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Chemistry > Chapter Four > Flashcards

Chapter Four Flashcards

Metals

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1
Q

Properties of metals

A
  • Range of melting points and relatively high boiling point
  • Conductors of electricity
  • Generally high densities
  • Malleable
  • Ductile
  • Lustrous
  • High tensile strength
  • Low ionisation energies and electronegativities
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2
Q

What type of ions do metals form

A

Metals usually form cations as they lose their valence electrons to meet the octet rule

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3
Q

What are transition metals used for

A
  • Bridges
  • Cans
  • Railway lines
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4
Q

Properties of transition metals

A
  • Harder
  • Higher densities
  • Higher melting points
  • Some have strong magnetic properties
  • Greater core charge
  • Atoms are smaller
  • Stronger bonds
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5
Q

Iron

A
  • Brittle and corrodes easily
  • Mixed with carbon and other transition metals to make alloys such as steel
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6
Q

Lattice

A

Tightly packed arrangement

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7
Q

What do electrons do in metallic bonding

A

The electrons delocalise to form a ‘sea’ of electrons throughout the entire metallic structure which are strongly attracted to the metal cations

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8
Q

What does the metallic bonding model include

A
  • Charged particles that are free to move andd conduct electricity
  • Strong fforces of attraction between atoms throughout the metal structure
  • Some electrons that are relatively easily removed
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9
Q

How are cations held in the lattice

A

Through strong electrostatic attraction between the cations and the electrons > it extends throughout the lattice

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10
Q

Why are metals dense

A

Cations are closely packed together

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11
Q

What is metallic bonding

A

The attraction between the positively charged ions and the delocalised electrons

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12
Q

Why are metals lustrous

A

Free electrons allow the metal to reflect light of all wavelengths and appear shiny

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13
Q

Why are metals good conductors of heat

A

When the metal is heated the delocalised electrons gain energy and vibrate more rapidly, by bumping into neighbouring electrons it allows for the rapid transmittance of energy throughout the lattice

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14
Q

Limitations of the metallic bonding model

A
  • Range of melting points, hardness and densities of different metals
  • Differences in electrical conductivities of metals
  • Magnetic nature of some metals
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15
Q

Reactivity with acids

A
  • Metals are normally more reactive with acids than water > the reactions tend to be more energetic
  • E.G > Magnesium + hydrochloric acid -> magnesium chloride + hydrogen gas
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16
Q

Reactivity with water

A
  • Metals in group one are more reactive with water than metals in group two
  • Going down the group reactivity increases
17
Q

Reactivity with oxygen

A
  • Group 1 react rapidly
  • Group 2 reacts just not as rapidly and heat is usually required
  • Transition metals are less reactive than these two groups
  • E.G > sodium + oxygen -> sodium oxide
18
Q

Why does reactivity change

A

Due to the relative attractions of valence electrons to the nucleus of atoms

19
Q

Ways of modifying metals

A
  • Alloy production
  • Heat treatment
  • Formation of nano-sized structures
20
Q

Alloys

A
  • Metals are mixed with small amounts of another substance- usually a metal or carbon
  • They are melted together, mixed and then allowed to cool
  • Generally harder and melts at lower temperatures than pure metals
21
Q

Interstitial alloys

A

When a small proportion of an element with significantly smaller atoms are added to a metal and the small atoms sit in the interstitial spaces between the metal cations

22
Q

Substitutional alloy

A
  • When elements with bigger atoms are added, they replace some of the cations in the lattice
  • Similar chemical properties and form cations of a similar size to the main metal
23
Q

What do malleability and brittleness depend on

A

Malleability and brittleness depends on size and arrangement of the crystals

24
Q

Work hardening

A
  • Hammering or working cold metals causes the crystals to rearrange as they are pushed and deformed
  • Results in hardening of the metal as the crystals are flattened out and pushed closer together
25
Q

Heat treatment

A
  • When heated above critical temperatures individual crystals merge and re-form when allowed to cool
  • The rate of cooling determines the size of crystals
26
Q

Metallic nanomaterials

A
  • Particles
  • Rods
  • Wires
  • Tubes
27
Q

Metallic nanoparticles

A

Nanoparticles that contain only 100 or so atoms have properties in between those of metals and non-metals > different optical properties and more sensitive to heat

28
Q

Nanorods

A

Nanoscale rods > display technologies and microelectronics (solar cells + mobile phones)

29
Q

Nanowire

A
  • A nano sized wire
  • Longer than nanorods
  • Catalysts, electronics
30
Q

Why are nanomaterials good for use

A
  • Have unique electrical. catalytic, magnetic, mechanical, thermal and imaging characteristics
  • Attractive for use in the medical, pharmaceutical, electronic and engineering sectors
31
Q

Delocalised

A

Detached or removed from a particular place or location

Chemistry (11 decks)

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