Presentation on theme: "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."— Presentation 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 broken down 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 O 2 Water H 2 0 Helium He Is brass a molecule? Is brass a compound?
The structure of the atom ELECTRON – negative, orbits outside the nucleus PROTON – 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 Electron Proton 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
net color = 1 green
take away two red
net color = 2 green
net color = neutral
net color = 2 red
in this arrangement …
green is trapped inside. Only red balls can be added or taken away…
color = 2 green
color = 1 red
color = ?
color = ?
+ 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 in the center and electrons ( ) are on the outside +
+++++ only electrons ( ) can be added or taken away
+++++ this is an atom with 5 electrons and 5 protons
+++++ the atom is neutral net charge = zero
(-) and 5 (+) = zero charge (neutral)
+++++ charge = ?
+++++ charge = 1- (one minus)
++++ charge = ?
( two plus )
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 an drum 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.
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 fluoride consists of potassium (K + ) ions and fluoride (F - ) ions
FK + _ The ionic bond is the attraction between the positive K + ion and the negative F - ion
But rather than losing or gaining electrons, atoms now share an electron pair. In covalent bonding, atoms still want 8 electron in the outer shell
Cl 2 Chlorine forms a covalent bond with itself
Cl How will two chlorine atoms react?
Cl Each chlorine atom wants to gain one electron to achieve get 8
circle the electrons for each atom that completes their octets 8
Cl circle the electrons for each atom that completes their octets Each atom has 8 electrons by each atom sharing the electron pair in the middle
Cl circle the electrons for each atom that completes their octets It is called a SINGLE BOND
Cl circle the electrons for each atom that completes their octets Single bonds are abbreviated with a dash
How will two oxygen atoms bond? OO
OO Each atom has two unpaired electrons
Both oxygen atoms want to gain two electrons. OO
8 O O
8 O O
two set of shared electrons, O O making a double bond
O O = For convenience, the double bond can be shown as two dashes. O O
O O = This is the oxygen molecule, O 2 this is so cool! !
Covalent bonding allows for an amazingly large variety of compounds such as
small compounds like water and carbon dioxide,
and alcohol (ethanol),
to larger compounds such as aspirin, (21 atoms)
to all of the 40,000 different proteins you have in your body, including
insulin, with about 900 atoms,
and hemoglobin, with about 11,000 atoms!
There are an estimated possible compounds containing up to 50 atoms The known chemical world, including natural and synthetic compounds, is far far far below 1% of that. N ATURE volume 442 p August 2006