the ancient greeks used to believe that everything was made up of very small particles. i did some...
TRANSCRIPT
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