Q9 of 61 Page 1

Based on the group valency of elements state the formula for the following giving justification for each:

(i) Oxides of 1st group elements,


(ii) Halides of the elements of group 13, and


(iii) Compounds formed when an element of group 2 combines with an element of group 16.

Based on the- group valency of elements state the formula are:


(i) Let the elements of first group is A and let its oxide by denoted by ‘O’.


Since the element is first group, so its valency will be 1 and that of O is 2.


So, the chemical formula can be written as:



So, the formula is: A2O


(ii) Let the elements of group 13 be denoted by ‘M’


Let the halide be denoted by ‘X’


The valency of group M will be +3 and that of halide is -1


So, on cross multiplication of the valency, we get



So, the chemical formula is: MX3


(iii) Let element of group 2 be denoted by X and that of element of group 16 be denoted by ‘Y’


Valency of ‘X’ will be: +2


Valency of ‘Y’ will be -2


On cross multiplication of the valency of X and Y, we get



Therefore, the formula will be: XY


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7

State the meaning of functional group in a carbon compound. Write the functional group present in

(i) ethanol and


(ii) ethanoic acid arid also draw their structures.

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Write the names and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. State the essential conditions required for an addition reaction to occur write the chemical equation giving the name of the reactant and the product of such a reaction.

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(a) Define the following terms:

(i) Valency; (ii) Atomic size


(b) How do the valency and' the atomic size of the elements vary while going from left to right along a period in the modern periodic table?

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