P1 2 Bonding+Structure Flashcards
describe properties of ionic compounds
- high boiling points - they are giant ionic lattices made of pos+neg ions held together by strong electromagnetic force, requires a lot of energy to break (so ionic substances are brittle)
- conduct electricity when molten or in a solution - ionic compounds contain charged particles, particles become free to move when melted/dissolved as particles in a liquid can flow past each other, this solution is an electrolyte
describe what happens to metals+non-metals in ion formation
- metal atoms lose electrons to form positive ions
- non-metal atoms gain electrons to form negative ions
- electron from metal is lost then gained by non-metal ion by electrostatic force from protons in nucleus
- pos+neg ions are attracted by electromagnetic force to form ionic substance
describe properties of simple molecular substances/ small molecules
hydrogen, water, methane
* all atoms have full outer shells so substances cannot chemically bond with other atoms
* weak intermolecular forces so have low boiling points
* cannot conduct electricity as atoms have no electric charge+ there are no free electrons as they are shared
* strong covalent bonds between atoms
* larger molecules have higher boiling points
describe properties of giant covalent substances
diamond, graphite, silicon dioxide/silica
* atoms all joined together with covalent bonds
* bonds are strong so substances are hard+ have high boiling points
* cannot conduct electricity as no free electrons (except graphite)
describe the bonding in metals
- giant ionic lattice of positive metal ions attracted to delocalised electrons
- strong electrostatic force between electrons+ions so have high melting points
- metals are malleable as layers of ions can slide over one another
- conduct electricity+heat as contains delocalised electrons (are free to move+ carry charge)
describe properties of metal alloys
- mixture of elements where at least one element is a metal
- substances are hard+brittle as elements have different sized atoms - this disturbs the layers+ particles cannot easily slide past each other
- pure metals are mixed with other elements to make substances harder for other uses
name metal alloys+ their composition (2)
- brass - copper, zinc
- stainless steel - iron, carbon, chromium
describe 4 limitations of the particle model
- particles actually vary in size
- particles are not actually spherical
- particles are not actually solid as atoms contain empty space
- forces between particles are not represented
name 2 models used to represent giant ionic structures and pros+cons
- ball and stick diagram: shows arrangement of ions, but inaccurate as ions don’t actually have gaps between them
- 3D model: shows arrangement more accurately, but less clear as only outer layers seen
name the allotropes of carbon (4)
- diamond (four bonds)
- graphite (three bonds)
- graphene (three bonds)
- fullerenes: buckminsterfullerene C60, carbon nanotube (three bonds)
describe properties of diamond (4)
- giant covalent structure
- allotrope of carbon
- each carbon atom is held in place by four strong covalent bonds - there are no free electrons so cannot conduct electricity
- strong bonds so has high melting point
- substance is hard due to rigid lattice structure+ bonds
describe properties of graphite (4)
- giant covalent structure
- allotrope of carbon
- strong covalent bonds between atoms arranged in layers - high melting point (but is lower than diamond)
- carbon atoms joined by three bonds - delocalised electrons between layers can conduct electricity - used in electrodes
- has weaker forces between layers so atoms can slide past each other - substance is soft+ slippery - used as a lubricant
describe properties of graphene (4)
- giant covalent structure
- allotrope of carbon
- a single layer of graphite
- strong covalent bonds between atoms - substance is strong, used to make composite materials stronger
- only one atom thick - transparent, used for touchscreen devices
- carbon atoms joined by three bonds - delocalised electrons - conducts electricity
describe properties->uses of fullerenes (5)
buckminsterfullerene* (sphere), carbon nanotube (tube)
* giant covalent structures - hexagonal rings of carbon atoms
* hollow shapes - allow drug molecules to be carried around body - used in medicines
* high tensile strength - used to reinforce materials (eg. tennis rackets)
* high electrical conductivity - used in electrical circuits
* large surface area - help make catalysts
describe properties of polymers
- large molecules (made from smaller molecules/ monomers) with atoms joined by strong covalent bonds
- strong intermolecular forces due to their size so have higher melting points than simple molecular substances
- solids at room temp
- bond diagram shortened into brackets with a number at bottom right corner
