X-ray diffraction by crystals, Types of crystals and Amorphous solids

Question 1

refers to the scattering of X-rays by the units of a crystalline solid. The patterns produced by scattering or diffraction are used to deduce the
particle arrangement in the solid lattice.

Answer 1

X-ray diffraction

Question 2

basically tells us the relative electron densities at various locations in a molecule.

Answer 2

electron-density contour map

Question 3

TYPES OF CRYSTALS

Answer 3

The classification of
any crystal has four types: ionic, covalent, molecular or metallic.

Question 4

There are two important characteristics of ionic crystals and they
are as follows:

Answer 4

(1) They are composed of charged species and
(2) anions and cations are generally quite different in size.

Question 5

The_______of the ions must be known because it is helpful in
understanding the structure and stability of these compounds.

Answer 5

radii

Question 6

Covalent crystals exists when atoms are held together in an
extensive three-dimensional network by covalent bonds. Examples
are the two allotropes of carbon: diamond and graphite.

Answer 6

COVALENT CRYSTALS

Question 7

is considered as a good conductor of electricity in
directions along the planes of carbon atoms. This is because
electrons are free to move around in this extensively delocalized
molecular orbital.

Answer 7

Graphite

Question 8

MOLECULAR CRYSTALS

Answer 8

The lattice points in a molecular crystal are occupied by
molecules which has van der Waals forces and/or hydrogen
bonding.

Question 9

The molecules in a ________ (except for ice) are packed
together as closely as their size and shape allow.

Answer 9

molecular crystals