Presentation on theme: "Describe the arrangement of ions in a giant ionic structure. The ions are arranged in a lattice. There is attractive electrostatic forces between the ions."— Presentation transcript:
Describe the arrangement of ions in a giant ionic structure. The ions are arranged in a lattice. There is attractive electrostatic forces between the ions which are very strong e.g. sodium chloride ionic lattices.
Give two properties of giant ionic structures. They have very high melting and boiling points and can conduct electricity when melted or dissolved in water.
Can a solid ionic compound conduct electricity? No, because the ions are unable to move around when in a lattice structure. Ionic compounds can only conduct electricity when they have been supplied with enough energy to separate the ions.
What is meant by having an ionic compound in solution? This is when water molecules separate ions from the lattice. Ions are now able to move around freely within the solution and can therefore conduct electricity.
How are covalent bonds formed? This is when non-metal elements react to form compounds, so the atoms share electrons in their outer shell in order to gain a full out shell of electrons (like a noble gas). The bonds formed like this are called covalent bonds e.g. NH 3
Describe the bonding seen in a simple molecule. Covalent bonds are strong so the atoms within each molecule are held together tightly. Each molecule, though, is held together by weak intermolecular forces so overcoming these doesn’t take much energy.
Do simple molecules have high or low melting/boiling points? Low melting and boiling points. Most substances made up of simple molecules are therefore liquids or gases at room temperature.
Can simple molecules conduct electricity? No, because there is no overall charge in simple molecules and so their molecules cannot carry electrical charge.
Describe a giant covalent structure. These are huge networks of atoms held together by covalent bonds. Diamond, graphite and silicon dioxide all have giant covalent structures. They are very hard, have high melting and boiling points and are insoluble in water.
Why is diamond harder than other giant covalent structures? Because all of its carbon atoms each form four strong covalent bonds.
Why is graphite described as being slippery? Carbon atoms are only bonded to 3 other carbon atoms, they form hexagons which are in giant layers. There are NO covalent bonds between the layers so they can slide over each other.
Explain why graphite is able to conduct electricity? Carbon atoms have 4 electrons in their outer shell so in graphite one is left in each outer shell. These are free to move along the layers and are called delocalised electrons. This allows graphite to conduct electricity.
What a fullerenes? These are large carbon molecules containing cage-like structures. Scientists can now place other molecules inside these cages providing exciting uses e.g. delivery of drugs to specific sites in the body.
How are the atoms in pure metal arranged? They are held together in giant metallic structures for example in pure iron. The atoms are arranged in closely packed layers. The atoms are able to slide over each other due to its regular shape.
Why are alloys stronger than pure metal? Because the atoms in alloys are different sizes therefore stopping the atoms being able to slide over each other, therefore making it harder for the atoms to slide over each other.
What are the possible risks of using nanoparticles? Nanoparticles have a very large surface area and this although being good can be very dangerous. If they get into the air and then into our lungs they can damage them. They could enter the bloodstream this way and have detrimental effects.
Why are metals able to conduct electricity? The positive ions are held together by a sea of delocalised electrons. They are able to move throughout the giant lattice and allow electric current and heat to be transferred quickly throughout the metal.
Describe the bonding and properties in a thermosetting polymer? The atoms in the polymer chains are held together by very strong covalent bonds. The monomers between chains are covalently bonded and therefore when heated these polymers do not soften. The polymer will just char at very high temperatures, not soften.