LONG FORM OF PERIODIC TABLE

-

In Long form periodic table elements have been arranged in the increasing order of their atomic mass and also based on electronic configuration. 

This periodic table consists of

(i) 7 horizontal rows known as periods. 

(ii) 18 vertical columns known as groups. 

(iii) 4 blocks

Periods

There are seven periods in the periodic table. The number of elements in each period corresponds to number of electrons in different major energy levels. Each period starts with a new principle quantum number. 

  • The horizontal rows from left to right in the periodic table are called periods. 
  • There are 7 horizontal rows. So there are 7 periods. 
  • The number of elements in each period corresponds to number of electron in different energy levels. 
1st PERIOD

This period corresponds to first energy level, whose capacity is two electrons. So there are two elements present in the 1st period. They are H(1s1) , He (1s2) . It is the shortest period. 

2nd  PERIOD

It corresponds to second energy level, whose capacity is 8 electrons. So there are 8 elements present in 2nd period, It starts with element Li (1s2, 2s1)  and ends with element Ne (1s2, 2s2 2p6) . 

3rd PERIOD

It corresponds to third energy level. 3d orbital has higher energy than 4s orbital, 3d orbital is filled after filling 4s orbital. So third period involves the filling of only 3s and 3p orbitals. Therefore, it contains 8 elements. This period starts with Na (1s2, 2s2 , 2p6 , 3s1 ) and ends with Ar (1s2 , 2s2 , 2p6, 3s2 , 3p6 ) . 

4th PERIOD

This period corresponds to filling of electrons in 4th energy level. As 3d orbital is present in between 4s and 4p . So 3d orbital is filled in between 4s and 4p orbitals. The number of elements present in 4th period corresponds to filling of electrons in 4s, 3d and 4p . So there are 18 elements present in the 4th period. This period starts with the element K ([Ar] 4s1 ) and ends with Kr ([Ar] 3d10 , 4s2 , 4p6 ) . 

5th PERIOD

It corresponds to filling of electrons in 5th energy level as 4th energy level. As 4d orbital is present in between 5s and 5p , 4d orbital is also filled. So the number of elements present in 5th period corresponds to filling of electrons in 5s, 4d and 5p . It starts with element (Rubidium) Rb ([Kr] 5s1 ) and ends with element Xenon. 

6th Period

It starts with the element Cs (Cesium) and ends with the element Rn (Radon). This period corresponds to filling of electrons in 6s, 4f, 5d, 6p . In Cs the last electron enters into 6s orbital in Radon the last electron enters into 6p orbital, The elements from 57 (Lanthanum) to 71 (Lutetium)  are placed separately below the periodic table as these are f- block elements. It contains 32 elements which is the period in the periodic table. 

7th PERIOD

7th period is incomplete period. It starts from the elements 87 Fr (Francium). The 7th period elements are mainly radioactive  . The elements upto Uranium are naturally occurring and remaining elements are artificially prepared, So the elements having atomic number greater than 92 are synthetic elements. This period corresponds to filling of electron in 7s, 5f, 6d, 7p . In this period the elements from the atomic number 89 (Actinium) to atomic number 103 (Lawrencium) are placed separately below the periodic table as they are f- block elements. 





Description of periods

Period        Subshells          Total no.of elements 

1st                     1s                                           2

2nd                  2s 2p                                        8

3rd                   3s  3p                                       8

4th                   4s  3d  4p                                 18

5th                   5s  4d  5p                                  18

6th                   6s  4f  5d  6p                             32

7th                   7s  5f  6d  7p                             32




Comments

Post a Comment

Popular posts from this blog

PERIODIC PROPERTIES

-
Image
  ATOMIC RADIUS Atomic radius is defined as the distance from the center of the nucleus to the outer most shell of electrons.  Probability of finding the electron is never zero even at large distance from the nucleus. Based on probability concept, an atom doesn't have well defined boundary. Hence it is very difficult to determine the atomic radius.  Atomic radius is taken as the effective size which is the distance of the closest approach of one atom to another atom in a bonding state.  The atomic radius can be determined as (a) Covalent radius (b) Vander waal's radius (c) Metallic radius (d) Ionic radius Covalent radius One half of the inter-nuclear distance between the two covalently bonded atom is called covalent radius.  Covalent radius can be determined in case of the atoms which are attached to each other by covalent bond.  r covalent = Inter-nuclear distance between two covalently bonded atoms / 2 (i) For homoatomic molecules d A-A = r A + r A Or,...
Read more

BLOCKS OF ELEMENTS

-
Image
  Periodic table is divide into 4  blocks known as S, p, d, f  blocks. The classification of the elements depends upon the type of sub-shell in which last electron of the element enters.  S - Block elements   The element in which last electron enters into s - subshell  are called s - block element.  The general electronic configuration of s - block elements are  ns 1-2   .  The s - block elements are present in the left side of the periodic table.  Group 1 and Group 2 elements as well as Helium of zero group are known as the s - block elements. All s - block elements are normal elements. Characteristics of s - block elements (i) The elements have low ionization energy.  (ii) They are soft metal having low melting and boiling point.  (iii) They are highly reactive.  (iv) They are good reducing agents.  (v) They give to the flame.  p - block elements The elements in which last electrons enters into p - subshel...
Read more