Transition Metals, Corrosion, Alloys, Electroplating Flashcards
What are the general physical properties of transition metals?
- Malleable
- Ductile (can be stretched out)
- Shiny when polished
- Good electricity conductors
What are the general chemical properties of transition metals?
- Transition metal compounds are usually coloured
- Transition metals and their compounds show catalytic activity
How to transition metals compare to metals in groups 1 and 2?
- High melting points
- High densities
How does corrosion occur?
Metal continues to oxidise and so becomes weaker over time
How are metal oxides formed?
Metal reacts with oxygen (oxidises)
What is rusting?
Corrosion of iron or steel (steel is mostly iron) in the presence of oxygen and water
How does rusting of Iron occur?
Iron reacts with oxygen and water
How can rusting be prevented? (not including sacrificial protection)
Air is kept away: Stored in an unreactive atmosphere of nitrogen or argon
Water is kept away: Desiccant powder absorbs water vapour
Air and water is kept away: Painting, coating with plastic, oiling, greasing
Explain Sacrificial Protection
- Attach a piece of zinc or magnesium to the metal
- They oxidise more easily than iron/steel, so the oxygen reacts with them instead
- Protection continues until the sacrificial metal corrodes away
What’s the equation for rusting iron?
Iron + oxygen + water —> Hydrated Iron(III) Oxide
What’s Electroplating?
The process of coating the surface of a metal with a thin layer of another metal
Why are metal objects Electroplated?
- Looks nice whilst being cheaper (aesthetics)
- Improves a metal object’s ability to resist corrosion
How is electroplating carried out?
At the anode: Oxidation (loss of electrons) to become ions
At the cathode (object): Reduction (gain of electrons) to become atoms
What are some common examples of electroplating?
Chromium is a transition metal that resists corrosion: Vehicle/boat parts are ‘chrome plated’
Silver and gold are expensive: They are electroplated onto cheaper base metals e.g. copper and nickel. This produces attractive jewellery that is cheaper than solid silver/gold
What’s an Alloy?
A mixture of a metal element with one or more other elements
Why is iron alloyed with other metals?
Pure iron is too soft for everyday use
Are alloys stronger than the metal they contain? - explain why
Yes
In pure metals, the atoms are the same size and arranged regularly in layers, so, they move past each other when force is applied (so they are malleable and ductile)
In an alloy, the atoms of the other elements present may be different sizes and distort the regular structure, making it harder for the layers to slide past each other
What are the uses for aluminium, copper and gold?
What are alloy steels?
Alloy steels are made when other elements are added to iron
Explain the uses and benefits of Stainless Steels (and what they are)
Type of alloy steel containing chromium that resists rusting. When this reacts with oxygen in the air, it forms a layer of chromium oxide that stops air and water from reaching the metal. It is also transparent. If the metal is scratched, more chromium reacts to replace the layer.
