Please enable JavaScript.

Coggle requires JavaScript to display documents.

Periodic Classification Of Elements [Class 10 Chemistry] - Coggle Diagram

Periodic Classification Of Elements

[Class 10 Chemistry]

Early attempts of Classification

Newlands Law Of Octaves
Every 8th element after the first will have the properties similar to the first one.

--
Drawbacks

➡️ It was applicable only upto Calcium as after that every 8th element did not have similar properties to the first one .

➡️ Newlands considered that there were only 56 Elements in nature and didnt leave any space for elements to be discovered in the future.

➡️ Cobalt & Nickel are in the same slot and are placed with fluroine , chlorine & bromine which have completely different properties & Iron which has similar properties to them is placed far away in the table 😂

1 para ki beizzati for Newlands

Mendeleev's PERIODIC TABLE
According to Mendel , the properties of elements are a periodic function of their atomic masses
Which means that atomic mass influenced elements' properties

ACHIEVEMENTS OF MENDELEEVS PEIODIC TABLE

➡️ He placed some elements before others even if they had higher atomic masses so that elements with similar properties could be grouped together.

➡️ He left some gaps in his table & predicted that some elements which are not discovered yet will be placed here .He named these yet to be discovered elements as :- Eka-Boron = scandium , Eka-Aluminum  = gallium, Eka-Silicon = germanium

➡️ When inert gases were discovered and added in his table , it didn't disturb the position of other elements which was an extraordinary achievement

Drawbacks Of Mendeleev's Table

  ➡️ Hydrogen had similar properties to both alkali metals and Halogens , hence they can't be placed in the column with alkali metals . Clearly no place could be given to hydrogen & hence he could not give a proper position to it in the table.

➡️ Isotopes (same atomic number but different atomic masses) could not be placed in the table as it would completely disturb it . This is the reason modern periodic table uses atomic number as a base for classification.

 ➡️ Atomic Masses do not increase by a fixed number in elements . They increase in an irregular manner.

Koi kitna bhi acha kam karle NCERT wale drawbacks de dete hai . Book ke end me NCERT padne ke drawbacks bhi hone chahiye . Who agrees ? Like thoko aur apni screen tod do

Modern Periodic Table

See on page 86 of NCERT

About the MODERN PERIODIC TABLE

 1) It has 118 elements.


 2) It has 18 vertical columns (groups)& 7 horizontal rows (periods).


 3) Periods have elements with same number of shells .


 4) Groups have elements with same number of valence electrons.

Some Random Things

♦️ Hydrogen has no "appropriate" position in the Periodic Table because it has properties similar to  Alkali metals as well as Halogens

♦️ Number of Electrons which can come in a shell is given by the formula 2n² where n is the shell number . So for example shell 2 i.e. L Shell will have 2(2)² = 8 electrons

Trends in Periodic Table (Most imp topic)

                ♣️ VALENCY

 As we move from left to right in periodic table , the valency increases . This means that across a period (horizontal row) , the valency increases

                ♣️ ATOMIC SIZE 

The atomic radius decreases from left to right across a period . It is because as the number of protons increase , the EFFECTIVE NUCLEAR CHARGE also increases which causes the electrons to come closer to the nucleus and thereby reduce its size .

    ♣️ Metallic & Non Metallic properties 

Metallic charcter is the willingness or rather the ease with which an atom loses an electron & Non Metal is the exact opposite of it . As we move from top to bottom , the metallic character increases & non-metallic charcter decreases . Why ? Because the number of shells in the atom increase as we go towards the bottom and hence , the EFFECTIVE NUCLEAR CHARGE (The attraction between protons and valence electrons) decreases and so the atom loses the electron easily . 

Also , Metallic Character decreases & Non metallic charcter increases from left to right because the number of valence electrons increases and hence , the ABILITY to take electrons also increases.

Note : Non metallic character is same as electronegativity (ability to take electrons) and Metallic character is same as electropositivity (ability to lose/give electrons)