bonding Flashcards
what are the three types of bonding
metallic -between metals
ionic-between meals and nonmetals
covalent-between nonmetals
what are the 5 properties of metallic bonds
strong
high melting and boiling points
good electrical and thermal
malleable and ductile
3 properties of metallic bonding
extended
Strong – metals cannot easily be broken due to the strong metallic bonds (i.e. the electrostatic attraction between the positive metal ions and the delocalised electrons).
High melting and boiling points – a lot of heat energy is required to break the strong metallic bonds (i.e. the electrostatic attraction between the positive metal ions and the delocalised electrons).
[Higher tier only] The greater the number of outer electrons that the metal has, the higher its melting point. This is due to the increased positive charge on the metal ion and the increased number of electrons that are delocalised, resulting in stronger metallic bonding. For example:
what are the properties of ionic bonding
High melting and boiling points – a lot of heat energy is required to break the strong ionic bonds (i.e. the strong electrostatic forces between the ions).
[Higher tier only] The greater the charge on the ions, the stronger the ionic bonds and, therefore, the higher the melting and boiling points.
Only conduct electricity when molten or dissolved in water – when the compounds are solid, the ions cannot move and so cannot carry electrical energy. However, when molten or dissolved in water, the ions can move and carry electrical energy.
Brittle – ionic compounds break apart easily. When a force is applied to an ionic crystal, the ion layers shift so that ions of the same charge are brought side by side, repel each other and cause the crystal to shatter.
Usually soluble in water – water molecules are slightly charged and are able to break apart the ions in a giant ionic lattice.
covalent bonds
Low melting and boiling points – the covalent bonds holding atoms together within a molecule are strong, but each molecule is attracted to other molecules by very weak intermolecular forces. These intermolecular forces can be overcome with a small amount of heat energy, so simple covalent substances have low melting/boiling points.
Poor conductors of electricity – simple covalent molecules cannot conduct electricity as they do not contain any mobile charged particles (i.e. they do not have free electrons and do not form ions).
Variable solubility in water – the solubility of simple covalent compounds in water varies a lot between substances. For example, sugar is extremely soluble in water whereas petrol is completely insoluble in water.
what is diamond
Diamond is the most stable allotrope of carbon where each carbon atom is covalently bonded to four other carbon atoms in a 3D lattice.
what are the properties fa diamond
Very high melting point – each carbon atom is bonded to four other carbon atoms with strong covalent bonds that need a lot of heat energy to break.
Very hard – again due to the fact that each carbon atom is joined to four other carbon atoms with strong covalent bonds. Uses of diamond related to its hardness include glass cutting, tips of dentists’ drills and tips of other drills such as those used for oil exploration.
Electrical insulator – diamond does not have any free electrons and so cannot conduct electricity.
what is graphite
Graphite is the most common allotrope of carbon where the carbon atoms are covalently bonded to three other carbon atoms and arranged in layers or hexagonal rings.
what are the properties of graphite
Very high melting point – each carbon atom is bonded to three other carbon atoms with strong covalent bonds that require a lot of heat energy to break.
Soft and slippery to the touch – the atoms within each layer are held together by strong covalent bonds but the layers themselves are held together by weak intermolecular forces. This means the layers of carbon atoms can easily slide over each other when a force is applied. Uses related to this property include solid lubricant and pencil ‘lead’.
Good conductor of electricity – the delocalised electrons between the layers can carry electrical energy. Uses related to this property include electrodes for electrolysis (including high temperature electrolysis, such as the extraction of aluminium).
what are fullerenes
Fullerenes are allotropes of carbon in which the atoms form balls or ‘cages’. Fullerenes have delocalised electrons, like graphite, as they are only bonded to three other carbon atoms. The fourth electron is delocalised.
what are fullerenes used for
drug delivery (by trapping drug molecules in the fullerene until released)
use as a lubricant due to the weak intermolecular forces between each fullerene
use as a catalyst due to its extremely large surface ar
waht are nanotubes
Nanotubes are a single layer of graphite (known as a graphene layer) that has been rolled up to form a tube of carbon atoms.
what are the properties of nanotubes
ery strong – each carbon atom is bonded to three other carbon atoms with strong covalent bonds that require a lot of force to break. Uses related to this property include bicycle components, boat hulls and epoxy-resins for bonding high performance components in wind turbines and sports equipment.
Soft and slippery to the touch – the atoms within each tube are held together by strong covalent bonds but the tubes themselves are held together by weak intermolecular forces. This means the tubes of carbon atoms can easily slide over each other when a force is applied. Uses related to this property include solid lubricant.
Very good conductor of electricity – the delocalised electrons within the tube can carry electrical energy, making nanotubes one of the best electrical conductors known. Potential uses related to this property include electrical connections in miniaturised electrical circuits (however, current technology does not allow us to arrange the nanotubes within the circuit properly).
what is graphene
Graphene is the name given to a single layer of carbon atoms by itself, arranged in the same way as in a layer of graphite. Graphene is only 1 atom thick (the thinnest material known to exist) and has a very low density (1 square metre of graphene weighs 0.00077 grams).
what are the properties of gaphene
Very strong (up to 300 times stronger than steel) – each carbon atom is bonded to three other carbon atoms with strong covalent bonds that require a lot of force to break. Potential uses related to this property include replacement for Kevlar in bullet-proof vests.
Best conductor of electricity known – the delocalised electrons within the graphene layer can carry electrical energy. Potential uses related to this property include ultra-thin electronics such as foldable laptops.
