ThursdayOctober 25, 2012

(Orbital Notation; Introduction to

Chemical Bonding)

Determine which elements are represented by each of the following

notations:1s2, 2s2, 2p3

Uranium-238 nitrogen1s2, 2s2, 2p6,

3s2, 3p6, 4s2calcium1s2, 2s2, 2p5fluor

inecarbon-12

1s 2s 2px 2py 2pz 3s 3px 3py 3pzchlorine

Bell RingerThursday, 10-25-12

Bell Ringer Thursday, 10-25-12

Use Lewis Dot Structures to

show how water is formed.

Do the same for table salt, NaCl.

Announcements

Assignment Currently Open

Summative or Formative? Date Issued Date Due Date Into

GradeSpeed Final Day

QUIZ 6 S3 10/5 10/5 10/26QUIZ 7 S4 10/12 10/12 10/26

Pop Quiz – The Periodic Table and the Periodic Law

F4 10/16 10/16

QUIZ 8 S5 10/19 10/19 10/22 11/2WS – Valence Electrons and

Electron Configuration

F5 10/22 10/26 10/26

WS – Average Atomic Mass F6 10/22 10/26 10/26

WS – Electron Dot Notation F7 10/23 10/26 10/26

WS – Arrangement of Electrons in

AtomsF8 10/24 10/26 10/26

Example : Neon10 protons, 10 neutrons, 10 electrons

1s2, 2s2, 2p6

Our fourth notation, Orbital Notation, is based upon the fact that electrons settle into pairs in what’s called an

“orbital.”Think of an orbital as a shoebox and the two electrons in

the orbital as shoes.In this notation, electrons are represented as arrows and

p sub-levels are divided into three orbitals holding 2 electrons each.

1s 2s 2px 2py 2pz

Chemical Bonding

Chemical BondingAtoms seldom exist as

independent particles in nature.

A chemical bond is a mutual electrical

attraction between the nuclei and valence

electrons of different atoms that binds the

atoms together.

Chemical BondingWhy are most atoms chemically bonded to each other? – as

independent particles, they are at relatively high potential energy.Nature, however,

favors arrangements in which potential

energy is minimized.

Chemical BondingThis means that

most atoms are less stable existing by themselves than when they are

combined.By bonding with

each other, atoms decrease in potential

energy, thereby creating more stable

arrangements of matter.

Types of Chemical BondsChemical bonds are formed to stabilize

atoms by reducing the single atoms’ potential

energy.When atoms bond, their

valence electrons are redistributed in ways that make the atoms

more stable.The way in which the

electrons are redistributed determines

the type of bonding.

Types of Chemical BondsMain block (s and p) metals (and H) tend to lose electrons to form

+ ions (cations), while non-metals tend to gain electrons to form –

ions (anions).

Chemical bonding that results from the attraction between large numbers of cations and anions is called

ionic bonding.

When atoms either lose or gain electrons in order to bond, it is referred to as a transfer of electrons.

In order to bond, these atoms lose electrons and

form + cationsIn order to bond, these

atoms gain electrons and form - anions

Ionic Bonding

Atom A represents a

metal element that has lost electrons to

form + cations.

Atom B represents a

non-metal element that has gained electrons to

form - anions.

The result is a cluster of ions of both types that are stuck together because of

their opposite electromagnetic charges.

Types of Chemical Bonds

Chemical bonding that results from the sharing of electron pairs between two

atoms is called covalent bonding.

The non-metal and metalloid elements

indicated here share electrons when they bond

with each other.

When two or more non-metals or metalloids bond, atoms don’t lose or gain

electrons; rather they share pairs of valence

electrons.

Covalent Bonding

Atom C represents a non-metal or

metalloid element.

Atom D represents a different non-

metal or metalloid element.

The result is two atoms held together by the sharing of the pair(s) of valence electrons.

This unit is called a molecule.

Ionic or Covalent?What determines if atoms of different

elements will bond ionically or covalently?The electronegativity difference between the

two bonding elements makes the determination.

Bonding between atoms of different elements is rarely purely ionic or covalent, but falls somewhere between based upon these

electronegativity differences.By calculating the difference in the

electronegativity values of the involved atoms, you can predict the degree to which

the bond is likely to be ionic or covalent.

Example 1: atoms of sodium and chlorine are bonding. Sodium’s electronegativity is 0.9. Chlorine’s is 3.0. If we take the difference we get:

3.0 – 0.9 = 2.1

Consult the Bonding Character Chart and

see where the difference falls.

2.1

This falls in the Ionic range; therefore,

sodium and chlorine will bond ionically.

Example 2: atoms of hydrogen and oxygen are bonding. Hydrogen’s electronegativity is 2.1. Oxygen’s is 3.5. If we take the difference we get:

3.5 – 2.1 = 1.4

Consult the Bonding Character Chart and

see where the difference falls.

1.4This falls in the Polar-covalent

range; therefore, hydrogen and

oxygen will bond covalently.

Example 3: two atoms of nitrogen are bonding. Nitrogen’s electronegativity is 3.0. If we take the difference we get:

3.0 – 3.0 = 0

Consult the Bonding Character Chart and

see where the difference falls.

0

This falls in the Nonpolar-covalent

range; therefore, two atoms of nitrogen

will bond covalently.

Introduction to Chemical Bonding

Worksheet