Unit 1.5 Flashcards

1
Q

Ionic solids?

A

a lattice of positive and negative ions

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2
Q

What is Nacl co-ordination number?

A

6:6

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3
Q

What does that mean?

A

1 sodium chloride = surrounded by 6 chloride ions
face centred cubic

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4
Q

Face centred cubic?

A

no molecule in middle of cube
ions = on corners of the lattice

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5
Q

What is CsCl coordinaton number?

A

8:8
Cs = lather than the sodium ion
more chlorides can get around it
Body centred

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6
Q

Properties of Ionic solids?

A

Hard but brittle
High melting points
Giant lattice with strong electrostatic forces
soluble in water
Polar and lattice has ions
If enough force = applied, the layers slide over each other and the ions repel each other

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7
Q

What is their electrical conductivity?

A

Poor when solid
but do conduct when molten as the ions = free to move

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8
Q

Covalent?

A

Macromolecules
e.g Carbon + Silicon
They both have allotropes e.g carbon = diamond + graphite

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9
Q

Allotrope def?

A

2 different structures but made of the same element

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10
Q

Each carbon is?

A

covalently bonded to 4 atoms
tetrahedral
very high melting point ( 3600 degrees)
uniformly bonded throughout
bond lengths = the same

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11
Q

Properties of Diamond?

A

used to make drill bits - glass + diamonds
insoluble in water
doesnt conduct electricity because there is no free electrons
( no attraction to the polar molecule)
strength of the bond + the geometric structure ( 300 kj mol-1)

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12
Q

Graphite?

A

also made of carbon
3 covalent bonds
4 electron = delocalised
weak vanderwaals ( 3KJ mol-1) to break
VDW = examples of induced dipole induced dipole

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13
Q

Physical properties of Graphite?

A

Strong bonds
soft + slippery
weak between layers, strong within
forms a lubricant
good conductor of electricity
low density
large amount of space between layers

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14
Q

Use of Graphite?

A

Sports equipment
Light weight

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15
Q

Simple moleculer solids?

A

Covalent bonds within but held by weak molecular
Individually - covalent
Weak VDW

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16
Q

For example?

A

iodine = low MP + low BP
it sublimes
Grey solid to purple vapour
Liquid = red brown
Solid to gas

17
Q

Ice?

A

Hydrogen bonds (30J)
Less dense than water
arranged in 6’s
held further apart
open space in the ring(ice)