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Handout 6 > Atomic solids; molecular solids; ionic solids > Flashcards

Atomic solids; molecular solids; ionic solids Flashcards

1
Q

What are the intermolecular forces which hold atomic solids?

A

dispersion forces (London forces)
- weak forces
- arise from instantaneous dipole at one atom inducing dipole in its neighbor
(thus get synchronized motion of electron in adjacent atoms)

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2
Q

what are the examples of atomic solids?

A

G18

Ar crystallizes at very low T in a cubic closest packed structure

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3
Q

What are the intermolecular forces acting on molecular solids?

A

dipole-dipole, dispersion, H-bonding

- still relatively weak

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4
Q

what is the effect of the varied intermolecular forces acting on molecular solids?

A

wide range of physical properties

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5
Q

what are the lattice points of a molecular solid occupied by?

A

molecules

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6
Q

what does methane crystallize into?

A

in face centered cubic structure

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7
Q

why do molecular solids have lower mp than ionic, network covalent and metallic solids?

A

due to their weak intermolecular forces

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8
Q

true or false; the particles of ionic solids have charges

A

true

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9
Q

true or false; the inter-particle forces are much greater in ionic solids

A

true

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10
Q

why is the inter-particle forces in ionic solids much greater than molecular solids?

A

they maximize their attraction; cations are surrounded by as many anions as possible and vice versa

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11
Q

where do the smaller ions lie in the packing of ionic solids?

A

in the spaces (holes) formed by close packed larger ions

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12
Q

true or false; the unit cell has the same cation: anion ratio as the empirical formula

A

true

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13
Q

what is the most common ratio that crystal structures adopt?

A

1:1 cation:anion ratio cubic closest packing eg. NaCl and ZnS

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14
Q

In NaCl structure; what type of array does the Cl- ions make?

A

cubic closed packed

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15
Q

in NaCl where do the smaller sodium ions fit into?

A

the holes or spaces within the lattice

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16
Q

What type of arrangement does the NaCl adopt?

A

face centred

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17
Q

how many Cl- ions surround each Na+ ions? (vice versa) CN

A

6

18
Q

what holes are the Na+ ions filling?

A

octahedral of the fcc lattice of the Cl- ions

19
Q

How many Cl- ions in the NaCl unit cell?

A

4

20
Q

how many Na+ ions in the NaCl unit cell

A

4

21
Q

where is the NaCl structure mostly found in?

A

G1 halides and hydrides
G2 oxides and sulfides
most AgX

22
Q

What is Zinc blende?

A

ZnS

23
Q

What type of array is ZnS packed?

A

cubic close packed array of S(2-) ions with the cations Zn(2+)

24
Q

what holes are the Zn(2+) occupying in the S(2-) lattice? (vice versa)

A

half of the tetrahedral holes

25
Q

how many S(2-) surround each Zn(2+) ions (vice versa) CN

A

4

26
Q

how many Zn(2+) ions in a ZnS unit cell?

A

4

27
Q

how many S(2-) ion in a ZnS unit cell

A

4

28
Q

what is the ion ratio of ZnS

A

1:1

29
Q

true or false; only 4 of 8 tetrahedral holes in the fcc unit cell are filled by Zn(2+)

A

true

30
Q

What other compounds adopt the ZnS structure

A

Cu(i) halides, CdS, AgI

31
Q

What determines the type of structure other compounds will adopt

A

the sizes of the cation:anion ratio

32
Q

true or false; the space available in an octahedral hole is much larger than in a tetrahedral hole in a cubic close packed array

A

true

33
Q

what radius ratio is needed for cation:anion for ZnS to be adopted?

A

> 414

34
Q

radius ratio cation:anion for NaCl structure

A

> 414 but no more than 732 (between 414 and 732)

35
Q

cation: anion radius ratio for CsCl structure; interpenetrating cubic arrays (most stable)

A

<732

36
Q

what is anion to cation ratio of CsCl

A

0.92

37
Q

what array forms the CsCl structure

A

cubic array of Cl- ion with Cs+ ions

38
Q

which holes are Cs+ ions placed in

A

cubic holes

39
Q

what is the lattice of CsCl constructed form?

A

cubic Cl-

40
Q

what is the CN (coordination number) of cation and anion of CsCl

A

8

41
Q

true or false; anions are generally larger than cations

A

true

Handout 6 (9 decks)

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