Space Symmetry

1) Indicate the point symmetry of the following molecules.
a) methane (CH4)
b) CH3Cl
c) CH2Cl2
d) benzene
e) chlorobenzene (C6H5Cl)
f) 1,3 dichlorobenzene (C6H4Cl2)
g) 1,2 dichlorobenzene (C6H4Cl2)

2) The Space Group P222(sub1), has two two-fold rotation axes and one two-fold screw axis. Draw the unit cell, and add the general positions. One two-fold lies directly along the a-axis (draw as the vertical axis). The second two-fold is parallel to the b-axis (draw as horizontal) but intersects c at 1/4. The two-fold screw axis lies directly along the c-axis (draw as normal to the page). Draw the unit cell with all the symmetery and general equivalent positions. I have posted an example for space group P2(sub1)2(sub1)2(sub1) here.

3) Define the following terms.
a) Bravis lattice
b) primitive cell
c) lattice point
d) factional coordinate system
e) unit cell
f) Laue Symmetry