PERIODIC TABLE

WEEK: 1

The arrangement of elements in the Periodic table is very important in chemistry. Dmitri Mendeleev, a Russian scientist was the first to develop Periodic Table in 1869. He arranged the elements in order of increasing relative atomic mass.

He observed that elements with similar properties kept recurring at regular intervals or periods.
His Periodic Table had many gaps.
He predicted that there were undiscovered elements which could fill the gaps.
He also predicted the properties of the elements.

 

The discovery of the electronic structure of atoms however later revealed that elements vary in their properties according to their atomic number and not their relative atomic mass. This is the basis of the modern periodic law.

 

The modern Periodic Law states that the properties of the elements are a periodic function of their atomic numbers.

 

 

Features of the modern Periodic Table

 

It is divided into 8 vertical columns called Groups and 7 horizontal rows called periods.

 

GROUPS:

1. They are numbered from 0 to 7.
2. They constitute of elements of similar chemical properties.
3. Elements in the same group have the same number of electron in the outermost shell of their atoms.
4. The transition elements occupy the gap between Group 2 and 3.
5. For Groups I,II,III,IV and 0, the oxidation state of the elements is the same as the Group number.
6. Groups V, VI and VII, main oxidation state is eight minus the group number. 
7. The transition elements show variable oxidation states.CLICK HERE TO CONTINUE

PERIODS:

1. They are numbered from 1 to 7.
2. Elements in the same period have the same number of electron shells which correspond to the Period.
3. The number of valence electrons of the elements in the same Period increases progressively by one across the Period from left to right.
4. The elements of the lanthanide and actinide series are among the Periods 6 and 7 respectively.
5. These elements are known as the inner transition elements CLICK HERE TO CONTINUE