Bakut has a poultry farm. He feeds his birds with a protein and fat-rich diet in large amounts. The birds are in good health,but their egg quality is not good.
$(a)$ What should he do to get good production of eggs?
$(b)$ What should he add in the feed to make the shells of the eggs strong?

Name any one method of incorporating desirable characters into a crop variety.

If there is low rainfall in a village throughout the year,what measures will you suggest to the farmers for better cropping?

Discuss various methods for weed control.

Write the modes by which insects affect the crop yield.

Chemical formula of a compound is a symbolic representation of its composition. We should know the following points to write the chemical formulae of chemical compounds:
$(i)$ Symbols of the combining elements.
$(ii)$ Valency of the combining elements.
In order to know the valency,we must calculate the valence electrons present in the atoms.
The electrons present in the outermost shell or valence shell are called valence electrons. The number of electrons in the atoms of some elements are given below. The elements which have one valency are called monovalent.
$(a)$ What is a chemical formula?
$(b)$ Which main points we must know to write the chemical formula of compounds?
$(c)$ Which values do we find associated with the use of formula for various things in daily life?