topic3🅱️ Flashcards
ionic solid brief
cations and anions held together with strong electrostatic forces of attraction.
high melting and boiling point
hard, brittle
conductive when molten or dissolved in aqueous solution
NaCl eg
what is a binary solid
a solid comprised of 2 different elements
some binary solids can be what
some binary solids can be molecular or covalent network solids
(SiO2)
although some bindery solids can be molecular or covalent network solids,, many binary solids are
IONIC COMPOUNDS
binary ionic solids can be described using what
explained as being based on close packed structure types.
describe binary ionic solids
close packed array of ions of one element
with ions of the other element located in a proportion of the interstitial sites
number of octahedral interstitial sites in CCP // FCC
N
number of atoms in unit cell (based on its contribution)
1/8 x 8 = 1
1/2 x 6 = 3
1 + 3 = 4
SO 4 OCTAHEDRAL INTERSTITIAL
number of tetrahedral interstitial sites in a ccp // fcc
8!!!
2N
based on an atoms contribution
octahedral interstitial sites in a ccp//fcc
between every atom basically!!
a gap that is bonded to 6 diff atoms (when u expand the unit cell)
one in the centre aswell.
squish the unit cell down and imagine where the gaps are 💗
tetrahedral interstitial sites in a ccp // fcc
in each ✝️ face when u look down.
at 1/4 and 3/4 along the z axis
NaCl ,, salt,, sodium chloride brief
ccp structure
all octahedral interstitial sites filled
NaCl in depth
ccp array of Cl- anions ,, with Na+ cations in ALL octahedral holes
CN of both = 6,, octahedral coordination (the number of the OTHER ion in the structure it’s immediately next to)
general rule with size
anions are the larger ones
other materials with NaCl structure
group 1 and halides
NaX
LiX
AgCl
Fluorite,, CaF2 structure type
ccp structure
all tetrahedral sites filled
no octahedral sites filled
Fluorite,,, CaF2 in depth
ccp array of Ca2+ cations with F- anions in all tetrahedral interstitial sites
Cn: Ca2+ is 8 (cubic coordination)
Cn: F- is 4 ( tetrahedral coordination)
ccp array of X with Y in interstitial sites
X is in the ccp array (all vertices and all faces)
Y is in either the octahedral sites,, tetrahedral sites,, or both!!
octa = between every 2
terra = 1 in each window 1/4 and 1/3
other materials adopting CaF2 structure
BaCl2
BaF2
is smt is in a tetrahedral interstitial site,, what is its coordination number
4!!
CN of 8 ,, cubic coordination explanation
like a bcc
with one ion in the middle and 8 diff types of ion in a cube around it
seen in CaF2 fluorite
what is zinc blende (spheralite) a polymorph of
polymorph of Zns
what is zinc blende // spheralite a polymorph of
ZnS
describe zinc blende // spheralite (ZnS) briefly
based on ccp
1/2 tetrahedral holes are filled by Zn2+ ions
full exp of zinc blende // spheralite
ccp array of S- anions with Zn2+ cations in 1/2 the tetrahedral holes ( 2 at 1/4 and 2 at 3/4)
S- cn = 4,, tetrahedral geometry
Zn2+ cn = 4,, tetrahedral geometry
CuF CuBr CuCl
describe cadmium chloride briefly,, CdCl2
ccp array
Cd2+ fill half the octahedral holes
Cl- take the ccp array (fcc)
describe cadmium chloride in detail
ccp array of Cl- ions with Cd2+ cations filling half the octahedral holes
Cl- cn = 3,, trigonal pyramidal coordination
Cd2+ cn = 6,, octahedral coordination
MnCl2
FeCl2
describe nickel arsenide briefly
NiAs
Ni 2+
As 2-
HCP array of As with Ni in all octahedral sites
describe nickel arsenide fully
Ni 2+. As 2-
hcp array of As 2-
Ni 2+ in all octahedral holes
As in 0,1 and 1/2
Ni in 1/4 and 3/4
CN = 6 for both,, octahedral
briefly describe wurzite
ZnS
Zn 2+
S 2-
hcp array of S,, Zn in 1/2 tetrahedral holes
fully describe wurzite
ZnS
S-2
Zn+2
hcp S array at 0,1 and 1/2
Zn 2+ in 1/2 tetra sites,, at 3/8 and 7/8
cn is both 4
describe hcp all octahedral,, how many octahedral sites are there
2 octahedral sites fully in one unit cell.
anion in hcp array: 0,1 and 1/2
cation at 1/4 and 3/4
describe all tetrahedral holes filled for hcp structure
anion in hcp array 0,1 and 1/2
cation where the anions are but at 3/8 and 5/8 on the sides,,,,, and 1/8 and 7/8 in the centre.
describe cadmium iodide fully
hcp array of I-
Cd 2+ cations in half octahedral holes
I- at 0,1 and 1/2
Cd2+ at 1/4 or 3/4
I- : cn = 3
Cd2+ : cn = 6
