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प्रश्न
What does atomic radius and ionic radius really mean to you?
उत्तर १
Atomic radius is the radius of an atom. It measures the size of an atom. If the element is a metal, then the atomic radius refers to the metallic radius, and if the element is a non-metal, then it refers to the covalent radius. Metallic radius is calculated as half the internuclear distance separating the metal cores in the metallic crystal. For example, the internuclear distance between two adjacent copper atoms in solid copper is 256 pm. Thus, the metallic radius of copper is taken as `256/2 "pm"=128 "pm"`.
Covalent radius is measured as the distance between two atoms when they are found together by a single bond in a covalent molecule. For example, the distance between two chlorine atoms in chlorine molecule is 198 pm. Thus, the covalent radius of chlorine is taken as `198/2 "pm"=99 "pm"`.
Ionic radius means the radius of an ion (cation or anion). The ionic radii can be calculated by measuring the distances between the cations and anions in ionic crystals.
Since a cation is formed by removing an electron from an atom, the cation has fewer electrons than the parent atom resulting in an increase in the effective nuclear charge. Thus, a cation is smaller than the parent atom. For example, the ionic radius of Na+ ion is 95 pm, whereas the atomic radius of Na atom is 186 pm. On the other hand, an anion is larger in size than its parent atom. This is because an anion has the same nuclear charge, but more electrons than the parent atom resulting in an increased repulsion among the electrons and a decrease in the effective nuclear charge. For example, the ionic radius of F– ion is 136 pm, whereas the atomic radius of F atom is 64 pm.
उत्तर २
- Atomic radius:- The distance from the center of nucleus to the outermost shell o electrons in the atom of any element is called its atomic radius. It refers to both covalent or metallic radius depending on whether the element is a non-metal or a metal.
- Ionic radius:- The Ionic radii can be estimated by measuring the distances between cations and anions in ionic crystals.
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संबंधित प्रश्न
What do you understand by isoelectronic species? Name a species that will be isoelectronic with the following atom or ion:-
F-
What do you understand by isoelectronic species? Name a species that will be isoelectronic with the following atom or ion:-
Ar
What do you understand by isoelectronic species? Name a species that will be isoelectronic with the following atom or ion:-
Mg2+
What do you understand by isoelectronic species? Name a species that will be isoelectronic with the following atom or ion:-
Rb+
Consider the following species:-
N3–, O2–, F–, Na+, Mg2+ and Al3+
Arrange them in the order of increasing ionic radii.
Consider the following species:-
N3–, O2–, F–, Na+, Mg2+ and Al3+
What is common in them?
Explain why cations are smaller and anions larger in radii than their parent atoms?
The size of isoelectronic species — F-, Ne and Na+ is affected by ______.
Ionic radii vary in
(i) inverse proportion to the effective nuclear charge.
(ii) inverse proportion to the square of effective nuclear charge.
(iii) direct proportion to the screening effect.
(iv) direct proportion to the square of screening effect.
The correct order of ionic radii for the ions s2−, Cl−, p3−, Ca2+ is ______.
The size of iso-electronic species Cl-, Ar and Ca2+ is affected by ______.
Which one of the following has the largest ionic radius?
