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Classification of Elements and Periodicity in Properties

Short Answer Type

111. Describe the theory associated with the radius of an atom as it gains on electron.

Gain of the electron: When a neutral atom gains one electron to form an anion, its radius increases. In the anion, the nuclear charge is the same as that of the parent atom but the number of electrons has increased. Since same nuclear charge now attracts the greater number of electrons, therefore, a force of attraction of the nucleus on the electrons of all the shells decreases i.e. effective nuclear charge per electron decreases in the anion and hence electron cloud expands. The relative sizes of the chlorine atom and chloride ion have been shown.

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112. Describe the theory associated with the radius of an atom as it loses on electron.

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Long Answer Type

113. What do you understand by iso-electronic ions? In iso-electronic ions, the value of ionic radius decreases with the increase in atomic number. Explain.

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114.

What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.
(i) F^- (ii) Ar (iii) Mg²⁺ (iv) Rb⁺

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115.

Consider the following species : N^3-, O^2-, F^-, Na⁺, Mg²⁺ and Al³⁺(a) What is common in them?

(b) Arrange them in the order of increasing ionic radii.

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Short Answer Type

116. For each of the following pairs, state which one is larger in size and why?
(i) Na, Na⁺ (ii) Br, Br^- (iii) Br, I

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117.

Give the formula of a species which will be isoelectronic with the following atoms or ions:
(i) Na²⁺
(ii) Cl^-(iii) Ca²⁺
(iv) Rb⁺.

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118.

Which of the following species will have the largest and the smallest size?
Mg, Mg²⁺, Al, Al³⁺.

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119.

Arrange the following ions in order of increasing size:
Be²⁺, Cl^-, S^2-, Na⁺, Mg²⁺, Br^-.

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Long Answer Type

120.

In each of the following pairs, which species has a larger size? Explain.
(i) K or K⁺
(ii) Br or Br^-
(iii) O^2- or F^-(iv) Li⁺ or Na⁺
(v) P or As
(vi) Na⁺ or Mg²⁺

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