Iron exhibits bcc structure at room temperature. Above 900 °C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900 °C is:

(Molar mass and atomic radii of iron remain constant with temperature) 

1. $\frac{\sqrt{3}}{\sqrt{2}}$

2. $\frac{4\sqrt{3}}{3\sqrt{2}}$

3. $\frac{3\sqrt{3}}{4\sqrt{2}}$

4. $\frac{1}{2}$

The incorrect statement among the following is -

In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion (Ca²⁺) and fluoride ion (F^-) are:

1. 4 and 2

2. 6 and 6

3. 8 and 4

4. 4 and 8