Solids
Materials on Earth are crystals.
Crystals are arrays of atoms.
X-Rays confirm that crystals are three dimensional arrangements of atoms.
The atoms are very close together.
They’re the same distance apart as X-ray wavelengths.
A beam of X-rays directed on a crystal gets diffracted into a characteristic pattern.
This pattern can be made visible on a photographic film.
The pattern is a diffraction pattern.
The film shows that crystals are mosaics of atoms located in regular lattices.
Iron, copper, gold → simple crystal structures
Tin, cobalt → slightly more complex structures
All metals have many crystals.
Each crystal has the same regular lattice.
Each is slightly inclined to the crystal nearby.
When metal surface is etched, the crystals can be seen.
Etched → cleaned with acid
Crystal structures can be seen:
On the surface of galvanized iron
On brass doorknobs that get etched with perspiration from hands
There’s a formula that shows how X-rays should scatter from the atomic layers in a crystal.
This formula combines with the analysis of the pattern of spots in a diffraction pattern to find distances between atoms in a crystal.
X-ray diffraction is vital in biological and physical sciences.
Non-crystalline solids are amorphous.
Amorphous → atoms and molecules are distributed randomly.
Particles can wander.
Eg: Rubber, glass, plastic
In all atoms, atoms and ions vibrate in their positions.
Atoms are tied together by electrical bonding forces.
Called atomic bonding.
Types of bonding in solids:
ionic
covalent
metallic
van der Waals (the weakest)
Materials on Earth are crystals.
Crystals are arrays of atoms.
X-Rays confirm that crystals are three dimensional arrangements of atoms.
The atoms are very close together.
They’re the same distance apart as X-ray wavelengths.
A beam of X-rays directed on a crystal gets diffracted into a characteristic pattern.
This pattern can be made visible on a photographic film.
The pattern is a diffraction pattern.
The film shows that crystals are mosaics of atoms located in regular lattices.
Iron, copper, gold → simple crystal structures
Tin, cobalt → slightly more complex structures
All metals have many crystals.
Each crystal has the same regular lattice.
Each is slightly inclined to the crystal nearby.
When metal surface is etched, the crystals can be seen.
Etched → cleaned with acid
Crystal structures can be seen:
On the surface of galvanized iron
On brass doorknobs that get etched with perspiration from hands
There’s a formula that shows how X-rays should scatter from the atomic layers in a crystal.
This formula combines with the analysis of the pattern of spots in a diffraction pattern to find distances between atoms in a crystal.
X-ray diffraction is vital in biological and physical sciences.
Non-crystalline solids are amorphous.
Amorphous → atoms and molecules are distributed randomly.
Particles can wander.
Eg: Rubber, glass, plastic
In all atoms, atoms and ions vibrate in their positions.
Atoms are tied together by electrical bonding forces.
Called atomic bonding.
Types of bonding in solids:
ionic
covalent
metallic
van der Waals (the weakest)
