Topic 2 - Bonding, Structure and Properties of Matter Flashcards
- Ions and Ionic Bonding
1) True or False? A positive ion is formed when an atom gains electrons.
2) Element X forms ions with a 2- charge. What is the group number of element X?
3) If an atom loses two electrons to form an ion, what charge will the ion have?
4) Describe how an ionic bond forms between a metal atom and a non-metal atom. Give your answer in terms of electron transfer.
5) A dot and cross diagram for sodium fluoride is shown on the right. Only the outer shells of electrons are shown in the diagram. Sodium is in Group 1 and fluorine is in Group 7. Identify two errors in the diagram.
6) Describe some limitations of using dot and cross diagrams to represent ionic bonding.
1) False - electrons are negatively charged, so atoms that gain electrons form negative ions.
2) Element X will have a group number of 6. Elements in Group 6 gain two electrons to get a stable electronic structure, forming 2- ions.
3) The ion will have a 2+ charge, as electrons are negatively charged.
4) The metal atom loses electrons to form a positively charge ion. The non-metal gains these electrons to form a negatively charged ion. These oppositely charged ions are strongly attracted to each other by electrostatic forces, forming an ionic bond.
5) The charge on the sodium ion should be 1+. Sodium is in Group 1 of the periodic table, so loses one electron to get a full outer shell, forming +1 ions. The fluoride ion should have eight electrons in its outer shell (only seven are shown in the diagram), as elements in Group 7 gain one electron to get a full outer shell of eight electrons.
6) Dot and cross diagrams don’t show the structure of the compound, the size of the ions or how the ions are arranged.
- Ionic Compounds
1) Do ionic compounds have high or low melting points?
2) Give one limitation of using ball and stick models to represent ionic compounds.
3) Explain why ionic compounds conduct electricity when molten, but not when solid.
4) The structure of compound A is shown in the diagram on the right. Describe the structure and bonding in A.
5) Compound A is made up of calcium ions and chloride ions. Calcium is in Group 2 and chlorine is in Group 7. What is the empirical formula of compound A.
1) Ionic compounds have high melting points. This is thanks to the strong electrostatic forces of attraction that exist between the ions.
2) The relative sizes of the ions may not be shown. There aren’t any gaps between the ions when the model suggests that there are.
3) In order for a substance to conduct electricity, it must contain charged particles that are free to move and carry the current. The ions in a solid ionic compound are held in place in the rigid lattice structure, so can’t move around. When an ionic compound melts, the ionic bonds break and the ions become free to move and can carry an electric current.
4) Compound A is an ionic compound, which has a giant ionic lattice structure. The ions form a closely packed regular lattice held together by ionic bonds. There are strong electrostatic forces of attraction between oppositely charged ions, in all directions.
5) Calcium is in Group 2, so forms 2+ ions in order to get a full outer shell. Chlorine is in Group 7, so forms 1- ions in order to get a full outer shell. The compound has to be neutral overall, so you have to have two chlorine ions to balance out the 2+ charge on the calcium ion. So the empirical formula of compound A is CaCl2.
- Covalent Bonding
1) How many electrons does each atom donate in a single covalent bond?
2) True or False? Non-metal atoms can form covalent bonds with each other.
3) The diagram on the right shows the structure of propane. What is the name given to this type of diagram?
4) What’s the molecular formula of propane? Use the diagram to help you.
5) Describe some limitations of using diagrams like the one above to represent a molecule.
6) Explain why carbon forms covalent bonds with four hydrogen atoms in CH4.
7) Why doesn’t a compound with the formular NH5 exist?
1) The atoms in a single covalent bond donate one electron each.
2) True - covalent bonds only form between non-metals.
3) It’s a displayed formula. It shows the covalent bonds as single lines between the atoms.
4) To find the molecular formula of a compound from a displayed formula, you just need to count how many atoms there are of each type. In the diagram, there are three C atoms and eight H atoms, so the molecular formula is C3H8.
5) It doesn’t show the 3D structure of the molecule. It also doesn’t give you any information about which atoms the electrons in the covalent bonds have come from.
6) A non-metal will generally try to form enough covalent bonds to fill its outer shell. Carbon has four electrons in its outer shell, so needs to form four single covalent bonds in order to get eight electrons in its outer shell.
7) Nitrogen already has five electrons in its outer shell, so only needs to form three single covalent bonds to get a full outer shell. If a nitrogen atom formed five covalent bonds to hydrogen atoms, it would have more than eight electrons in its outer shell.
- Simple Molecular Substances
1) What is the name of the molecule shown in the dot and cross diagram on the right?
2) Which of the following molecules contains a triple bond?
H2O NH3 N2 Cl2
3) Why don’t simple molecular substances conduct electricity?
4) Amelia makes the following statement: “The covalent bonds between nitrogen atoms are stronger than between hydrogen atoms. So, the boiling point of nitrogen will be higher than that of hydrogen.” Explain why Amelia isn’t necessarily correct.
