Q20 of 31 Page 198

On the basis of atomic number predict to which block the elements with atomic number 9, 37, 46 and 64 belongs to?

Atomic number 9:


The electronic configuration = 1s2 2s2 2p5


The number of valence electrons = 7


Period number = 7


This means the element having atomic number 9 belongs to p-block.


Atomic number 37:


The electronic configuration = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s1


The number of valence electrons = 1


Period number = 1


This means the element having atomic number 37 belongs to s-block.


Atomic number 46:


The electronic configuration = [Kr]4d10


The number of valence electrons = 10


Period number = 10


This means the element having atomic number 46 belongs to d-block.


Atomic number 64:


The electronic configuration = [Xe] 4f7 5d1 6s2


The new electron enters into the f-orbital.


This means the element having atomic number 64 belongs to f-block.


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18

What is a periodic property? How do the following properties change in a group and period? Explain.

(a) Atomic radius


(b) Ionization energy


(c) Electron affinity


(d) Electro negativity.


(b) Explain the ionization energy order in the following sets of elements:


a) Na, Al, Cl b) Li, Be, B


c) C N, O d) F, Ne, Na c) Be, Mg, Ca

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Name two elements that you would expect to have chemical properties similar to Mg. What is the basis for your choice?

 21

Using the periodic table, predict the formula of compound formed between and element X of group 13 and another element Y of group 16.

 22

An element X belongs to 3rd period and group 2 of the periodic table. State

(a) The no. of valence electrons


(b) The valency


(c) Whether it is metal or a nonmetal.