Q43 of 52 Page 45

An element X (atomic number 17) reacts with an element Y (atomic number 20) to form a divalent halide.

(a) Where in the periodic table are elements X and Y placed?


(b) Classify X and Y as metal (s), non-metal (s) or metalloid (s).


(c) What will be the nature of oxide of element Y? Identify the nature of bonding in the compound formed.


(d) Draw the electron dot structure of the divalent halide.

(a) Element X belongs to Group 17 and 3rd period. X is Cl (chloride).


Element Y belongs to Group 2 and 4th period. Y is Ca (calcium).


(b) X is a non-metal and Y is a metal.


(c) Metals always combine with oxygen to form basic oxides. Basic oxides react with acids to form salt and water.


In a reaction, meals lose electrons and non-metals gain electrons. Thus positive and negative ions are formed. This creates a strong electrostatic force between these ions. These strong electrostatic forces form the ionic bonds.


(d) Electron dot structure



Electron dot structure for calcium chloride



More from this chapter

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41

Properties of the elements are given below. Where would you locate the following elements in the periodic table?

(a) A soft metal stored under kerosene.


(b) An element with variable (more than one) valency stored under water.


(c) An element which is tetravalent and forms the basis of organic chemistry.


(d) An element which is an inert gas with atomic number 2.


(e) An element whose thin oxide layer is used to make other elements corrosion resistant by the process of “anodising”.

 42

An element is placed in 2nd Group and 3rd Period of the Periodic Table, burns in presence of oxygen to form a basic oxide.

(a) Identify the element.


(b) Write the electronic configuration.


(c) Write the balanced equation when it burns in the presence of air.


(d) Write a balanced equation when this oxide is dissolved in water.


(e) Draw the electron dot structure for the formation of this oxide.

 44

Atomic numbers of a few elements are given below 10, 20, 7, 14.

(a) Identify the elements.


(b) Identify the Group number of these elements in the Periodic Table.


(c) Identify the Periods of these elements in the Periodic Table.


(d) What would be the electronic configuration for each of these elements?


(e) Determine the valency of these elements.

 45

Complete the following cross word puzzle (Figure 5.1)


Across:


(1) An element with atomic number 12.


(3) Metal used in making cans and member of Group 14.


(4) A lustrous non-metal which has 7 electrons in its outermost shell.


Down:


(2) Highly reactive and soft metal which imparts yellow colour when subjected to flame and is kept in kerosene


(5) The first element of second Period


(6) An element which is used in making fluorescent bulbs and is second member of Group 18 in the Modern Periodic Table


(7) A radioactive element which is the last member of halogen family.


(8) Metal which is an important constituent of steel and forms rust when exposed to moist air.


(9) The first metalloid in Modern Periodic Table whose fibres are used in making bullet-proof vests