ICSE Class 8 Answered

i. Valency

   Valency is the combining capacity of an element or a radical.  

Example: 

     Valency of carbon is 4 because it combines with four atoms of hydrogen to yield methane (CH₄). 

 ii. Radical

    Radical is an atom or a group of atoms of same or different elements which behaves as a single atom with a  

    positive or a negative charge on it. 

    Radicals have their own combining power based on which they form chemical formulae. 

 Example: 

    NH₄⁺, Na⁺, NO₃^-, SO₄² 

 iii. Molecular formula

     Molecular formula of a compound is the symbolic representation of its molecule. 

     It shows the number of atoms of each element present in it. These atoms combine in whole number to form the

     molecule.  

 Example: 

     Nitric acid HNO₃ 

     Potassium nitrate  KNO₃