Chemical Formula

The combining capacity of elements or atom is known as valency, and valency can be used to find out how the atom of elements Will combine with atom of another elements to form a chemical compounds.

Chemical formula is showing all constituents of chemical compounds by chemical symbol in a fixed proportion or according to the valency of elements or atom.

Example: NaCl, HCl, NaF, NaBr, ZnO etc

Rule for writing the chemical Formulae

  • In case simple molecular compounds  that is  those which are made up of  only two elements and hence also called binary compounds  the symbol of two elements written side by side and their respective valency are  written  below their symbol.
  • In case of simple ionic compound that is compound made up of mono atomic ion the symbol of metal atom (forming the anion)  written first and their followed by the Symbol of non metal and their  respective valencies are written below of the symbol.
  • In case of ionic compound containing polyatomic ion the formula of polyatomic ion written in bracket and valencies are written below as in the above cases.
  • In any of the above case if there is common factor between the cation and anion the valencies are divided by common factor.
  • Finally we apply criss-cross that is cross over the valencyor the charges that they appear to lower right hand  side of the symbol is omitted Similarly sign of the charges of the ion are omitted.
  • For 1 appear  on the lower right hand side of a polyatomic ion ,  the bracket of polyatomic ion  are also omitted.

Example:

1) Chemical formula of simple molecular compounds:

• Formula of hydrogen chloride: the elements present in hydrogen and chlorine.

• The electronic configuration of hydrogen is 1 , and chlorine is 2,8,7, so both the elements are unstable and become stable both needed one electrons so the share their electrons each other and become stable and make compounds HCl.

2) Formula of water: the elements present in hydrogen and oxygen.

• The electronic configuration of hydrogen is 1 , and oxygen is 2,6 , so both the elements are unstable and become stable both needed the share their electrons each other and become stable and make compounds H2O.

3) Formula of hydrogen sulphide: the elements present in hydrogen and sulphur:

Chemical Formula

 

Question answer:

1) What is chemical formula?

Answer: Chemical formula is showing all constituents of chemical compounds by chemical symbol in a fixed proportion or according to the valency of elements or atom.

2) Write the rules of writing chemical formula?

Answer: following are the rules of writing a  chemical formula

  • In case simple molecular compounds  that is  those which are made up of  only two elements and hence also called binary compounds  the symbol of two elements written side by side and their respective valency are  written  below their symbol.
  • In case of simple ionic compound that is compound made up of mono atomic ion the symbol of metal atom (forming the anion)  written first and their followed by the Symbol of non metal and their  respective valencies are written below of the symbol.
  • In case of ionic compound containing polyatomic ion the formula of polyatomic ion written in bracket and valencies are written below as in the above cases.
  • In any of the above case if there is common factor between the cation and anion the valencies are divided by common factor.
  • Finally we apply criss-cross that is cross over the valency  or the charges that they appear to lower right hand  side of the symbol is omitted Similarly sign of the charges of the ion are omitted.
  • For 1 appear on the lower right hand side of a polyatomic ion ,  the bracket of polyatomic ion  are also omitted.

3) Give the example of simple chemical formula?

Answer: •  Formula of hydrogen chloride: the elements present in hydrogen and chlorine.

  • The electronic configuration of hydrogen is 1 , and chlorine is 2,8,7, so both the elements are unstable and become stable both needed one electrons so the share their electrons each other and become stable and make compounds HCl.

                                                                          H1 Cl1    

but one is negligible or omitted by the rule so formula can be written as  = HCl.

4) Write the chemical formula of sodium chloride?

Answer:  Formula of sodium chloride:

Symbol  :                   Na           Cl

Charge :                     1+             1

Valency:                     1             1

So, Na1+ and Cl1- charge  is negligible or omitted. By the rules.

Chemical formula:  NaCl

5) Give the example of polyatomic ions chemical formula?

Answer:   Formula of calcium nitrate :    Ca(NO3)2

Symbol: CaNO3

Charge :   2+             1

Valency:  2          1

Chemical formula: Ca(NO3)2


Leave a Reply

Your email address will not be published. Required fields are marked *

18 + thirteen =