Q42 of 52 Page 45

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.

(a) The element placed in 2nd Group and 3rd Period of the Periodic Table is Magnesium (Mg).


(b) Electronic configuration: 1s2, 2s2 2p6 3s2


K, L, M


2, 8, 2


(c) When the magnesium metal burns in oxygen, it produces magnesium oxide.


2Mg(s) + O2(g) → 2MgO(s)


When magnesium oxide is heated with water, magnesium hydroxide is formed.


(d) MgO(s) + H2O(l) → Mg(OH)2(aq)


Electron dot structure:



Magnesium loses two electrons and oxygen gains two electrons to complete the octet structure.


More from this chapter

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40

Identify the elements with the following property and arrange them in increasing order of their reactivity.

(a) An element which is a soft and reactive metal.


(b) The metal which is an important constituent of limestone.


(c) The metal which exists in liquid state at room temperature.

 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”.

 43

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.

 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.