Elements of Group 1 & 2

Introduction : 

group 1st  and group 2nd are also known as S block elements

Group first contain:  hydrogen, lithium, sodium, potassium, rubidium, cesium, francium 

Group second contain  : Beryllium, magnesium, calcium, strontium, barium, radium

in this chapter we are going to see the physical and chemical properties of group first and 

second elements step by step first of all we start from hydrogen.

Hydrogen : 

Hydrogen is the first element in the periodic table. It placed at the top of the group first of 

the alkali metal , but it differs from alkali metal in number of respects and hence it  studied 

separately 

hydrogen atom consist of nucleus of  +1  charge And one extra nuclear electron,

 hydrogen has less  tendency to lose this electron however it bears this one with other electron

 to form covalent bond it exists in diatomic form as a H molecule therefore it is called as

 dihydrogen 

Occurrence :

In the free state hydrogen exist as dihydrogen gas. It is most abundant elements in universe

It is also the main element in solar system. It is the 10th most abundant element on the 

basis of mass 

Position of hydrogen in periodic table : 

electronic configuration of Hydrogen in periodic table 

the outer electronic configuration is similarly to those of alkali metals, belonging to group first. 

but it also resemble as electronic configuration of group 17 elements by adding one 

electron to hydrogen we get noble  gas 

Isotopes of Hydrogen : 

Different atom of same element having same atomic number but different atomic mass 

number is called as Isotopes Hydrogen has three isotopes 

They  contain one proton and one electron but different number of neutrons in nucleus