The attraction of opposites

An ionic bond is the attraction of two oppositely charged ions.
These ions combine and the opposite charges cancel each other out like the electrons and protons of an atom.
Combining the ions of different elements creates new matter that is useful to the world today.
For example, when a sodium atom bonds with a chlorine ion, they form sodium chloride which is table salt.

When an atom has less than eight valence electrons it is not chemically stable and must get chemically stable,
It will lose electrons or gain electrons to fill its last energy level and therefore become chemically stable.

Metals will always lose electrons to become chemically stable
Metals will form positive ions
Non metals will always gain electrons to become chemically stable
Nonmetals will always form negative ions

When a sodium atom and a chlorine atom combine, sodium’s one valence electron gets transferred or moved to the chlorine atom.
Both atoms are now ions ;
– sodium is positive and
– chlorine is negative .
– The ions attract each other and bond.
These two form Sodium Chloride , which is table salt.

Sodium’s 1 valence electron is transferred to Chlorine.


Sodium is now stable too
(8 valence electrons).
Chlorine is stable (8 valence electrons).

An ionic bond is the attraction between two oppositely charged ions.
Oppositely charged ions attract each other .
Ionic bonds are formed when electrons are taken and not shared .

The ions attract each other.
Therefore, they bond.

Ionic bonding doesn’t form molecules
The oppositely charged ions are attracted to each other – forming very strong bonds!!

Every ion in an ionic bond is attracted to ions near it that have an opposite charge.
Because of this, all the ions attract many ions.
Therefore, they create a shape.
This shape is 3-D and is called the crystal shape .

Crystal Shape
Ionic solids are generally high melting points
Ionic solids are hard and brittle
Ionic solids conduct electricity only when they are dissolved in water

When ionic compounds are dissolved in water, they conduct electricity .
When they are solid , they don’t conduct .
The ions are tightly bound together and have no room to move or let the electricity flow through.
When dissolved , the ions move more freely; therefore, electricity can flow through them.

Ionic Bonds are very strong .
It takes a lot of heat (energy) to make the particles have enough energy to overcome the attractive forces.
Ionic bonds are so strong that all ionic bonds are solids at room temperature.

Elements Which Form This Bond

Lithium
Sodium
Potassium
Calcium
Magnesium
Aluminum
Oxide
Fluoride
Chloride
Iodide
Sulfide

Writing Chemical formulas for ionic compounds.
• Example:
• Mg
2 valence electrons
Br
7 valence electrons
The point of ionic bonding is giving the electron so that Br can become chemically stable, for it to become chemically stable, the valence electron has to be 8.
The reason you have to double the Br is because you cant have more than 8 valence electrons in one element
Br
The Chemical formula for this compound is MgBr2.
This translates to one magnesium and two
Bromide.

Covalent Bond
Ionic Bond

A Polyatomic ion is an electrically charged collection of more than one atom. Polyatomic ions usually have a charge because the collection of atoms has either gained or lost an electron .
Each polyatomic ion has an overall positive or negative charge . If a polyatomic ion combines with an ion of an opposite charge, an ionic compound forms.

Carbonate ion (CO
3
2-
), made of 1 carbon atom & 3 oxygen atoms.
Combines with Calcium ion (Ca 2+ ).
Makes Calcium Carbonate (CaCO
3
)

What properties do ionic compounds have?
Why are ions in ionic compounds attracted to each other?
What are polyatomic ions?
What is the process of Ionic Bonding?
Summary: What is an Ionic Bond?

Covalent Bond :
– a bond formed by the sharing of electrons between atoms. (does NOT form charges)
– Made up of nonmetals
Molecule : a neutral group of atoms joined together by covalent bonds. (Compounds formed with ionic bonds do NOT have molecules)
Molecular Formula : chemical formula for a molecular compound. It shows how many atoms of each element a molecule contains.

