An atom is the smallest stable unit of matter
An element is a pure substance made of only one type of atom.
There are about 120 elements , so 120 different atoms exist.
In the periodic table the elements are organized in rows.
The vertical columns are called groups
The horizontal rows are called periods.
Li, Na and k are in the same group
N , O , F are in the same period.
If the elements are in the same group they have the same number of electrons in the outer shell.
This elements in their same groups can have similar chemical and physical properties.
Some groups have specific names :
Group 1 elements : are named ALKALI
Group 2 elements : ALKALI EARTH METALS
Group 7 elements : HALOGEN
Group 0 elements : NOBLE GASES
Group 1 - ALKALI metals
Lithium - atomic number 3 :(2,1)
Sodium- atomic number 11 : (2,8,1)
Potassium - atomic number 19 : (2,8,8,1)
METALS AND NON-METALS
Fluorine : sodium fluoride
chlorine : pool , cleaning products
bromine : some medicine , fire resistant plastic
Iodine : test for starch iodoform , added to table salt.
Astatine : highly radioactive and unstable
NORMAL PROPERTIES OF TRANSITION METALS
Shared with group 1
Grey in colour (usually)
May be essential minerals diet
Good conductors heat + electricity
Not Shared with group 1
High melting points
Harder + stronger
Catalysts - elements or compounds
elements in group 7
First 5 elements:
Fluorine atomic number 9 : 2,7
Chlorine atomic number 17 : 2,8,7
STRUCTURE OF AN ATOM
1/2000 or 0
The electrons are arranged in orbits called shells
First shell holds up to 2.
Second shell holds up to 8.
Third shell can hold up to 8 .
Then you continue up to the fourth shell.