TEST 1 Flashcards
Ionic bonding can be thought of as electron exchange, why?
Ionic bonding happens between two elements with high difference in electronegativity. The stronger element will take the electron from the weaker element.
What is the △EN for Ionic bonding?
> =1.7
Why is covalent bonding thought of as electron sharing?
Covalent bonding happens between two elements with low difference in electronegativity. The two particles will share electrons with each other to lower their potential energy.
What is the △EN for covalent bonding?
=< 1.7
What are dipole dipole interactions?
attraction between the polar sides of a molecule
Where are van der waals forces found?
Almost all organic liquids, solids, and gases; between chains in polymers
What is van der walls force?
attraction because of temporary dipoles between particles
Why do atoms bond?
Because it lowers energy
What happens at equilibrium separation r?
Energy (x) is a minimum and net force is 0
When is Force attractive between two atoms
when r is greater than equilibirum
When is force repulsive at equilibrium?
when r is smaller than equilibrium
what is the E at equilibrium distance r?
the atom-atom bond energy
What property can be derived from equilirbium distance r?
bond length
What property can be derived from the E at equilibrium distance R
Bond energy
What increases if E at equilibrium distance R increases?
Melting point
Do amorphous materials have higher or lower energies than crystalline materials
higher
what is a coordination number for lattice?
Number of nearest neighbors
What is a close packed plane?
Atomic planes with highest density
What is a close packed direction?
Direction where atoms touch
SC
coord#
Atom/cell
CP direction
CP plane
Lattice constant v radius
atoms in unit cell: 1
coord#: 6
Atom/cell: 1
CP direction: <100> (edge)
CP plane: {100}
Lattice constant v radius: a=2R
BCC
coord#
Atom/cell
CP direction
CP plane
Lattice constant v radius
atoms in unit cell: 1
coord#: 8
Atom/cell: 2
CP direction: <111>
CP plane: {110}
Lattice constant v radius: √3 a= 4 R
FCC
coord#
Atom/cell
CP direction
CP plane
Lattice constant v radius
atoms in unit cell: 1
coord#: 12
Atom/cell: 4
CP direction: <110>
CP plane: {111}
Lattice constant v radius: √2 a= 4 R
What is atomic packing factor?
(Volume of all atoms in unit cell)/ volume of unit cell
What is the radius ratio?
Smaller radius/ bigger radius
