Download unit 4 * organization of matter

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THE ATOM
THE ELEMENTS
THE MOLECULE
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The atom is the fundamental building block
of all things
The matter particles are made from 90
elements found in nature , like all the words
in our language that are formed from the 26
letters of the alphabet
The atoms are like letters of the alphabet :
they allow to form any substances which exist
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The atoms can combine in various ways to
form molecules.
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All such words are combination of letters ,
the molecules are combinations of atoms
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The atoms are comparable to letters The
molecules are comparable to words
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The material is made of particles.
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Scientists have discovered that these
particles are molecules
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These molecules are formed from
combinations of elements
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Atom : The smallest particle in which the
material may be divided The word atom
comes from the Greek atomos , meaning
indivisible
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Molecule : a combination of at least two
atoms which are linked by chemical bonds
Atomic theory :
1) All matter is composed of particles called atoms
2) The atoms themselves are composed of even smaller
particles : protons , neutrons and electrons
 3) The atoms are distinguished from each other by the
quantity of protons , neutrons and electrons which compose
them
 4) The set of atoms that have the same number of protons is
named an element
 5) Atoms combine to form molecules
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The atom is formed by a core of proton and
neutrons ( positive & neutral ) surrounded by
electrons ( negative )
The Electron move around
the core in orbits, which are
more like clouds like planets
orbit around the Sun.
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In the nucleus :
 Protons : Small particles of positive charge
Neutron : Small particles without a charge
(neutral) which may serve as cement between
protons
 In orbit :
 Electrons : Small negatively
charged particles
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Element : The set of atoms that have the
same number of protons
The number of protons is
a characteristic property of
the elements
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Ex Hydrogen has one proton.
- It is the lightest element
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For each item to be neutral , the number of
electrons equals the number of protons
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For an atom without a charge
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Atomic number = Number of protons = Number of electrons
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Ivanovich Mendeleiev , a chemist born in
Siberia, begin to classify items in 1869.
When he placed the items in ascending order
by atomic number , Mendeleiev noticed that
some properties were returning
regularly.
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The periodic table contains all natural and
artificial elements that we know today.
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These elements form the whole visible and
invisible matter that surrounds us.
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In the periodic table , the elements are
classified according to a horizontal axis and a
vertical axis
The horizontal axis : The elements are placed
in order of increasing atomic number
The atomic number is the number of protons
Ex. 1: Hydrogen ( 1 proton )
Ex. 2: Helium ( 2 protons )
Each table row is called A PERIOD
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Vertical axis : The elements are placed according
to the properties they have in common
Each column of the table is called a family or A
GROUP
Ex Column 1 (Alkali metals). The elements form
compounds with all elements.
Ex Column 18 ( the noble gases ) . The elements
rarely form compounds with elements of other
groups
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Scientists use a universal name for one
element : its chemical symbol
The name of an element
can be called differently
country to country , but
the symbol is the same
everywhere
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Each element of the periodic table has its
own symbol
For some items , the symbol is the first letter
of their name in uppercase
For others, the symbol is the first letter of
their name in capital letters followed by a
second letter lowercase
Sometimes we use up to three letters to
describe an item
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The names of the members have diverse
backgrounds
Some come from Latin, ancient Greek or
other languages
Other elements are named after a scientist or
their country of origin
Ex . Einsteinium (Es) , Europium ( Eu) , etc.
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In nature, the atoms are rarely found in the
form of individual atoms. Most of the time ,
the atoms are assembled with one or more
other atoms of the same element or other
elements.
Ex. In nature, hydrogen and oxygen are often
found in molecules ( H2 and O2 ) - Two atoms
of each element bonded together
Ex . Carbon often exists as CO or CO2
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When two or more atoms join together , they
form a molecule.
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In turn , the molecules assemble into all
visible and invisible objects (like the air we
breathe)
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Examples:
DIOXYGEN
CARBON MONOXIDE
CARBON DIOXIDE
NITROGEN OXIDE
WATER VAPOUR
SULPHUR
DIOXIDE
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Examples –
MOLECULE
CHEMICAL
FORMULA
MOLECULAR
MODEL
ATOMIC
COMPOSITION
SAND
1 ATOM SILICON
2 ATOMS OXYGEN
GLUCOSE
6 ATOMS CARBON
12 ATOMS HYDROGEN
6 ATOMS OXYGEN
SODIUM
CHLORIDE
1 ATOM SODIUM
1 ATOM CHLORINE
VINEGAR
2 ATOMS CARBON
4 ATOMS HYDROGEN
2 ATOMS OXYGEN
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Molecules also are represented by the
chemical symbols.
A chemical formula is used to represent the
molecules and indicate the elements that are
part
It contains the symbols of the elements and
the number of atoms being part of the
molecule
Ex . Water: H2O
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Example –
HYDROGEN
SYMBOL
THE NUMBER 2
INDICATES THE
NUMBER OF
ATOMS OF
HYDROGEN
OXYGEN
SYMBOL
THE ABSENCE OF
A NUMBER
INDICATES THAT
ONLY 1 ATOM
OF OXYGEN
IS PRESENT
CHEMICAL FORMULA OF WATER