Metallic Bonding Flashcards
Describe high tensile strength?
Highly resistant to the stresses of being stretched or drawn out and don’t break easily.
What are metallic lattice structures?
Array of cations surrounded by a sea of delocalised electrons, that holds the lattice together.
What is metallic bonding
WHen metallic atoms combine to form a metallic lattice. Attraction between the cationic lattice and the delocalised electrons.
Why is metal lustre?
Mobile electrons in lattice reflect light
Why do metals conduct heat?
Electrons gain kinetic energy really quickly and cause they can move freely they transfer it by bumping into each other to other bits of metal.
Why metals dense?
Metallic lattices are closely packed
Why high b.p and hard? metals
strong metallic bonding
THE MORE OUTER SHELL ELECTRONS THE STRONGER THE BOND AND HARDER THE METAL IS
Why metals conduct electricity?
Moving charged particles move to positive end of electric current
Why malleable and ductile are metals?
Metallic bonds are non directional so the layers of cations can move past each other. Metal nature doesnt change. :)
What is an alloy?
Metal that has been mixed when molten with other metals or some non metals
What is the process of making an alloy called?
Alloying
What is the term carat?
Ratio of precious metal to base metal in an alloy.
Out of 24, so say 18 carat gold is 18/24 (75%) Gold and 25% something else
What are the tyoes of alloys? Outline what they are?
Interstitial and Substitutional.
Interstitial: The atomic size of the metals differs greatly, small atoms fit into the spaces between the larger atoms.
Subsitutional: Atoms used are about the same size so they can replace each other in the metal crystals.
What is an eg of Substitutional alloy?
Sterling silver
Eg of interstitial alloy
Steel ( Iron and carbon)
What are a few things to note about s block metals?
Very reactive Low density (not many outer shell electrons) Usually form white compounds Light doesnt exist elementally
P Block metal notes?
Good conductors, resistant to corrosion
eg. Lead, Al( creates layer of Al2O3 to not rust)
Properties of D block metals?
Form colourful compounds Some are magnets(iron cobalt and nickel) Most are used as alloys Good catalysts eg copper iron cobalt
Which metals are magnets?
Cobalt Nickel and Iron
Whats wrong with the lattice model?
Doesnt explain magnetism, density or malleability
Outline the principles of the ball bearing model
Metals form perfect close packed grains. The Boundaries between the grains in the metal are called grain boundaries.
the larger the grains in a metal the more easily it bends (less dislocations)
The smaller the grains the more dislocations making it hard to bend
What happens when a metal bends?
Atoms slide over each other. The more easily it slides the more easily it bends
What is work hardening?
Bending or hammering cold metals
Causes the crystals to be smaller, so harder to bend but more brittle
What is annealing?
What does the metal then have?
Heat until red hot then cool slowly
Large crystals
What does annealing cause?
metal is softer
restores ductility to work hardened stuff
What is quenching? What does it cause?
Heat until red hot then cool quickly in cool water
Small crystals
What does quenching cause??
Hard but brittle metal.
Horseshoes
What does tempering do? What is it?
Quenched metal are heated at a slightly lower temp then cooled slowly
Reduces brittleness and retains hardness
Use of tempering>
Axes, and wood carving tools
What is a big problem with metals>
Corrosion
What is surface protection. Give examples
Surface protection aims to prevent air and water from coming into contact with metal, so it doesnt rust
Eg: plastic, paint, grease (machinery)
What are the two types of metal coatings?
Noble and sacrificial
what is noble coating?
Coating of a metal that is less reactive than it, as a cover.
Scratching it means there is corrosion though so it is used generally where there isnt going to be any scratching
What is sacrificial coating?
Coating of metal that is more reactive than it. If it breaks, an electrochemical cell is formed and then that corrodes leaving the metal protected.
Eg zinc forms zinc carbonate on top of steel protecting it
What is a metal that has been sacrificially coated called?
Galvanised….
What happens when a metal and oxygen react?
Forms metal oxide
What happens when a metal and water reacts?
Metal hydroxide and hydrogen
What happens when a metal and acid reacts?
ionic salt and hydrogen produced.
What is something to note about metallic nanomaterials
How does it affects its properties?
- Reactivity is influenced by size of its particles
- High surface area to volume ratio of nano particles increases reactivity and catalytic ability due to greater contact with reactant stuff
