Structure & Properties Flashcards
Why do ionic solids have high melting points?
They have giant structures with strong electrostatic forces that hold the ions together and a lot of energy is needed to overcome the forces
What can the ions do when an ionic compound has been melted?
The ions are free to move
When can ionic compounds conduct electricity?
When molten or when dissolves in water and the water molecules split up the lattice
Why can ionic substances conduct electricity when molten or dissolved in a water?
They are free to move and carry a charge
Why can’t ionic compounds conduct electricity when solid?
The ions can only vibrate about fixed positions they cannot move around
What do the covalent bonds act between?
The covalent bonds act only between the atoms within the molecule
Why do simple molecules have relatively low melting points and boiling points?
The intermolecular forces between the locales are weak
What sort of boiling and melting points dos impel molecules have?
Low MP and BP
Why do cannot simple molecules carry an electrical charge?
They have no overall charge so cannot carry a charge
What state of matter do the simplest molecules with the weakest forces such as H2 and Cl2 exist in at room temperature?
Gas at room temperature
Which state of matter will larger molecules with stronger attractions exist as at room temperature?
Liquids or solids with low melting points
Why are substances with large molecules more likely to be liquids and solids at room temperature?
The intermolecular forces are stronger for larger molecules so they will require more energy to overcome so the point when these forces are over some (melting point) will be higher
Why do giant covalent structures/macromolecules have very high melting points?
It requires huge amounts of energy to break down the lattice and so these substances have very high melting points
How many atoms of carbon are covalently bonded to each other in diamond?
Every carbon atom is covalently bonded to four other carbon atoms
What properties does diamond have?
It is very hard and is transparent
Which compound has a similar structure to diamond?
Silicon dioxide (silica)
What is diamonds structure like?
Regular three dimensional giant structure
How many carbon atoms are covalently bonded in graphite?
The atoms are covalently bonded to 3 other carbon atoms
Why can graphite layers slide over each other?
There are no covalent bonds between the layers so they can slide over each other
Give 2 similarities and 2 differences between diamond and graphite
Similarities: forms of carbon
Giant covalent structures
Have covalent bonds
Differences: carbon atoms in diamond are bonded to four other carbon atoms only to 3 other atoms in graphite
Diamond is 3D, graphite is 2D
Diamond is hard, graphite is slippery and soft
Diamond is transparent, graphite opaque
Graphite is a good conductor of heat/electricity diamond is a poor conductor
Graphite has delocalised electrons, diamond does not
Graphite has intermolecular forces, diamond does not
In graphite what do the carbon atoms form?
A flat sheet of hexagons
Why ça granite conduct heat and electricity?
It has delocalised electrons wishing are free to more and carry a charge or transfer heat through out the graphite
Why can graphite layers slide over each other easily?
They have weak intermolecular forces between the layers
What are fullerenes?
Large molecules formed from hexagonal rings of carbon atoms
