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Komal Ojha posted an Question

August 04, 2020 • 21:05 pm

30 points

IIT JAM
Chemistry (CY)

In lattice energy m is used why it is used and i have some more query in the photo also plz solve them

in lattice energy M is used why it is used and i have some more query in the photo also plz solve them

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Suman Kumar

e is charge of eletron
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sir i know e means charge on electron i.e when z1 and z2 both are e then e^2 is there
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but why z1 and z2 and e^2 both are used
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Suppose you have Al ³+. what is the charge then?
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3*e right
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Here z value is 3. But charge is 3e
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Got it Komal
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Priyanshu kumar Best Answer

Madelung constant is pure number and depends upon crystal structure.. It is basically used in determining the electrostatic potential of a single ion in a crystal by approximating the ions by point charges. Derivation requires mathematical concept ..but know this much it differ from crystal structure to structure. Suppose in 3d crystal lattice ions are there positive and negative alternatively...attraction between opposite charges and repulsion between same charges...So to derive the electrosatic potential of whole crystal lattice we take any ions as reference ion and calculate the electrostatic potential of whole crystal lattice accordingly..Thus madelung constant is helpful
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your 2nd doubt as Electrostatic potential energy formula is this much only P.E =K q1q2/r...when both the charges are electronic charges then we use PE=Ke^2/r
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but in this formula z1 z2 e^2both are used
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komal e is here for elementary charge and Z+ for cation charge number and z- anion charge number..For total cations and anions in crystal lattice we are considering this
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