Q35 of 52 Page 43

Compare the radii of two species X and Y. Give reasons for your answer.

(a) X has 12 protons and 12 electrons


(b) Y has 12 protons and 10 electrons

Radii of Y is less than X.


Here, X has 12 electrons and 12 protons, therefore it is a neutral atom. Y contains 12 protons and 10 electrons so there are 2 more protons that gives Y a charge of +2. The electronic configurations of the two species is as follows:
















X



Y



K L M



K L



2 8 2



2 8



The atomic size of a positive ion (cation) is always smaller than a neutral atom. This is because cation has less number of electrons and hence more nuclear attractions on electrons in cation. Thus the size of a cation is smaller than that of the neutral atom. Hence, atomic radius of Y is smaller than that of X.


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Three elements A, B and C have 3, 4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, give their valencies.

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If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?

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Arrange the following elements in increasing order of their atomic radii.

(a) Li, Be, F, N


(b) Cl, At, Br, I

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Identify and name the metals out of the following elements whose electronic configurations are given below.

(a) 2, 8, 2


(b) 2, 8, 1


(c) 2, 8, 7


(d) 2, 1