Periodic Cassification of Elements

Part-3

Elements  

are  

classified  

on  

the  

basis  

of  

similarities  

in  

their  

properties.

Dobereiner  

grouped  

the  

elements  

into  

triads  

and  

Newlands  

gave  

the

Law  

of  

Octaves.  

Mendeléev  

arranged  

the  

elements  

in  

increasing  

order

of  

their  

atomic  

masses  

and  

according  

to  

their  

chemical  

properties.

Mendeléev  

even  

predicted  

the  

existence  

of  

some  

yet  

to  

be  

discovered

elements  

on  

the  

basis  

of  

gaps  

in  

his  

Periodic  

Table.  

Anomalies  

in

arrangement  

of  

elements  

based  

on  

increasing  

atomic  

mass  

could  

be

removed   

when   

the   

elements   

were   

arranged   

in   

order   

of   

increasing

atomic  

number,  

a  

fundamental  

property  

of  

the  

element  

discovered  

by

Moseley.  

Elements  

in  

the  

Modern  

Periodic  

Table  

are  

arranged  

in  

18

vertical  

columns  

called  

groups  

and  

7  

horizontal  

rows  

called  

periods.

Elements  

thus  

arranged  

show  

periodicity  

of  

properties  

including  

atomic

size,   

valency   

or   

combining   

capacity   

and   

metallic   

and   

non-metallic

character.