Question

discuss the construction of long form the periodic table

Answer 1

LONG FORM OF PERIODIC TABLE

  Periods

  Periodic table is divided into seven horizontal rows of elements. Each row of elements is called aperiod

ELEMENTS

PERIOD

...  1. Atomic size decreases in a period. 
  2-Nuclear charge increases in a period.
  3-Ionization potential increases in a period.
  4-Electronegativity increases in a period.
  5-Electropositivity and metallic character decreases in period.
  6-Each period starts with Alkali metal and ends on a Noble gas.
  For example:
  2nd period : Li .................................. Ne
  3rd period : Na ..................................Ar
  7-First element of each period is most reactive (electropositive), and last element is chemically inert.

DESCRIPTION OF PERIODS

First period

  It is the shortest period and it contains only two elements (H and He). This period corresponds to filling   up of K-shell. Electronic configuration of the elements of this period is 1s1 and 1s2

Second period

  It is called first short period and it contains eight elements. This period corresponds to filling up of L-shell.   In this period electrons occupy 2s and 2p orbital. This period contain 2 element of s-block and six from 
  p-block

Third period

  It also contains eight elements and is known as second short period. It corresponds to filling up of 
  M-shell. It contains 2 s-block and 6 P-block elements. In this period 3s and 3P orbital are being filled.

Fourth period

  It contains 18 elements and is known as first long period. This period corresponds to the filling up of 
  N-shell. It contains 2 s-block, 6 P-block and 10 d-block (transition) elements. It start with filling of 4s-   orbital followed by 3d and 4p orbital.

Fifth period

  Fifth period contain 18 elements and is known as 2nd long period. It corresponds to filling up of O-shell. It   starts with the filling of 5S-orbital followed by 4d and 5p orbital.

Sixth period

  Sixth period contains 32 elements and it is the longest period. 
  Among 32 elements:
  2 elements of s-block with electronic configuration 6s1 and 6s2.
  6 elements of p-block with electronic configuration 6s2, 6p1 to 6s2, 6p6.
  10 elements of d-block with electronic configuration 6s2, 5d1 to 6s2, 5d10
  14 elements of f-block with electronic configuration 6s2, 5d1, 4f1 to 6s2, 5d1, 4f14.
  In sixth period electrons starts filling 4f-orbital after 5d-orbital accommodate one electron.

Seventh period

  7th period is incomplete period.
  It includes:  2 elements of s-block with electronic configuration 7s1, 7s2  10 elements of d-block with electronic configuration 7s2, 6d1 to 7s2, 6d10  14 elements of f-block with electronic configuration 7s2, 6d1, 5f1 to 7s2, 6d1, 5f14

Groups

  Modern periodic table is divided into eight vertical columns of elements. Each vertical column of elements   is called a "GROUP". The groups of the periodic table are further divided into two sub-groups or families "A   and B". Elements of sub-group "A" are known as Normal elements or Representative elements. While the   elements of sub-group "B" are known as Transition elements. Group numbers is designated by Roman   numbers.

General features of a group are as under

  1-Group number of an element shows the number of electrons in the outermost shell of that element

ELEMENT

NUMBER OF VALENCE ELECTRONS

GROUP

Na 
Cl
C

1
7 
4

I-A
VII-A 
Iv-A

  2-Atomic size increases in group.
  3-Ionization potential of elements decreases down the group.
  4-Electronegativity decreases down the group.
  5-Metallic character increases down the groups.

BLOCKS

  On the basis of valence shell electronic configuration, periodic table is divided into four distinct blocks of   elements.

  1. s-block

  2. p-block

  3. d-block

  4. f-block

S-block elements

  All the elements in which last electron enters "ns" orbital are known as s-block elements. 
  Elements of group I-A and II-A belong to s-block. 
  Their valence shell electronic is ns1 to ns2.
  All the elements of s-block are very reactive and electropositive in nature. 
  S-block elements are good reducing agents.
  They form ionic compounds. 
  They are all metals and solid. They are low density metals.
  For example :
  Li (z=3) 1s2, 2s1
  Na (z=11) 1s2, 2s2, 2p6, 3s1
  Be (z=4) 1s2, 2s2

p-block elements

  The elements in which valence electrons enter p-orbital and this orbital is progressively filled are 
    called p-block elements. 
  Their valence shell electronic configuration is from ns2, np1 to ns2, np6. 
  P-block consists of the elements of group III-A to VIII-A (zero-group). 
  They include metals, nonmetals and metalloids. 
  There are 30 elements in six sub-groups of p-block.

d-block elements

  The elements in which last electron enters (n-1) d-orbital are called d-block elements or outer transition   elements. 
  Valence shell electronic configuration of these elements is ns2, (n-1) d1-10. 
  All these elements are metals.There are four series of outer transition elements.
  Fourth series is incomplete.

Answer 2

modern periodic table's main credit goes to mendleev .
but the limitations of our Mendeleev's table are competed by modern periodic table made by Henry mooselay