Question

AB has NaCl type structure, if all the atoms touching one of the triad axis is removed, formula of unit cell will be​

Answer 1

Answer:A4B5

Explanation:in triad axis

2corner atom ,1body center is removed

Answer 2

NaCl has face centered cubic structure in which 8 Cl^- ions present at corners and 6 Cl^- ions present at face center of unit cell while 12 Na^+ ions  present at edge-center and one Na^+ ion presents at body center of unit cell.

number of Na^+ atoms in a unit cell = 12 × 1/4 + 1 = 4

number of Cl^- atoms in a unit cell = 8 × 1/8 + 6 × 1/2 = 4

that's why it's molecular formula is NaCl.

same mechanism for AB,

initial time,

number of A atoms in a unit cell = 4

number of B atoms in a unit cell = 4

now, Triad axis, it is also known as cube diagonal. so, each diagonal of AB structure contains 2 corners and a body center. these are now removed.

so, number of A atoms in a unit cell = 3

and number of B atoms in a unit cell = 4 - 2 × 1/8 = 4 - 1/4 = 15/4

so, formula will be $A_3B_{15/4}$ or $A_{4}B_{5}$