Gold adopts a face-centered cubic structure with a unit celledge of 4.08 Å (Figure 12.11). How many gold atoms arethere in a sphere that is 20 nm in diameter? Recall that thevolume of a sphere is 43pr3

7.21 In a crystal with a face-centred cubic structure, the basic cell can be taken as a cube of edge a with its centre at the origin of coordinates and its edges parallel to the Cartesian coordinate axes; atoms are sited at the eight corners and at the centre of each face. However, other basic cells are possible. One is the rhomboid shown in figure 7.17, which has the three vectors b, c and d as edges. (a) Show that the volume of the rhomboid is one-quarter that of the cube. (b) Show that the angles between pairs of edges of the rhomboid are 60° and that the corresponding angles between pairs of edges of the rhomboid defined by the reciprocal vectors to b, c, d are each 109.5°. (This rhomboid can be used as the basic cell of a body-centred cubic structure, more easily visualised as a cube with an atom at each corner and one at its centre.)

Question 19 If the area of a Nitrogen molecule is 15 Angstrom2, approximately how many moles of N2 would give monolayer coverage on a sample with a 50m² surface area. 0.5 x 10 moles 0.5 x 103 moles 0.5 x 109 moles 5 moles 0 0.5 moles

(1) For the cubit unit cell shown below, a. How many atoms are there within in the cell? b. What is the name of the lattice characterized by this unit cell? Explain your answer.