The Ancient Greeks used to believe that everything was made up of very small

particles. I did some experiments in 1808 that proved this and called these particles

ATOMS:

Dalton

Elements are substances that consist of just one type of atom- they cannot be brokendown to other substances

The basic unit of all matter is the atom, the smallest unit of matter that retains the properties of an element

A Molecule is a substance containing 2 or more atoms

A Compound is a substance containing 2 or more elements

Is brass an element? What about: Oxygen O2

Water H20 Helium He

Is brass a molecule?

Is brass a compound?

The structure of the atom

ELECTRON – negative,

orbits outside the nucleusPROTON –

positive, also in nucleus

NEUTRON – neutral, located in

the NUCLEUS (center of atom)

The Atom Hydrogen

Proton Electron

Hydrogen has one proton, one electron and NO neutrons

The Atom Helium

ElectronProton

Neutron

Helium has two electrons, two protons and two neutrons

The Atom Carbon

Protons

Neutrons

Electrons

Carbon has six electrons, six protons and six neutrons.

The Atom Nitrogen

Protons

Neutrons

Electrons

Nitrogen has seven electrons, seven protons and seven neutrons.

The Atom Oxygen

Protons

Neutrons

Electrons

Oxygen has eight electrons, eight protons and eight neutrons.

red and green are opposites

assume red and green cancel each other

net color = neutral

take away one red

take away one red net color = 1 green

take away two red

take away two red net color = 2 green

net color = neutral

net color = 2 red

in this arrangement…

green is trapped inside.Only red ballscan be added ortaken away…

color = 2 green

color = 1 red

color = ?

3 red

color = ?

3 green

+

the positive (+) particle is called a

proton

the negative (-) particle is called an

electron

++

++

+

positive and negative are opposites

they cancel each other out

++

++

+

net charge = zero

++

++

+

in an atom,protons ( ) are inthe centerand electrons ( )are on the outside

+

++

++

+

only electrons ( )can be addedor taken away

++

++

+

this is an atom with5 electrons and

5 protons

++

++

+

the atom is neutral

net charge = zero

++

++

+

5 (-) and 5 (+) = zero charge (neutral)

++

++

+

charge = ?

++

++

+

charge = 1- (one minus)

++

++

charge = ?

++

++

+

2+ (two plus)

WHEN REMOVING ELECTRONS

WHEN REMOVING ELECTRONS

THE RESULTING CHARGE IS POSITIVE

WHEN REMOVING ELECTRONS

THE RESULTING CHARGE IS POSITIVE

neutral 1+

WHEN ADDING ELECTRONS

THE RESULTING CHARGE IS NEGATIVE

WHEN ADDING ELECTRONS

THE RESULTING CHARGE IS NEGATIVE

neutral 2

WHEN ADDING ELECTRONS

An atom with positive or negative charge

is called andrum roll

ION

Hydrogen atoms are very reactive….Helium is not. Which do you think the Hindenburg was filled with?

Atoms want 8 electrons in the outermost shell. If atoms have less than 8 then they react with other atoms to gain or lose electrons.

IonicBonds

Reacting with other atom can cause atoms to bond with each other. In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS

in ionic compounds.

FK

FK+ _

The compound potassium fluorideconsists of potassium (K+) ions

and fluoride (F-) ions

FK+ _

The ionic bond is the attractionbetween the positive K+ ion

and the negative F- ion

CovalentBonds

But rather than losing or gainingelectrons,atoms now share an electron pair.

In covalent bonding,atoms still want 8 electron in the outer shell

Cl2

Chlorineforms

acovalent

bondwithitself

ClClHowwilltwochlorineatomsreact?

ClClEach chlorine atom wants to gain one electron to achieve get 8

Cl Cl8

Cl Cl

circle the electrons foreach atom that completestheir octets

8

Cl Cl

circle the electrons foreach atom that completestheir octets

Each atom has 8 electrons byeach atom sharing theelectron pair in the middle

Cl Cl

circle the electrons foreach atom that completestheir octets

It is called a SINGLE BOND

Cl Cl

circle the electrons foreach atom that completestheir octets

Single bonds are abbreviatedwith a dash

O2

Oxygen

How will two oxygen atoms bond?

OO

OOEach atom has two unpaired electrons

Both oxygen atoms want to gain two electrons.

OO

8

OO

8

OO

two set of shared electrons,

OOmaking a double bond

OO=For convenience, the double bond

can be shown as two dashes.

OO

OO=This is the oxygen molecule,

O2

this is so

cool!!

Covalent bonding allows for an amazingly large variety

of compounds such as

small compounds likewater and carbon dioxide,

and alcohol (ethanol),

to larger compoundssuch as aspirin,

(21 atoms)

to all of the 40,000 different proteinsyou have in your body,

including

insulin,with about 900 atoms,

and hemoglobin,with about 11,000 atoms!

There are an estimated1040 possible compounds

containing up to 50 atoms

The known chemical world,including natural andsynthetic compounds,

is far far far below 1% of that.

NATURE volume 442 p. 502 3 August 2006