Topic 2 - Covalent Substances Flashcards
how are atoms within a molecule held together?
by very strong covalent bonds
what does weak intermolecular forces cause?
low melting and boiling points because molecules are easily separated
as relative molecular mass increases what happens to melting and boiling points?
they increase, as intermolecular forces are stronger, so more energy is needed to break the forces.
how are giant covalent structures different to giant ionic structures?
there are no charged ions in a covalent structure
how are atoms bonded in giant covalent structures?
strong covalent bonds
why do giant covalent structures have high melting/boiling points?
there are lots of covalent bonds which means it takes a lot of energy to break them
do giant covalent structures conduct electricity?
no - except graphite
are giant covalent structures soluble in water?
they are usually insoluble in water
what atoms is diamond made up of?
a network of carbon atoms that each form 4 covalent bonds
why does diamond have a high melting point?
the strong covalent bonds take a lot of energy to break
why are diamonds hard?
the strong covalent bonds hold the atoms in a rigid lattice structure
do diamonds conduct electricity?
no, because it has no free electrons or ions
what atoms is graphite made up of?
layers of carbon atoms where each carbon atom forms three covalent bonds. the layers are held together weakly by intermolecular forces, so can slide over each other.
does graphite have a high melting point?
yes, the covalent bonds in the layers need a lot of energy to break
can graphite conduct electricity?
yes. only 3/4 of carbon’s 4 outer electrons are used in bonds, so each atom has one delocalised electron that can move.
