Antifluorite Na2O has a unit cell edge of 555 pm. Taking sqrt3=1.732, the shortest Na+-Na+ distance and the shortest Na+-O^2- distance (in pm) are respectively

JEE Advanced levelSingle correct optionDifficulty 3 of 3ss142

Antifluorite $Na X_{2} O$ has a unit cell edge of $555 pm$ . Taking $3 = 1.732$ , the shortest $Na X^{+}$ - $Na X^{+}$ distance and the shortest $Na X^{+}$ - $O X^{2 -}$ distance (in pm) are respectively

Na X^{+}

ions occupy tetrahedral positions

(\frac{1}{4}, \frac{1}{4}, \frac{1}{4})

, so the nearest two are

a /2 = 277.5 pm

apart. The

Na X^{+}

O X^{2 -}

contact is along the quarter body diagonal:

3 a /4 = 240.3 pm