Examples: ascorbic acid (vitamin C): C
6
6 8 6
H
8
O
6 trinitrotoluene (TNT): C
7
H
5
N
3
O
6

Prefix System (binary compounds)
1. Less electronegative atom comes first.
2.
Add prefixes to indicate # of atoms .
Omit mono- prefix on first element.
3. Change the ending of the second element to -ide .
most

PREFIX monoditritetrapentahexaheptaoctanonadeca-
NUMBER
1
2
3
6
7
4
5
8
9
10

Naming Covalent Binary Compounds
P
2
O
CO
5
2
=
=
CO =
N
2
O = diphosphorus pentoxide carbon dioxide carbon monoxide dinitrogen monoxide phosphorous pentachloride = dinitrogen tetrahydride = dichlorine heptaoxide = iodine dioxide =
PCl
5
N
2
H
4
Cl
2
O
7
IO
2

Electron Dot Diagrams
– show valence e as dots
– distribute dots like arrows in an orbital diagram
– EX: oxygen
X
O

Octet Rule
– Most atoms form bonds in order to obtain
8 valence e -
– Full energy level stability ~ Noble Gases
Ne

• Diatomic Molecule: a molecule consisting of two atoms.
• Diatomic molecules in nature:
H
2
, N
2
, O
2
, F
2
, Cl
2
, Br
2
, I
2

Cl Cl
Double Bond: 4 eshared
Single Bond: 2 eshared
O O
N N
Triple Bond : 6 e- shared

Chlorine has 7 valence e -
-1
O
Each oxygen has 6 valence e -
When ClO
3 comes together they form 3 single covalent bonds Cl O
O
One additional electron completes chlorine with a full valence shell, making this a covalently bonded group with an ionic charge of -1

Polarity

Most bonds are a blend of ionic and covalent characteristics.
Difference in electronegativity determines bond type.
E difference: >1.7
E difference: 0.4-
1.7
E difference: 0.0-
0.4

Electronegativity
– Attraction an atom has for a shared pair of electrons.
– higher e neg atom
 
-
– lower e neg atom
 
+

Electronegativity Trend
–Increases up and to the right.

Nonpolar Covalent Bond
–e are shared equally
–symmetrical e density
–usually identical atoms

Polar Covalent Bond
–e are shared unequally
–asymmetrical e density
–results in partial charges (dipole)

+

-

• Nonpolar
– e shared equally
E difference: 0.0-0.4
• Polar
– e shared unequally
E difference: 0.4-1.7
E difference: >1.7
• Ionic
– e transferred

Nonpolar Covalent – equally shared e -
Polar Covalent - partial charges, e shared unequally 
+

-

+

One end of the molecule is slightly negative and the other end is slightly positive
Caused by the presence of a polar bond in the molecule. (structure is not symmetrical)
A molecule that has two poles is called a dipolar molecule, or dipole .
H F

+


Is CO
2 a covalent or ionic compound?
What is CO
2
’s name?
What is the electronegativity difference between C and O?
Does CO
2
Is CO
2 have polar bonds?
a polar molecule overall?
:
. .
O C
. .
O :

Octet achieved by:
Made of:
Ionic
Transfer of electrons
(forming + & - ions)
Covalent
Sharing electrons
Metal cation (+) & Nonmetal anion (-)
Nonmetals (above metalloid line) (no charges)
Characteristics:
Structure:
Representative
Particle:
Brittle
Arranged in alternating
+ & - ions (crystal lattice)
Formula Unit:
(lowest whole number ratio of atoms)
Soft and Squishy
Individual molecules
Molecule:
(group of joined atoms)

Physical State:
Ionic Covalent
Solid Solid, Liquid, Gas
Melting Point:
Electrical
Conductivity:
High
Yes, when dissolved in water or melted
Low
No

1.
Quiz - answer the following on a sheet of paper
The following ball-and-stick molecular model is a representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple (red = O, gray = C, blue = N, ivory =
H):
(a) What is the molecular formula of thalidomide?

2. Above is a ball-and-stick molecular model representation of acetaminophen, the active ingredient in such over-the-counter headache remedies as Tylenol (red = O, gray = C, blue = N, ivory = H):
(a) What is the molecular formula of acetaminophen?