Ionic radii of cation A+ and anion B are 102 and 181 pm respectively. These ions are allowed to crystallize into an ionic solid. This crystal has cubic close packing for B. A+ is present in all octahedral voids. The edge length of the unit cell of the crystal AB is________ pm.

(Nearest integer)

<p>Edge length of the unit cell AB = a = 2&nbsp;<math><mrow><mrow><mo> (</mo><mrow><msub><mrow><mi>r</mi></mrow><mrow><mo>+</mo></mrow></msub><mo>+</mo><msub><mrow><mi>r</mi></mrow><mrow><mo>−</mo></mrow></msub></mrow><mo>)</mo></mrow></mrow></math></p><p><math><mrow><mo>∴</mo><mi>a</mi><mo>=</mo><mn>2</mn><mrow><mo> (</mo><mrow><mn>1</mn><mn>0</mn><mn>2</mn><mo>+</mo><mn>1</mn><mn>8</mn><mn>1</mn></mrow><mo>)</mo></mrow><mo>=</mo><mn>2</mn><mrow><mo> (</mo><mrow><mn>2</mn><mn>8</mn><mn>3</mn></mrow><mo>)</mo></mrow><mo>=</mo><mn>5</mn><mn>6</mn><mn>6</mn></mrow></math></p>

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