How to Find out the Order of the Ionic Radius – Part 1

Ionic radius is the radius of a monatomic ion in an ionic crystal structure.


Although neither atoms nor ions have sharp boundaries, they are treated as if they were hard spheres with radii s.t. the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice.

Factors affecting anionic radius (r─):

  1. # of shells (principal quantum number, n): n ↑ => r─ ↑ (going down the group)
  2. Nuclear charge Z (# of protons): Z ↑ => r─ ↓ (across the period, left to right)
  3. Negative charge (e─): e─ ↑ => r─ ↑ (∵ repulsion => Cloud expansion)

Therefore, the order of the ionic radius is not necessarily that of the atomic radius.

Question:

What is the decreasing order of the ionic radius for the following species?

I─, Se2─, Br─, O2─, F─

Solution:



Click/tap to enlarge the image

The order may depend on specific reported crystal radii data sets.

Irregularity in the ionic radii❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

‌‌(1)    Ncert. Chemistry : Textbook for Class XI - Part.I; National Council Of Educational Research And Training: New Delhi.

(2)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

(3)    Wikipedia Contributors. Ionic Radius; Wikimedia Foundation, 2019. https://en.wikipedia.org/wiki/Ionic_radius.

Comments

Post a Comment

Popular posts from this blog

How to Predict where an Electrophilic Aromatic Substitution May Occur in a Ring – Part 3

Image
An organic reaction in which an atom attached to an aromatic system (usually hydrogen) is substituted by an electrophile is referred to as  electrophilic aromatic substitution  ( S E Ar  or  EAS ). One of the most important  EASs  is halogenation. If Bromine water is added to Aniline, a multi-substituted product ( 2,4,6 -derivative) is obtained as Aniline is a strongly activating group (the same happens to Phenol). To generate the mono-substituted product, a protection, say, an acyl group is required. Question: Predict the major product(s) of the following reaction: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image Motivated by EAS ❓ Let Chemaficionado know  in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Electrophilic aromatic substitution . Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution. (2)    ...
Read more

How to Carry out a Multistep Synthesis – Part 4

Image
Multistep synthesis  is the artificial execution of multiple organic chemical reactions to obtain one or more products by physical and chemical manipulations. Retrosynthetic analysis is a problem-solving approach in the organic syntheses, achieved by transforming a target molecule into simpler precursor structures regardless of any potential reactivity/interaction with reagents, and repeated until a simple or commercially available structure is reached, which can be used as a starting material to synthesize the target molecule. Question: How would you do the following transformation? Click/tap here to enlarge the image Solution infographic: Click/tap here to enlarge the image Let's keep in mind that any multistep synthesis is possible via several routes ❗Questions ❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Chemical synthesis . Wikipedia. https://en.wikipedia.org/wiki/Chemi...
Read more

How to Predict where an Electrophilic Aromatic Substitution May Occur in a Ring – Part 8

Image
An organic reaction in which an atom attached to an aromatic system (usually hydrogen) is substituted by an electrophile is referred to as  electrophilic aromatic substitution  ( S E Ar  or  EAS ). One of the most important  EASs  is nitration . Let's keep in mind that the presence of an activating group on the ring may complicate nitration. Question: Predict the major product(s) of the following reactions: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image Eerie EAS chemistry❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Electrophilic aromatic substitution . Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution. (2)      Brown, C.; Ford, M.  Higher Level Chemistry , 2nd ed.; Pearson Education: Harlow, Essex, 2014. ‌(3)     Electrophilic aromatic directing gro...
Read more