Write the name of a bio-fertilizer.

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?

Once Ravi and Aman were cooking rice in the kitchen and accidentally Aman's hand got a severe burn while opening the lid of the cooking vessel. Immediately,Ravi applied ice on his hand,then applied an ointment,and told him to cook carefully as he had been hurt by steam,and steam causes more severe burns. Aman thanked Ravi and smiled.
$(a)$ According to you,what kind of qualities are shown by Ravi?
$(b)$ How does steam produce more severe burns than boiling water?

$(i)$ Mr. Ramdin,an educated farmer,convinces his friends to use fertilizers judiciously. Why?
$(ii)$ Which two values of Ramdin impress you?

The housing, nutritional and environmental requirements of broilers are somewhat different from those of egg layers.

Name two protein-containing rabi crops.