Q49 of 52 Page 45

An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants.

(a) Identify the element X.


(b) Write the electronic configuration of X.


(c) Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals?


(d) What would be the nature (acidic/ basic) of oxides formed?


(e) Locate the position of the element in the Modern Periodic Table.

(a) Element X is sulphur (atomic no. 16).


(b) Electronic configuration of ‘X’ is


K, L, M


2, 8, 6


(c) 2FeSO4 (s) Heat → Fe2O3(s) + SO2 (g) + SO3(g)


(d) SO2 and SO3 are acidic oxides.


(e) It belongs to group 16 and 3rd period.


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47

Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.

(a) Name the elements which have taken the place of these elements.


(b) Mention the group and the period of these elements in the Modern Periodic Table.


(c) Classify these elements as metals, non-metals or metalloids


(d) How many valence electrons are present in each one of them?

 48

(a) Electropositive nature of the element(s) increases down the group and decreases across the period.

(b) Electronegativity of the element decreases down the group and increases across the period.


(c) Atomic size increases down the group and decreases across a period (left to right)


(d) Metallic character increases down the group and decreases across a period.


On the basis of the above trends of the Periodic Table, answer the following about the elements with atomic numbers 3 to 9.


(a) Name the most electropositive element among them.


(b) Name the most electronegative element.


(c) Name the element with smallest atomic size.


(d) Name the element which is a metalloid.


(e) Name the element which shows maximum valency.

 50

An element X of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in presence of the catalyst to form a compound, ammonia which has a characteristic pungent smell.

(a) Identify the element X. How many valence electrons does it have?


(b) Draw the electron dot structure of the diatomic molecule of X. What type of bond is formed in it?


(c) Draw the electron dot structure for ammonia and what type of bond is formed in it?

 51

Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order? Give reason.