1covalent bonding Flashcards
non metal atoms can share electrons with
other non metal atoms to obtain a full outer shell of electrons
when non metal atoms share pairs of electrons they form
covalent bonds
covalent bonds between atoms are
very strong
when two or more atoms are chemically bonded together they
form molecules
shared electrons are called
bonding electrons and occur in pairs
simple covalent molecules do not
conduct electricity as they do not contain free electrons
covalent bonding in terms of electrostatic attraction
There is a strong electrostatic attraction between the shared pair of electrons and the nuclei of the atoms involved, since the electrons are negatively charged and the nuclei are positively charged
simple molecular structures have
covalent bonds joining the atoms together, but intermolecular forces act between neighbouring molecules
covalent bonds- mp/bp
they have low melting and boiling points as there are only weak intermolecular forces acting between the molecules
as the molecules increase in size
the intermolecular forces also increase as there are more electrons available- this causes melting and boiling point to increase
as the relative molecular mass of a substance increases the melting/boing point will too- why
An increase in the relative molecular mass of a substance means that there are more electrons in the structure, so there are more intermolecular forces of attraction that need to be overcome when a substance changes state
So larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point
covalent bonds are poor conductors of electricity as
there are no free ions or electrons to carry the charge
most covalent compounds do not conduct electricity at all so are
insulators
giant covalent structures have
a huge number of non metal atoms bonded to other non metal atoms via strong covalent bonds- these structures are called giant lattices and have a fixed ratio of atoms in the overall structure
diamond and graphite are
allotropes of carbon
allotropes
different atomic or molecular arrangements of the same element in the same physical state
both diamond and graphite only
contain carbon atoms but due to the differences in bonding arrangements they are physically completely different
in diamond each carbon atom
bonds with four other carbons- forming tetrahedron
properties of diamond
It does not conduct electricity
It has a very high melting point
It is extremely hard and has a density of 3.51 g / cm3 – a little higher than that of aluminium
the four covalent bonds of diamond are
very strong and extend in a giant lattice so a very large amount of heat energy is needed to break the lattice
diamonds hardness makes it very useful for
purposes where extremely tough material its required
diamonds are used for
jewellery and coating blades in cutting tools
the cutting edges of discs used to cut bricks and concrete as well as heavy duty drill bits and tooling equipment are
tipped with Dimond
in graphite each carbon atom is
bonded to three others forming layers of hexagons, living one free electron per carbon atom
graphite can conduct electricity because
the free electrons migrate along the layers and are free to move and carry charge
covalent bonds within layers are very strong but
the layers are attracted to each other by weak intermolecular forces so the layers can slide over each other making graphite soft and slippery
properties of graphite
It conducts electricity and heat
It has a very high melting point
It is soft and slippery and less dense than diamond (2.25 g / cm3)
fullerenes are
a group of carbon allotropes which consist of molecules that form hollow tubes or spheres
fullerenes can be used to
trap other molecules by forming around the target molecule and capturing it, making them useful for targeted drug delivery systems
fullerenes have a
huge surface area and are useful for trapping catalyst molecules onto their surfaces making them easily accessible to reactants so catalysis can take place
