Metals Chapter 4 Flashcards
Properties of metals
- high boiling points
- good conductors of electricity in solid and liquid states
- malleability and ductilty
- high densities
- good conductors of heat
- lustrous appearances
- Low electronegativities
- low ionisation energies
- react by losing electrons
Differneces between transition and main group metals
- transition metals are harder
- transition metals are more dense
- transition metals have higher melting points
- some transition metals have strong magnetic properties
- transition metal compounds brightly coloured
- less reactive
Why are metals lustrous
metals are lustrous due to the presence of free electons in the lattice → they reflect light of all wavelegnths and appear shiny
Mettallic bodning model (basics)
- charged particles are free to move and conduct electricty
- strong forces of attraction between atoms throughout material
- some electrons are easily removed
Mettallic bodning model (Detailed)
- positive ions are arranged in closely packed strucure known as a three dimensional network of postive ions → these ions are in fixed positions
- negatively charged electrons move freely throughout the lattice in a “sea” of delocalised electrons → these are called delocalised electrons coz belong to the lattice as a whole, yet are allowed to move freely
- the delocalised electrons come from the outer valence shells, the inner shell electrons are not moving and are held firmly with the cations
- Positive cations are held in place by the electrostatic forces of attraction between cations and delocaised electrons. This attraction extends through the lattice and is called mettalic bonding
Limitations of mettalic bonding model
Fails to include
- range of melting points, hardness and densities of differnet materials
- differences in electrical conductivites of metals
- magnetic nature of metals such as cobalt, iron and nickel
Which is more reactive main group metals or transition metals
transition metals are less reactive than main group metals
Describe the reactivity trend of metals in water and outline why they exist
- Going down a group, the reacitivty of a metal increases
- The reactiviy of metals in water increases down the a group and decreases across the period left to right → elemetns in bottom left are most reactive
They exist because ->
- To react atoms must form positive ions
- atoms with largest atomic radii have lowest ionisation energy and thus become ions quickly
How can a metal be modified
- through alloy production
- by heat treatment
- by formation of nanoparticles
What is an alloy
An alloy is a mixture of a mettalic element with other elements
What does heat treatment do to metals
changes size and arrangement of crystals in metals
Describe the two types of alloys
With Diagrams
Interstitial alloy → A small proportion of the element with significantly smaller atoms is added to a metal
Substitutional alloy → atoms of elements added to replace iron cations are called substitutional alloys
Describe the types of crystal structure altering
- Work hardening
- hammering causes crystals to rearrange as they are pushed and deformed
- hammering can result in harder crystals as they are flattened out and pushed closer together
- Heat treatment
- Heating and cooling can alter physical properties of metals
- annealing, quenching and tempering three main types of heat treatment
Describe the structure of particles in a metal
With a Diagram
Each crystal of metals is a continuous arrangement of cations surrounded by a sea of delocalised electrons → however the arrangement of individual crystals in relation to one another is random.
What determines a metal’s brittleness or malleability?
A metals behaviour (malleability + brittleness) depends on size and arrangement of crystals → smaller crystals result in harder metals ans there is not much movement of layers, smaller areas also have less areas of disruption so they will be more brittle as well
