C3 Flashcards
non-metallic elements form
simple molecules with covalent bonds between atoms
covalent substances are formed when?
when atoms of non-metals combine.
describe the formation of single covalent bonds
they are the sharing of pairs of electrons leading to the noble gases configuration (see dot and cross diagrams - the ones that overlap on pg 49)
Describe the differences in volatility between ionic and covalent compounds.
Covalent compounds have low melting and boiling points.
Ionic bounds have high boiling and melting points.
Covalent compounds are more volatile.
(volatile = evaporates easily)
Describe the differences in solubility between ionic and covalent compounds.
ionic compounds are usually soluble in water
covalent compounds are less soluble.
Describe the differences in electrical conductivity between ionic and covalent compounds.
Ionic compounds can conduct electricity when melted or dissovled, and the lattice breaks up and ions are free to move.
Covalent compounds are not charged, thus they do not conduct electricity.
know how to draw the diagrams for more complex covalent molecules
pg 51
what kind of intermolecular forces do ions and simple covalent compounds have (why are ions’ melting and boiling points higher?)
ions have strong intermolecular forces (so high melting and boiling points)
simple covalent has weak intermolecular forces (so low melting and boiling points)
- they have different attractive forces. ions’ are harder to break
what are allotropes
they are different forms of the same element
what are allotropes
they are different forms of the same element
there are many different forms of _____
carbon. including diamond and graphite.
describe the giant covalent structures of graphite and diamond.
diamond: each carbon atom is joined to four other carbon atoms by strong covalent bonds. the carbon atoms form a regular network structure. there are no free electrons
graphite: each carbon atom forms three covalent bonds with other carbon atoms. the carbon atoms form layers of hexagonal rings. there are no covalent bonds between the layers. there is one non-bonded - or delocalised - electron from each atom
how do the structures of diamond and graphite relate to their uses?
all the covalent bonding in diamond is very strong which makes an extremely hard substance. it’s why diamonds are used in cutting.
graphite also has strong covalent bonds, but they have weak forces of attraction (weak IMFs). so, the layers slide over each other which makes It a good lubricant. it can also conduct electricity.
describe the macromolecular structure of silicon oxide
every silicon atom has four covalent bonds, it is similar to diamond which is why silicon oxide is hard and has a high melting point.
