Bonding, Structures and Properties Flashcards
what are ionic bonds between?
a metal and a non-metal
how do ionic bonds work?
the metal loses electrons from its outer shell to form positive ions and the non-metal gains the electrons in its outer shell to form negative ions
why do ionic compounds have high melting points/are solid at room temperature?
they consist of a regular pattern of oppositely charged ions with strong bonds between them
what is the effect of the charge on an ion on its melting point?
higher charge = higher melting point
why can ionic compounds conduct when molten/dissolved in water but not when solid?
in a solid the IONS are not free to move to the electrodes because they are held together by strong electrostatic forces of attraction.
when molten/dissolved the IONS are free to move and carry a charge
give examples of substances made up of simple molecules
- carbon dioxide
- water
explain why substances made up of simple covalent molecules have low melting/boiling points
little energy is needed to break the weak intermolecular forces
explain why substances made up of simple covalent molecules don’t conduct electricity
do not have any free electrons or any overall charge
give examples of giant covalent structures
- diamond
- silicon dioxide (sand)
- graphite
why does diamond have a high melting point?
it contains many strong covalent bonds extending throughout its whole giant 3-D tetrahedral lattice
why does diamond not conduct electricity?
all 4 valence electrons are used in bonding
why is graphite so soft?
it consists of layers, which can slide over each other. only 3 valence electrons are used in bonding, so there are many delocalised electrons to hold the structure together
why does graphite conduct electricity?
only 3 valence electrons are used in bonding, so there are many delocalised (free) electrons to carry a charge
how do the uses of diamond relate to its structure?
it is very hard due to the strong covalent bonds extending throughout its entire structure, so is used in cutting tools
how do the uses of graphite relate to its structure?
it is conductive, as it contains many delocalised electrons, so is used in electrodes
it is also very soft, due to its layered structure, so is used as a lubricant in engine oils
these layers also mean it can be used in pencils, as layers slide off onto the page
