[email protected]

India's First Online IIT-JEE & NEET Coaching Platform - Trusted Since 2006

+91-87964 74404

12 grade chemistry others

What are F-centers in an ionic crystal ?

Aniket Singh

1 Year agoGrade

1 Answer

Askiitians Tutor Team

1 Year ago

In an ionic crystal, F-centers, also known as color centers, are defects that arise when an anion vacancy is created due to the loss of an anion (negatively charged ion) from its lattice site. This creates a localized region of positive charge within the crystal lattice.

The term "F-center" comes from the German word "farbe," meaning color. These defects are often responsible for the coloration of certain crystals. For example, in sodium chloride (NaCl), common table salt, F-centers are responsible for the yellow coloration observed in irradiated or thermally treated crystals.

The color arises because the F-center can absorb photons of specific wavelengths corresponding to the energy difference between electronic states within the crystal lattice. The absorbed energy promotes electrons from the valence band to higher energy levels within the defect, creating a characteristic color in the visible spectrum.

F-centers can significantly influence the optical and electronic properties of ionic crystals, making them important in various applications, including materials science, optoelectronics, and solid-state physics.

is Pradeep Chemistry+Ncert sufficient for all of the theory of Jee Mains Chemistry?

Hi, I’m a self-study JEE 2027 aspirant with a large 11th backlog. Since I don’t think 6–8 hour one-shots are sufficient to cover the full theory + breadth of problem types of a JEE chapter, I’ve shifted from lecture-based preparation to book-based self-study.

I have a problem with using NCERT as my primary chemistry source. In my experience, it is concise and information-heavy, but often lacks detailed explanations, systematic organisation of concepts, and categorisation of problem types. This seems especially problematic for Physical and Organic Chemistry, where I feel that simply reading NCERT may not give enough depth or problem-solving preparation.

So I’m considering this approach:

Pradeep Chemistry → complete the chapter thoroughly from Pradeep → then read NCERT for that chapter → solve JEE Main PYQs/problems.

My main question is:

Is Pradeep + NCERT sufficient as the complete theory source for JEE Main-level Chemistry?

In other words, after thoroughly completing a chapter from Pradeep and then NCERT, can I consider the theory part of that chapter complete for JEE Main, with only PYQs/problem practice remaining?

I’m asking specifically about JEE Main level, not Advanced.

Also, if Pradeep is not sufficient, what specific gap does it leave, and what would you recommend as a better book-based alternative for self-study?

Grade 1212 grade chemistry others

1 Answer Available

Last Activity: 9 Days ago

Which of the following is more acidic in nature?
A. HClO
B. HCl₂O
C. HCl₃O
D. HCl₄O

Grade 1212 grade chemistry others

1 Answer Available

Last Activity: 1 Year ago

Which of the following is not a greenhouse gas?

A. Carbon dioxide

B. Sulphur dioxide

C. Methane

D. Nitrogen

Grade 1212 grade chemistry others

1 Answer Available

Last Activity: 1 Year ago

Which of the following is not an antibiotic?

(A) Morphine

(B) Penicillin

(C) Streptomycin

(D) Chloramphenicol

Grade 1212 grade chemistry others

1 Answer Available

Last Activity: 1 Year ago

Which of the following is not optically active?
A. [Co(en)₃]³⁺
B. [Cr(ox)₃]³⁻
C. cis - [CoCl₂(en)₂]⁺
D. trans - [CoCl₂(en)₂]⁺

Grade 1212 grade chemistry others

1 Answer Available

Last Activity: 1 Year ago

View all Questions