chemistry-chemical bonding
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- Created by: Sophie Conway
- Created on: 15-02-14 13:25
name the 4 types of chemical bonding
metallic bonding,ionic bonding,simple molecular/covalent bonding,giant covalent substances
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describe metallic bonds
particles in metal-held together by mb.Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalised electrons.
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how does metallic bonding explain physical properties-bp and mp's?
attraction between the metal ions+delocalised electrons must be overcome to melt or to boil a metal. Some of attractions must be overcome to melt a metal+all must be overcome to boil it.These attractive forces are strong,so metals-high mp+bp
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how does metallic bonding explain physical properties-electric current?
The delocalised electrons are able to move through the metal structure. When a potential difference is applied, they will move together, allowing an electric current to flow through the metal.
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diagram of metallic bonding
x
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describe ionic bonding
Positive and negative ions attract one another and bind together forming a new substance. This is called IB.
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describe the example of ionic bonding;sodium chloride
when react-sodium looses outmost electron+chlorine atom gains an electron. both form ions. sodium becomes positive ion(Na+ bc lost electron)chlorine-negetive(Cl- bc gained electron).
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how does the ionic lattice(held together by strong forces around the ion)model explain the high mp's of ionic compounds?
the + and - ions have strong attractive electrostatic forces between them which needs lots of energy to overcome them.
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how does the ionic lattice(held together by strong forces around the ion)model explain why solid ionic compounds do not conduct electricity?
the + and - ions held in fixed positions within their lattice+not free to move. so no electrical conduction bc no moving charged particles.
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how does the ionic lattice(held together by strong forces around the ion)model explain why when milton or dissolved in water ionic compounds do conduct electricity?
the lattice breaks down on melting or dissolving and ions are free to move and create a electrical current
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how does the ionic lattice(held together by strong forces around the ion)model explain the brittleness of ionic substances
if a stress force is applied to ionic solidmthis shifts the ion layers slightly +layers will jump over each other. ions of same charge are bright side by side and so repel each other.
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describe simple molecular bonding(covalent)
molecules formed from atoms when they share electrons-making covalent bonds.each atoms shartes enough electrons to fill other shell.dot cross diagrams.some atoms form double covalent bonds-each atom shares four electrons in two pairs e.g. co2.
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covalent bonds-explaining physical properties.
solid C substances-low melting points bc little energy is needed to separate the molecules+turn solid to liquid.many c-liquids+gases are room t.covalent bonds between atoms in molecule-very strong.very weak forces between molecules-each is neutral.
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describe giant covalent
diamond and graphite are examples.-have high mp bc all atoms are held together by strong covalent bonds.all consist of caron.carbon has 4 outer e.-needs to share 4 other electrons to get completee outer electron shell.
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describe carbon in diamond-giant covalent
in diamond each carbon atom is connected to 4 other carbon atoms by strong covalent bonds-forming its structure.
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describe carbon in graphite-giant covalent
layers of carbon atoms arranged in hexagonal rings.each carbon atom forms strong covalent bonds with 3 other in same layer.4th electron from each atom joins mobile system of electrons between layers. these free electrons form bonds between layers tha
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explaining physical properties-giant covalent substances-diamond
all 4 outer electrons involved in covalent bonding+rigid giant structure of carbon atoms formed.-gives diamond its extreme hardness+high mp bc a lot of energy is needed to break down lattice.no free electrons to conduct electricity.
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explaining physical properties-giant covalent substances-graphite
bonds between the layers-weak.so has a slippery feel+good lubricating properties.strong covalent bonds within layers-mean mp high.mobile electrons allow graphite to conduct electricity quite well along layers but doesn't conduct electricity across la
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what are carbon nanotubes?
another physical form of carbon.they are molecular scale tubes of rolled up graphite layers.stiffer+stronger than steel+conduct electricity better than copper.
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carbon nanotubes-explaining physical properties.
the covalently bonded hexagonal carbon sheets make carbon nano tubers v strong.free electrons give them high electrical conductivity.
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look in chem book to add
x
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Other cards in this set
Card 2
Front
describe metallic bonds
Back
particles in metal-held together by mb.Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalised electrons.
Card 3
Front
how does metallic bonding explain physical properties-bp and mp's?
Back
Card 4
Front
how does metallic bonding explain physical properties-electric current?
Back
Card 5
Front
diagram of metallic bonding
Back
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