Chemical bonding and language

what is covalent bonding

electrostatic attraction between the protons in the nucleus and the shared pair of electrons

what is ionic bonding

electrostatic attraction between the cation and anion formed by the transfer of electrons from a metal to a non-metal

what is metallic bonding

the electrostatic attraction between metal ions, arranged in a lattice structure and the free-floating electrons around them

why can ionic compounds only conduct electricity in molten form

• as a solid —> ions are bonded in a lattice

• electrons aren’t free to move

why are metals malleable and ductile

layers of metals ions can easily slide over each other without breaking the bonds —> the electrostatic attraction is strong

why can metals conduct electricity

sea of delocalized electrons that are free to move when a voltage is applied

structure of silica (SiO2)

• each silicon atom is bonded to four oxygen atoms

• forms similar shape as diamond

properties of metalloids

• solids at room temp

• some have metallic luster

• brittle

• intermediate electrical conductivity

• moderate densities

examples of metalloids

• boron

• silicon

what is an alloy

mixture of a metal with other metals or carbon designed to improve its properties e.g. strength or resistance to corrosion

how are an alloy’s properties different to the parent metal

• harder

• different elements in the alloys = different size therefore regular lattice arrangement broken

• this makes it more difficult for the ions to slide over each other

uses for copper and suitability

• electrical wires - very good conductor of electricity and ductile

• pots + pans - very good conductor of heat, very unreactive, malleable

• water pipes - unreactive to hot or cold water and malleable

• surfaces in hospitals - antimicrobial properties

different types of steel

• mild steel - iron + 0.25% carbon

• high-carbon steel - iron + 0.6-1.2% carbon + small amount of manganese

• stainless steel - iron + chromium + nickel

uses of mild steel and suitability

• machinery - increased hardness and strength

• car bodies - malleable and ductile

define malleable

can be easily hammered into various shapes

define ductile

can be easily drawn into wires

uses of high-carbon steel

• cutting tools

  • harder

  • more resistant to wear than mild steel

  • BUT more brittle

define brittle

breaks or shatters more easily when a force is applied and doesn’t bend and stretch

uses of stainless steel

• sinks

• saucepans

• knives

• forks

• gardening tools

• chemical industries e.g. brewing and dairy where corrosive resistant is essential - chromium = strong layer of oxide + protects iron

what is volatility

how easily a substance evaporates

structure of diamond

• each carbon atom bonds with 4 atoms

• max number of bonds made

structure of graphite

• each carbon atom bonds with 3 carbon atoms

• layers slide over each other

• sea of delocalised electrons

fullerene (C60)

• made of 60 carbon atoms (or more)

• carbon atoms for pentagons and hexagons

what are the three allotropes of carbon

• diamond

• graphite

• fullerene

what are allotropes

a different form of the same element in the same physical state where atoms are arranged in a different structure

properties of diamond and why

• very hard

• high melting point

• not a conductor

strong covalent bonds throughout and NO free electrons

properties of graphite and why

• soft/slippery

• conducts electricity

• high melting point

layers slide over each other + sea of delocalised electrons are free to move when voltage is applied

properties of fullerene and why

• soft

• low melting point (comparably)

• conducts SOME electricity

molecules held by weak forces + electrons move WITHIN molecules but not BETWEEN

properties of silica (silicon dioxide) and why

• very high MP - lots of strong covalent bonds that need energy to break

• hard

• insoluble - covalent bonds are too strong to be taken over by water

• doesn’t conduct electricity - no free moving electrons or ions