C3 Flashcards
three states of matter
solid, liquid and gas
solid
arrangement of particles with a fixed shape and volume, they cannot be compressed
liquid
arrangement of particles with a fixed volume but they can flow and change shape
gas
arrangement of particles with no fixed shape or volume, they can be compressed easily
compound
a substance made of two or more elements chemically bonded together
covalent bonding
bonding between non-metals only, in which electrons are shared
ionic bonding
bonding between metals and non-metals, in which electrons are transferred
positive ion
an atom that loses one or more electrons and gains a positive charge
negative ion
an atom that gains one or more electrons and gains a negative charge
electrostatic attraction
the strong force that holds ions together
giant lattice
the arrangement of ions in ionic bonding results in this structure
NaCl
sodium chloride
MgCl₂
magnesium chloride
Ca(OH)₂
calcium hydroxide
simple molecules
small molecules in which atoms are held together by covalent bonds
giant covalent structures
giant structures where atoms are held together by an array of covalent bonds
intermolecular forces
weak forces between covalently bonded molecules that must be broken when simple substances melt or boil
diamond
an allotrope of carbon in which all of the carbon atoms are bonded to 4 others resulting in an extremely strong structure
silicon dioxide
a giant covalent structure very similar to diamond but made from silicon and oxygen instead of carbon
graphite
an allotrope of carbon that has hexagonal sheets of carbon with weak attractive forces between the layers
fullerenes
an allotrope of carbon in which the carbon form cage like structures
delocalised electrons
electrons not linked with a particular ion that are free to move through a structure
graphene
a single sheet of carbon atoms (like one layer of graphite)
crystals
metal atoms build up layer upon layer to form these structures
alloys
a mixture of metals, typically much harder than metal atoms alone
How can you use the periodic table to help you remember charges on ions?
Look at the group number: Group 1 form +1 ions Group 2 = +2 Group 3 = +3 Group 4 = don't form ions Group 5 = -3 Group 6 = -2 Group 7 = -1 Group 0 don't form ions
What are the properties of simple molecular substances?
Gases, liquids (with low boiling points) or solids (with low melting points), usually non conductors.
Why do simple covalent compounds have low melting and boiling points?
They have weak forces of attraction between their molecules that take little energy to overcome.
What are the properties of giant covalent structures?
Solids with very high melting and boiling points.
Why do giant covalent structures have high melting points?
To melt you need to break STRONG covalent bonds between the atoms which requires a lot of energy.
Why do metals conduct electricity?
They have delocalised electrons which can flow when an electric field is applied across it.
Why are metals malleable?
Layers of cations in a metal lattice can slide over each other when a force is applied. The layers of ions are held together by the delocalised electrons.
Do ionic compounds conduct electricity?
Yes, but only when molten or in solution. The ions are then free to move. In solid ions have fixed positions and can not move.
