fill valence electrons around symbol, one on
each side first then double up
Find the Lewis Dot Structures for the following
elements:
Chlorine
Calcium
Aluminum
Carbon
Neon


Noble gases are the most stable elements on
the Periodic Table due to the fact that they
have 8 valence electrons (a complete outer
shell)
Atoms will either lose or gain electrons
through bonding in order to attain those
complete 8 configurations
 Metal elements tend to lose electrons while
nonmetals tend to gain

How do cations form?
 Losing valence electrons
▪ Who tends to form cations?

How do anions form?
 Gaining valence electrons
▪ Who tends to form anions?


Metals
Lose valence electrons
Example: Calcium
Normal calcium
calcium ion
20 protons
20 electrons
no charge
20 protons
18 electrons
+2 charge


Nonmetals
Gain electrons to get to an octet
Example: Chlorine
normal chlorine
chlorine ion
17 protons
17 electrons
no charge
17 protons
18 electrons
-1 charge




Composed of a cation and an anion
Held together by ionic bonds
Represented by a chemical formula
A formula unit is the lowest whole-number
ratio of ions in an ionic compound

When writing the formulas, use the crisscross method
Mg+2
Cl-1
MgCl2

For the following pairs of elements, write the
formula for the ionic compound formed
Aluminum and Chlorine
Sodium and Sulfur
Nitrogen and fluorine