A) MgO has the rock-salt structure. The MgO crystal has a value of 0.514 for the radius ratio. The length of a side of the unit cell for MgO is 4.24 Å.

(i) Draw the structure of this molecule.
(ii) Determine the radii of Mg 2+and O2-, assuming that the O 2-ions are in contact with one another.
(b) Define what is meant by the "coordination number" of a crystal structure.
(c) Determine the coordination number for each of the following crystal structures:
(i) Face-centred cubic (NaCl)
(ii) Body-centred cubic (CsCl)
(iii) Zinc blende (ZnS)

The ozone molecule o3 has a permanent dipole moment of 1.8×10−30 cm. although the molecule is very slightly bent-which is why it has a dipole moment-it can be modeled as a uniform rod of length 2.5×10−10 m with the dipole moment perpendicular to the axis of the rod. suppose an ozone molecule is in a 8000 n/c uniform electric field. in equilibrium, the dipole moment is aligned with the electric field. but if the molecule is rotated by a small angle and released, it will oscillate back and forth in simple harmonic motion.what is the frequency f of oscillation?

The density of the solid phase of a substance is 0.90 g/cm3 and the density of the liquid phase is 1.0 g/cm3. a large increase in pressure will a. lower the freezing point b. raise the freezing point c. lower the boiling point d. raise the triple point e. lower the triple point

Who examines and coordinates the cleanup of polluted sites?