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inorganic sem 2 > topic 2🅱️ > Flashcards

topic 2🅱️ Flashcards

1
Q

coordination number

A

number of atoms or ions immediately surrounding a central atom in a complex or crystal

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2
Q

coordination number of ccp or fcc and hcp structures

A

12!!

3 above, 3 below, 6 on the same level

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3
Q

bcc coordination number

A

8
not closed packed
cubic geometry

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4
Q

primitive cubic structure coordination number

A

6
octahedral geometry.
the atom is part of a few unit cells

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5
Q

what’s an interstitial site

A

gaps between closed packed structures

atoms,, even when closely packed,, have gaps between them,, they aren’t packed with 100% efficacy

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6
Q

can interstitial sites be occupied by other atoms

A

yes!!!

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7
Q

most efficient way of packing

A

being closely packed
reduces the interstitial sites between them.

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8
Q

how can interstitial sites be categorised

A

categorised by their geometry

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9
Q

2 close packed type of interstitial site
HCP + CCP can have which interstitial sites

A
  • octahedral site
  • tetrahedral site
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10
Q

octahedral interstitial site

A

between 2 triangles above + below.
between 6 atoms

can see all the way through the structure

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11
Q

tetrahedral interstitial site

A
  • between a triangle above + a single atom below
    (can’t see all the way through the structure)

between 4 atoms

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12
Q

amount of octahedral sites in a close packed structure issss

A

‘N’
where N is the amount of atoms in host

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13
Q

number of tetrahedral interstitial sites in a close packed structure

A

2N

N is the number of atoms in a host

tetrahedral: between 4 atoms

double the amount of octahedral sites

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14
Q

how can we draw a unit cell diagram

A
  • space filling diagram
  • ball and stick diagram
  • cell projection diagram
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15
Q

what is a cell projection diagram

A

a 2D diagram of the unit cell,, viewed from above

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16
Q

what is lost when drawing a cell projection diagram

A

info on the Z axis!! aka how tall the unit cell is + where the diff atoms are placed on the z axis

17
Q

how can we show where the atoms are in a cell projection diagram

A

draw the atoms in diff environments :: code them with either 0,1 or 1/2 to show where they’re located

18
Q

when drawing a cell projection diagram,, what must we do

A

look at the diff atom environments
code each different environment
give them a number to show where they are on the Z axis

19
Q

are close packing structures 100% efficient

A

no!! they have interstitial sites aka gaps between atoms in a close packed structure

20
Q

how can we measure how efficient a close packed structure is in terms of packing

A

find the packing efficiency

21
Q

what is the packing efficiency

A

the percent of the structure that is filled by the atoms // ions

22
Q

packing efficiency equation

A

volume of atoms in a unit cell // total volume of the unit cell

x100

23
Q

what must we find to figure out the packing efficiency

A

we must know the volume of the atoms + the volume of the unit cell

24
Q

how do we figure out the total number of atoms in the unit cell

A
  • find how many atoms there are + if they’re on a vertices or a face
  • find their contribution eg: 1/ how many other unit cells they’re present in
  • contribution x total amount of them in ONE unit cell
25
Q

how do we find the total volume of atoms in a unit cell

A
  • u have the total amount of atoms
  • number of atoms x volume of one atom
26
Q

what is the equation for the volume of one atom assuming it has hard sphere behaviour

A

V = 4/3 nr3

n = pi
r = atomic radius

27
Q

how do we find the total volume of the unit cell cell

A

length = 4 radii
use Pythagoras
to find a side (if it’s cubic : a=b=c)
so volume is a3
pythag will give one a 🫶

28
Q

what’s an intensive property

A

a bulk property
they’re independent on the size of the system

density is an example 🫶

29
Q

equation for density

A

density = mass / volume

30
Q

to find the density of the unit cell what to we need

A

the volume of the unit cell

total number of atoms so we can find the total mass of unit cell.

31
Q

what do we multiply the mass by to find the mass of the unit cell

A

not the total amount of atoms.

but the total amount found by their contributions.

32
Q

converting pm into cm

A

x 10-10

33
Q

to convert amu to grams

A

amu / avogadros number

34
Q

unit for density

A

g/cm3

or kg/m3

35
Q

amu to grams

A

divide ➗ by avogadro

36
Q

pm to m

A

x10 ^ -12

37
Q

common density units

A

g/cm3

kg/m3

38
Q

density of unit cell steps

A

density = mass // vol

(mass in amu / avo) x number of atoms in unit cell

vol = volume of unit cell

grams and cm3
kg and m3

mass/volume

inorganic sem 2 (16 decks)

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