The attraction of opposites

What Is an Ionic Bond?

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.

Electron Transfer

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.

Ionic Bonding

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

Example Of An Ionic Bond

When a sodium atom and a chlorine atom combine, sodium’s one valence electron gets

transferred

atom. or moved to the chlorine 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.

Diagram: Na + Cl

Sodium’s

1 valence

electron is

transferred

to Chlorine.

Result: Na + Cl



NaCl

Sodium is now

stable

(8 valence electrons).

too Chlorine is stable (8

valence electrons).

Forming Ionic Bonds Things to remember!

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

.

Pictures of Forming Ionic Bonds

The ions attract each other. Therefore, they bond.

Ionic bonding forms compounds

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

Crystal Shape

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

.

Characteristic of ionic bonds:

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

Electrical Conductivity

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.

High Melting Points

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

Metal + Nonmetal = Ionic Bond

Common Ions 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.

Pictures Of Atomic Bonds Covalent Bond Ionic Bond

Polyatomic Ions

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.

Example of A Polyatomic Ion

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

Did You Understand?

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 Bonding

Covalent Bonding

Covalent Bond :

– a bond formed by the

sharing of electrons

between atoms. (does NOT form charges) – Made up of

nonmetals Molecule :

molecules) a neutral group of atoms joined together by covalent bonds. (Compounds formed with ionic bonds do NOT have

Molecular Formula :

chemical formula for a molecular compound. It shows how many atoms of each element a molecule contains.

Covalent Bonding

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

Molecular Nomenclature

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 element to -ide .

of the second most

Molecular Nomenclature

PREFIX

mono di tri tetra penta hexa hepta octa nona deca-

NUMBER

1 2 3 4 5 6 7 8 9 10

Naming Covalent Binary Compounds

P 2 O 5 CO 2 = = CO = N 2 O = di phosphorus pent oxide carbon di oxide carbon mon oxide di nitrogen mon oxide phosphorous penta chloride = di nitrogen di tetra chlorine hepta iodine hydride = di oxide = oxide = PCl 5 N 2 H 4 Cl 2 O 7 IO 2

Lewis Structures

Electron Dot Diagrams

– show valence e

as dots

– distribute dots like arrows

in an orbital diagram

– 4 sides = 1 s-orbital, 3 p-orbitals – EX: oxygen X

O

2s 2p

Lewis Structures

Octet Rule

– Most atoms form bonds in order to obtain

8 valence e -

– Full energy level stability ~ Noble Gases

Ne

Diatomic Molecules

• •

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 “Professor BrINClHOF”

#s of Covalent Bonds

Cl Cl

Double Bond: 4 e shared Single Bond: 2 e shared

O O N N

Triple Bond: 6 e- shared

Polyatomic Ions and covalent bonding “CHLORATE”

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

Polyatomic Ions and covalent bonding “CARBONATE”

Carbon has 4 valence e Each oxygen has 6 valence e-

O

2 When CO 3 form comes together they 2 single covalent bonds and 1 double covalent bond

C O O

Two additional electrons completes carbon with a full valence shell, making this a covalently bonded group with an ionic charge of -2

Polyatomic Ions and covalent bonding “PHOSPHATE”

O

Phosphorus has valence e 5 3 -

O P O

When PO 4 comes together they form 3 single covalent bonds

O

Three additional electrons completes phosphorus with a full valence shell, making this a covalently bonded group with an ionic charge of -3

Polarity

Bond 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

Bond Polarity

Electronegativity

–

Attraction an atom has for a shared pair of electrons.

–

higher e neg atom

 

-

–

lower e neg atom

 

+

Bond Polarity

Electronegativity Trend

–Increases up and to the right.

Table of Electronegativity

Bond Polarity

Nonpolar Covalent Bond

–e are shared equally –symmetrical e density –usually identical atoms

Bond Polarity

Polar Covalent Bond

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

•

Nonpolar

–

e shared equally

Bond Polarity

E difference: 0.0-0.4

•

Polar

–

e shared unequally

E difference: 0.4-1.7

E difference: >1.7

•

Ionic

–

e transferred

Bond Polarity

Nonpolar Covalent

– equally shared e -

Polar Covalent

- partial charges, e unequally 

+

shared 

-



+

Polar Molecule

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  + 

Self Test

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 :

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?