1. THE ATOM THE ELEMENTS THE MOLECULE

2.  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

3.  The atoms can combine in various ways to form molecules.  All such words are combination of letters, the molecules are combinations of atoms  The atoms are comparable to letters The molecules are comparable to words

4.  The material is made of particles.  Scientists have discovered that these particles are molecules  These molecules are formed from combinations of elements

5.  Atom : The smallest particle in which the material may be divided The word atom comes from the Greek atomos, meaning indivisible  Molecule : a combination of at least two atoms which are linked by chemical bonds

6.  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

7.  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.

8.  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

9.  Element : The set of atoms that have the same number of protons  The number of protons is a characteristic property of the elements  Ex Hydrogen has one proton. - It is the lightest element

10.  For each item to be neutral, the number of electrons equals the number of protons  For an atom without a charge  Atomic number = Number of protons = Number of electrons

11.  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.

12.  The periodic table contains all natural and artificial elements that we know today.  These elements form the whole visible and invisible matter that surrounds us.

14.  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

15.  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

16.  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

17.  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

18.  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.

19.  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

20.  When two or more atoms join together, they form a molecule.  In turn, the molecules assemble into all visible and invisible objects (like the air we breathe)

21.  Examples: DIOXYGEN CARBON DIOXIDE WATER VAPOUR CARBON MONOXIDENITROGEN OXIDESULPHUR DIOXIDE

22.  Examples – SAND GLUCOSE SODIUM CHLORIDE VINEGAR MOLECULE CHEMICAL FORMULA MOLECULAR MODEL ATOMIC COMPOSITION 1 ATOM SILICON 2 ATOMS OXYGEN 6 ATOMS CARBON 12 ATOMS HYDROGEN 6 ATOMS OXYGEN 1 ATOM SODIUM 1 ATOM CHLORINE 2 ATOMS CARBON 4 ATOMS HYDROGEN 2 ATOMS OXYGEN

23.  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

24.  Example – HYDROGEN SYMBOL OXYGEN SYMBOL THE NUMBER 2 INDICATES THE NUMBER OF ATOMS OF HYDROGEN THE ABSENCE OF A NUMBER INDICATES THAT ONLY 1 ATOM OF OXYGEN IS PRESENT CHEMICAL FORMULA OF WATER