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 Multiple Choice QuestionsShort Answer Type

101. Define atomic size or atomic radius of an element. Why is it not possible to determine its absolute value?
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 Multiple Choice QuestionsLong Answer Type

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102.

What do you mean by covalent radius?


The covalent radius (or covalent atomic radius) is defined as half of the distance between the nuclei of two like atoms forming a single covalent bond.
rcov = 1/2 [Internuclear distance between two bonded atoms]
For example, for hydrogen molecule, the internuclear distance between two hydrogen atoms is 74 pm.

where 198 pm = Internuclear distance between two chlorine atoms (Cl—Cl) in a molecule of Cl2.
In case of heteronuclear molecules (containing different atoms) such as HCl, the covalent radius may be defined as: “The difference of the distance between the nuclei of two bonded atoms and covalent radius of one of the atoms in a heteronuclear molecule.”
Covalent radius = [Internuclear distance of two bonded atoms] -[Covalent radius of one of the two atoms in heteronuclear molecules]
For example,
Covalent radius of H-atom (in HCl)
= Internuclear distance of HCl - covalent radius of Cl atom
= 136 pm - 99 pm = 37 pm.


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103.

How do atomic radius vary in a period and in a group? How do you explain the variation?

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 Multiple Choice QuestionsShort Answer Type

104.

Why do the noble gas elements have exceptionally high atomic radii?
Or
In a period, generally the size of the atom decreases with rise in atomic number, but at the end of each period, atomic size of the noble gas increases abruptly. Why is it so?

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 Multiple Choice QuestionsLong Answer Type

105. Define vander Waal’s radius and compare it with covalent radius.
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 Multiple Choice QuestionsShort Answer Type

106.

Atomic radii of noble gases are essentially the vander Waal's radii. Comment.

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107.

What is ionic radius?

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108.

Why is the radius of cation less than that of parent atom?

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109.

Why is the radius of anion more than that of the parent atom?

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 Multiple Choice QuestionsLong Answer Type

110.

What does atomic radius and ionic radius really mean to you?

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