chemistry chapter 5 structural properties Flashcards
(26 cards)
What are the structural properties of ionic compounds?
high melting/boiling points, solids at room temperature, hard and brittle, soluble in water but insoluble in organic compounds, conducts electricity in molten/aqueous state but not in solid state.
Describe the structure of ionic compounds.
giant ionic crystal lattice structure with large number of alternating (+) and (-) ions held together by electrostatic forces of attraction.
Why do ionic compounds have high melting and boiling points?
mutual electrostatic forces of attraction between the oppositely charged ions are strong, and large amounts of energy are needed to overcome the forces.
why are ionic structures hard?
the strong forces of attraction result in the structure being resistant to deforming.
Why are ionic structures brittle?
when enough force is applied, repulsive forces between the ions of the same charge become larger than the attractive forces. as such, the lattice structure shatters.
What are the structural properties of simple covalent molecules?
low melting/boiling points, gases/liquids at room temperature, insoluble in water but soluble in organic solvents, cannot conduct electricity.
Why are simple covalent molecules gases or liquids at room temperature?
although they have strong covalent bonds, the intermolecular forces of attraction are weak and can be easily overcome with small amounts of energy.
Why are simple covalent molecules unable to conduct electricity?
they do not have any mobile charge carriers to conduct electricity. only some can dissociate in water and can conduct electricity.
what are the structural properties of giant covalent molecules?
very high melting/boiling points, insoluble in water and organic solvents. structures like diamond are hard and cannot conduct electricity while structures like graphite are soft and slippery, able to conduct electricity along layers.
O2 and O3 are simple covalent molecules. Which one has a higher melting point and why?
Ozone has a higher melting point. It has a larger molecular size and hence the intermolecular forces of attraction are stronger, requiring more thermal energy to overcome.
Why are giant covalent structures almost always in solid state while simple covalent molecules are liquids or gases in room temperature?
Both have strong covalent bonds. However, simple covalent molecules have weak intermolecular forces of attraction while giant molecular structures consist of many atoms all connected by strong covalent bonds.
Describe the structure of diamond.
each carbon atom forms covalent bonds with four other carbon atoms, forming a tetrahedral arrangement.
Describe the structure of graphite.
Each carbon atom forms covalent bonds with three other carbon atoms, forming layers of carbon atoms. these layers are held together by weak intermolecular forces of attraction.
give examples of allotropes of carbon.
diamond, graphite, silicon dioxide.
describe how the different structures of diamond and graphite result in different uses for them.
diamond is hard and hence is used to coat drill bits. graphite is smooth and slippery and hence makes a good lubricant or pencil lead as it easily marks paper when the layer of graphite shears off.
give examples of simple covalent molecules that dissociate in water.
hydrogen chloride and ammonia.
why can graphite conduct electricity?
each carbon atom is bonded to only three other carbon atoms, leaving one unbounded electron per carbon atom, leaving it free and mobile to conduct electricity.
what are the structural properties of polymers (macromolecules) ?
varying melting/boiling points but mostly solids at room temperature, insoluble in water but soluble in organic solvents, cannot conduct electricity.
describe the structure of metals.
(+) charged metal ions evenly distributed throughout the solid, with a sea of delocalised electrons.
are alloys with fixed distribution of atoms?
no, they are mixtures and only an approximated percentage of each element by mass is known.
what leads to difference in properties between alloys and metals?
metals have regular arrangements off atoms but alloys have randomly distributed atoms of another element, disrupting the orderly arrangement and results in an irregular lattice arrangement.
what are the structural properties of metals?
high melting/boiling points, malleable and ductile, good conductors of electricity.
what are the structural properties of alloys?
range of melting/boiling points, good conductors of electricity, harder and stronger than regular metals.
why are metals malleable and ductile?
layers of atoms can slide over one another easily. sea of delocalised electrons will hold metal ions together unless much stronger force is applied.
