Bonding

Electron Configuration

• Remember that electron configuration refers to the arrangement of electrons in the orbital of an atom!

Three Types

We will study . . .Ionic Bonding

Covalent Bonding

Metallic Bonding

occurs between a metal and a nonmetal

occurs between two nonmetals

occurs WITHIN a metal sample

Ionic and Covalent Bonding Video Clip

• http://www.youtube.com/watch?v=QqjcCvzWwww

Chemical Bonding

• Compounds are formed from chemically bound atoms or ions.

• Bonding involves only the valence electrons.

• When atoms combine we call them molecules.

Valence Electrons• Electrons are found in specific

orbits/clouds spinning around the nucleus

• Valence electrons are the electrons located in the outermost orbit

Elements become stable when:

their outer orbit contains 8 electrons or their outer orbit becomes empty

Lewis Dot Diagrams show the # of Valence Electrons

Why are the noble gases unreactive?

The Octet RuleWhen the highest energy level of an atom is filled, the atom is stable.Atoms tend to gain, lose, or share electrons until they have eight valence electrons.Hydrogen and Helium are the only exceptions. Because they are so small, they are satisfied with two valence electrons.

Complete this chart:

Lewis Symbols / Electron Dot Diagram

Lewis symbols show the valence electrons as dots arranged around the atomic symbol.

hydrogen:

sodium:

chlorine:

Na

H

Cl

Dot Diagrams• Show the number of valence

electrons Lewis Dot Diagrams of Selected Elements

                                                                                                                      

                                

An oxidation number indicates how many electrons are lost or gained during the bonding process.

•Mg loses 2 electrons so it has an oxidation number of +2

•Oxygen gains 2 electrons

so it has an oxidation

number of –2.

Oxidation #

The periodic table show the common oxidation numbers for groups on the periodic

table.

Ionic Bonds – formed when atoms gain or lose electrons.

Ex: Na has 1 valence e-

=

When Na loses that electron, its 2nd E.L. becomes full andstable with 8 e-.

Atoms with an electrical

charge are called ions.

Ionization•When an atom loses or gains electrons they become ions – or atoms with an electrical charge.

•If an atom LOSES an electron, it becomes an ion with a +1 charge.

•If an atom GAINS an electron, it becomes an ion with a –1 charge.

Chlorine has 7 valence electrons.

If Cl gains 1 electron, its valence shell will be full and stable.

Opposites attract, so…

Ionic Bonds

• form between a metal and a nonmetal• form as a result of a transfer of electrons

• Na becomes a positive ion =• Cl becomes a negative ion =• Cation means “to go down”

– also think cast off

• Anion means “to go up”– Also think accept

Na Cl

CationAnion

Ions Ions 1. Positively or negatively charged atoms. 2. (Number of protons not equal to the number of electrons.)3. Metals – give up electrons to form positive ions. (example: )4. Nonmetals – take in electrons to form negative ions. (example: )

Ionic Bonds

What is the formula for the compound that forms between magnesium and chlorine?

Cl

Mg

Cl

Ionic CompoundsIonic compounds consist of a lattice of

positive and negative ions.

Ionic Compounds,Characteristic Properties

• High melting points• High boiling points

• Conduct electric current when melted and when dissolved in solution

• All of these properties are a result of the strong attraction among ions within the crystal lattice

Animated Reactionsodium and chlorine

• http://www.visionlearning.com/library/module_viewer.php?mid=55

• Youtube video of sodium reacting with chlorine

Covalent Bonds

• form between two nonmetal atoms• form as a result of a sharing of

electrons

Covalent Bonding

Most atoms share electrons to gain an octet.

Covalent bonds are formed when e- are shared.

– covalently bonded atoms of the same type.

Exs: H2 Cl2 F2

I2 O2

Br2 N2

Diatomic molecules:

Polar Molecules• The type of atoms and

their shape determine if a molecule is polar or not

• With polar molecules there is an uneven distribution of charge…one atom has a stronger attraction for the electrons than the other

• Polar molecules attractions are stronger than nonpolar molecules

Polar Covalent Bonding

in a water molecule

• http://www.visionlearning.com/library/module_viewer.php?mid=55

Molecular Compounds,Characteristic Properties

• Low melting points• Low boiling points• Usually gases or liquids at room

temp.• Does not conduct electricity well• May or may not dissolve in water

(there are several types of molecular compounds)

Note the correct name

for a compound that

contains covalent bonds

In GENERAL:

•Ionic Bonds– metal / nonmetal

•Covalent Bonds– 2 nonmetals

Double Bubble – Compare/Contrast Ionic and

Covalent Bonding

Double Bubble – Compare/Contrast Ionic and Covalent Bonding