PERIODIC TABLE

 Modern Periodic table

Modern Periodic Law : 

The recent work has established that the fundamental property of an atom is atomic number and not atomic weight. Therefore, atomic number is taken as the basis of the classification of the elements. The modern periodic law was given by Moseley, it may be stated as : ''The properties of elements are periodic functions of their atomic number".

Modern periodic table is also called long form of the periodic table or Bohr’s table. In this table, the elements are arranged in order of their increasing atomic number. It consists of 4 blocks (s, p, d and f), 18 groups numbered from 1 to 18 and 7 periods numbered from 1 to 7.

Short tricks to learn periodic table 

Blocks :

The periodic table is divided into four main blocks (s, p, d and f) depending upon the subshell to which the valence electron enters into. 

(1) Elements of group 1 and 2 constitute s-Block. 

 (2) Elements of group 13, 14, 15, 16, 17, 18 constitute p-Block. 

 (3) Elements of group 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 constitute d-Block. 

(4) The f-Block elements comprise two horizontal rows placed at the bottom of the periodic table to avoid its unnecessary expansion. 

Elements of s- and p-blocks are called normal or representative elements, those of d-block are called transition elements while the f-block elements are called inner transition elements.

Periods :

The horizontal rows are called periods. There are seven periods in the long form of the periodic table,

(1) Ist period ( H ⟶ He) contains 2 elements. It is the shortest period. 

(2) 2nd period (  Li ⟶ Ne) and 3rd period (  Na ⟶ Ar) contains 8 elements each. These are short periods.

 (3) 4th period ( K⟶ Kr) and 5th period (  Rb ⟶ Xe) contains 18 elements each. These are long periods.

 (4) 6th period (  Cs ⟶ Ra )consists of 32 elements and is the longest period.

 (5) 7th period starting with Fr  is incomplete and consists of 19 elements.

 

Groups: 

The 18 vertical columns are called groups. The elements belonging to a particular group is known as a family and is usually named after the first number. Apart from this some of the groups are given typical names as examplified beneath,

(1) Elements of group 1 are called Alkali-Metals.

(2) Elements of group 2 are called Alkaline Earths. 

(3) Elements of group 3 are called Pnicogens.

(4) Elements of group 16 are called Chalcogens.

(5) Elements of group 17 are called Halogens.

(6) Elements of group 18 are called Noble Gases or Aerogens.

All the other groups are named after the first member of each group.

NOMENCLATURE OF ELEMENTS WITH ATOMIC NUMBERS > 100

The naming of the new elements had been traditionally the privilege of the discoverer (or discoverers) and the suggested name was ratified by the IUPAC. In recent years this has led to some controversy. The new elements with very high atomic numbers are so unstable that only minute quantities, sometimes only a few atoms of them are obtained. Their synthesis and characterisation, therefore, require highly sophisticated costly equipment and laboratory. Such work is carried out with competitive spirit only in some laboratories in the world. Scientists, before collecting the reliable data on the new element, at times get tempted to claim for its discovery. For example, both American and Soviet scientists claimed credit for discovering element 104. The Americans named it Rutherfordium whereas Soviets named it Kurchatovium. To avoid such problems, the IUPAC has made recommendation that until a new element’s discovery is proved, and its name is officially recognised, a systematic nomenclature be derived directly from the atomic number of the element using the numerical roots for 0 and numbers 1-9.These are shown in Table

 The roots are put together in order of digitswhich make up the atomic number and “ium” is added at the end. The IUPAC names for elements with Z above 100 are shown in Table