Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
8.0k views
in JEE by (3.3k points)
edited by

In the fluorite structure , the number of formula units per unit celll is

1 Answer

+2 votes
by (78.5k points)
selected by
 
Best answer

Fluorite Structures 

The Ca+2 ions are arranged in ccp arrangement, i.e. these ions occupy all the corners and the centres of each face of the cube     

The F ions occupy all the tetrahedral holes.     

Since there are two tetrahedral holes for each Ca+2 ion and F- ions occupy all the tetrahedral holes, there will be two F- ions for each Ca+2 ions, thus the stoichiometry of the compound is 1:2.  

Each Ca+2 ion is surrounded by 8F- ions and each F-ions is surrounded by 4Ca+2 ions. The Coordination number of Ca+2 ion is eight and that of F- ion is four, this is called 8:4 Coordination.  

Each unit cell has 4 calcium ions and 8 fluoride ions as explained below          

No. of Ca+2 ions = 8(at corners)×1/8 + 6 (at face centres)´1/2          

No. of F ions = 8 (within the body)×1 = 8          

Thus the number of CaF2 units per unit cell is 4.  

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...