3.1.3 (b&s) covalent bonding Flashcards
what does covalent bonding happen between?
two non metal atoms sharing at least one pair of electrons
definition: covalent bonding
a covalent bond is a shared pair of electrons
when atoms combine by covalent bonds, what are formed?
molecules
what are non bonded pairs of outer electrons on a compound called?
lone pairs of electrons
what is the melting/ boiling point like in simple covalent molecules?
why?
low melting/boiling points
because they have weak intermolecular forces between the molecules which are easily broken
can simple covalent molecules conduct electricity?
why/why not?
no
because there are no delocalised electrons to carry a charge
what does the solubility of simple covalent molecules depend on?
the solubility in water and other solvents depends upon the degree of polarity in the molecule
what’s another term for giant covalent structures?
macromolecules
what are the two types of carbon macromolecules?
(giant covalent molecules)
graphite and diamond
what does the structure of graphite look like?
how are the carbon atoms arranged in graphite?
arranged into layers of flat hexagons with each carbon bonded to three other carbon atoms
what’s different about the 4th electron in graphite?
it’s delocalised between the layers
what are the hexagon layers in graphite bonded together by?
weak van der waals forces
what are 5 properties of graphite?
- it’s slippery
- it can conduct electricity
- it’s a low density material
- has a very high melting point
- it’s insoluble
how is graphite slippery?
the weak bonds between the layers are easily broken so the hexagon sheets can slide other one another making graphite slippery
how can graphite conduct electricity?
contains delocalised electrons which are free to move within each layer
how is graphite a low density material?
what can this be used to make?
the layers are relatively far apart compared to the length of covalent bonds making graphite low density
used to make strong lightweight sports equipment
what causes graphites very high melting point?
the strong covalent bonds in the hexagon layers
why is graphite insoluble?
as the covalent bonds in the hexagon layers are too difficult to break
what does the structure of diamond look like?
how many other carbons is each carbon atom bonded to?
4
how are the atoms arranged in diamond?
in a tetrahedral shape around a central atom forming a macromolecular crystal
what are 5 properties of diamond?
- high melting point
- hard
- good thermal conductor
- can’t conduct electricity
- insoluble
what causes diamond high melting point?
the strong covalent bonds between carbon atoms throughout the structure
