1. Chemistry Notes on The Periodic Table
Syllabus 5070
‘O’ level

2. The Periodic Table:
The elements in the periodic table are classified according to their atomic number(number of protons).There are 8 groups and 7 periods in the periodic table.
The Group:
The group is the vertical column of the periodic table in which elements having similar chemical properties are arranged. The group number represents the valency electrons(number of electrons in the outermost shell).
Example: The elements found in Group I contain I valency electron(1electron in their outermost shell) whereas the elements found in Group vii contain 7 electrons in their outermost shell.
The Period:
the period is the horizontal row in which elements are arranged according to their atomic numbers. In fact, the elements are arranged in an increasing order depending on the proton number. The first 3 periods are short whereas the other 4 periods are long( the 1st period is the shortest one as it contains only 2 elements).

3. The elements in period 2 according to periodic table 7 Li 3 9 Be 4 11
The period number:
The period number represents the number of shells in which elements are placed. Example: The elements found in the 1st period contain only one shell of electron whereas the elements found in the 4th periods contain 4 shells of electrons. Example: For period 2:
The elements in period 2 according to periodic table 7 Li 3 9 Be 4 11 B 5 12 C 6 14 N 16 O 8 19 F 20 Ne 10
Electronic configuration
2,1
2,2
2,3
2,4
2,5
2,6
2,7
2,8

4. Group I elements and its Properties
They are called Group I elements because they all have 1 electron in their outermost shells. They are also known as Alkali metal as they form alkalis when they react with water( e.g: LiOH, NaOH, KOH, RbOH, CsOH, FrOH). Properties: 1)They are soft metals. 2)They allow the conduction of electricity in the solid state(because of the presence of delocalised electrons). 3)They have low densities and hence have low melting point and boiling point. NOTE: There's a decrease in melting point as well as boiling point as we move down the group(Group i). 4) They are reactive metals. As we move down the group, the reactivity of the metals increase. 5)They form alkalis because their oxides(LiOH, NaOH, etc..) which are basic oxides, are soluble in water. Hence, the basic oxides can react with acids to form salt and water( neutralisation reaction). Example: Li O + H O 2LiOH LiOH + 2HCl 2LiCl + H O(It’s a neutralisation reaction ) (Basic Oxide)

5. 6)The Group I metals react with dilute acids to form salts and hydrogen gas. Metal + Acids Salt + Hydrogen Gas Li + HCl 2LiCl + H 2K + 2HNO 2KNO + H 7) Their carbonates(e.g:Na CO )are stable and thus, they do not decompose on heating. That's why those metals carbonates can’t be reduced by CO or C in order to extract them from their ores. As a result, electrolysis is performed in order to extract the pure metals from its carbonates. NOTE: Group I metals carbonates are soluble in water. 8) The Group I elements form ionic compound(electrovalent bonding) with non- metals( e.g:NaCl).

6. Group vii elements and its properties: Group vii elements are known as the family of halogens with 7 electrons in their outermost shells. These elements are non-metals. Properties : 1)The elements do not conduct electricity. 2)They also have low melting points and boiling points. NOTE:As we move down the group vii , we note an increase in melting point as well as boiling point. 3)They form acidic oxides. 4)The halogens which are higher up in the group can displace one which is lower down in the group from its salt. Example: Cl + 2NaBr 2NaCl + Br NOTE: The group vii elements can form both ionic and covalent compounds.

7. The Transition Metals:
The transition metals is a series of metals which is found in between Group ii and Group iii of the periodic table. The 1st row of transition metals is found in period 4,between Calcium and Gallium. Properties: 1)The transition metals are good conductors of electricity. 2) They have high densities and hence, they have high melting points and boiling points. 3) They formed coloured compounds. Example: FeCl : Green FeCl : Yellow CuSO : Blue 4)They have different oxidation number(variable valency). Example:Fe / Fe 5)They can act as catalyst.( Fe is used as catalyst in the manufacture of ammonia gas in the Haber Process).

8. Group viii elements and its properties:
This group of elements consists of noble gases(inert gases as they are unreactive).It is also known as Group Zero elements.
Properties:
1)They have a stable electronic configuration as they all have 8 electrons in their outermost shells(except helium which has 2 electrons in its outermost shells).
2)These gases are unreactive and they exist in the monatomic form(they are different from the other gases as the other gases exist in the diatomic form).
Example: N , O ,Cl etc…
Uses Of The Noble Gases:
1)Neon and argon are used in electric light bulbs.
2)Helium is used in weather balloons(helium is the 2nd lightest element ;Hydrogen is the lightest element that exists).