Category Archive : chemistry

Basics of Periodic Table,|Important For CDS|NDA|AFCAT Exams

Most abundant element on earth’s crust – Oxygen
Most abundant metal in earth’s crust – Aluminium
Most abundant metalloid in earth’s crust – Silicon
Most abundant element in atmosphere – Nitrogen
Most abundant element in the universe – Hydrogen
Most abundant element in human body – Oxygen
Most abundant gas in atmosphere – Nitrogen
Most abundant element in sea water – Chlorine
Most abundant element in moon’s surface – Titanium
Most abundant metal present in human body and bones – Calcium
Most abundant metal compound in bones – Calcium phosphate
Most abundant compound on earth’s surface – Water (H2O)
Most abundant compound in sea water – Sodium Chloride
Second most abundant compound in sea water – Magnesium Chloride

Most chemically reactive element – Fluorine
Second most chemically reactive element – Chlorine

The lightest and simplest element – Hydrogen
The lightest metal – Lithium

*The rarest element in the earth – Astatine

The heaviest element – Osmium
The heaviest gaseous element – Radon

First man made element – Technetium
Most stable element – Lead

The periodic table is divided into 4 main blocks

S block – elements of group 1 and 2
*P block – elements of group 13 to 18
*D block – elements of group 3 to 12
*F block – Lanthanides and Actinides 

*The longest period of the periodic table 
Ans : Sixth period

The shortest period of the periodic table
Ans : First period

*Elements with atomic number 57-71 are known as
Ans : Lanthanides (rare earths) 

*Elements with atomic number 89-103 are known as
Ans : Actinides (radio active rare earths) 

*Total number of elements in periodic table 
Ans : 118

*The number of naturally occurring elements
Ans : 92