5) The structure of hydrogen and methane are shown on the right. Which compound would have a higher boiling point? Explain your answer.
1) Hydrogen chloride - it’s got the molecular formula HCl.
2) N2 - it contains a N≡N triple bond.
3) Simple molecular substances aren’t charged, so there aren’t any free electrons or ions to carry an electric current.
4) The covalent bonds within a molecule aren’t broken when the substance boils - it’s the weak intermolecular forces that exist between the molecules that get broken. The strength of the intermolecular forces doesn’t depend on the strength of the covalent bonds within the molecule, so even though nitrogen has stronger covalent bonds than hydrogen, it might not have a higher boiling point.
5) The boiling point of a compound depends on the strength of the intermolecular forces that exist between the molecules. Larger molecules have stronger intermolecular forces, so methane will have a higher boiling point than hydrogen.
- Polymers and Giant Covalent Structures
1) How are the atoms in a polymer joined together?
2) Which element makes up diamond?
3) Look at the compound on the right. What physical state will it be at room temperature? Explain your answer.
4) Why do giant covalent structures have high melting points?
5) The melting points of two substances are shown in the table on the right. Explain the difference between the melting points of the two substances, in terms of their structure and bonding.
1) The atoms in a polymer are joined together by covalent bonds.
2) Diamond is made up of atoms of carbon.
3) It will be a solid. The compound is a polymer, and the intermolecular forces between polymer molecules are relatively strong. This means that they require a fair amount of energy to break, so almost all polymers are solids at room temperature.
4) In order to melt a giant covalent structure, you have to break the strong covalent bonds between the atoms. This requires a lot of energy, so giant covalent structures have high melting points.
5) In order to melt silica, you have to break the strong covalent bonds between the atoms. This requires a lot of energy, so silica has a high melting point. Poly (ethene) melts when relatively weak intermolecular forces are broken. Intermolecular forces are much weaker than covalent bonds, so poly(ethene) has a lower melting point than silica.
- Allotropes of Carbon
1) True or False? A buckminsterfullerene molecule is shaped like a ball.
2) Give one property of diamond.
3) In graphene, how many covalent bonds does each carbon atom form?
4) Name the type of carbon structure shown on the right?
5) Why can the structure on the right conduct thermal energy?
6) Describe the structure of graphite.
7) Give one application of graphene. Explain why the properties of graphene make it suitable for that application.
1) True - Buckminsterfullerene is a hollow sphere made of carbon atoms arranged in rings.
2) It is hard, it has a high melting point, it doesn’t conduct electricity.
3) Three - the carbon atoms in graphene are arranged in hexagons.
4) It’s a carbon nanotube.
5) In a carbon nanotube, each carbon only forms three bonds. So, each carbon atom has one delocalised electron that’s free to move around. These electrons can carry thermal energy around the structure (so carbon nanotubes are good conductors of heat).
6) Graphite is made up of carbon atoms arranged in hexagons. These hexagons join together to form sheets, which are held together weakly (by intermolecular forces).
7) There are a few answers here: e.g. graphene is very strong but also really light, so can be added to composites to improve their strength without adding much weight. Graphene can conduct electricity through the whole structure, so can be used in electronics.
- Metallic Bonding
1) Why do most metals have high melting points?
2) Why can most metals be easily bent and shaped?
3) Copper is a metal that is often used in electrical wiring. Explain how the structure of copper allows it to conduct electricity.
4) Bronze is an alloy made of copper and small amounts of tin. Describe how the structure of bronze makes it harder than pure copper.
5) Jamaal is shopping for a new garden bench. He goes to the garden centre to try out some benches. All the metal benches he sits on feel colder than any of the wooden benches that he tries, even though they are all the same temperature. Suggest why.
1) Metals are held together by strong metallic bonds, which require a lot of energy to break. It’s these bonds that are broken when metals melt, so most metals have high melting points.
2) The atoms in a metal are arranged in layers which can slide over each other, so metals can be bent or shaped without breaking the structure of the metal.
3) Copper has a giant metallic structure made up of metal ions and delocalised/free electrons. The delocalised/free electrons can move around the structure and carry a charge.
4) Bronze contains atoms of two different sizes (copper and tin). The tin atoms distort the layers of the copper atoms, which makes it harder for the layers to slide over each other, so bronze is harder than pure copper.
5) Metals are good conductors of heat (as they contain delocalised/free electrons). So when Jamaal sits on the metal benches, the heat is being moved away from his body much quicker than when he sits on the wooden benches. This makes the metal benches feel colder.
- States of Matter
1) Which of the following substances will expand to fill a container that it’s in?
A. Liquid water B. Nitrogen gas C. Solid Iron D. Cauliflower
2) How many gases are there in the chemical equation below?
MgCO3(s) + 2HCl(aq) –> MgCl2(aq) + H2O(l) + CO2(g)
3) What does it mean if a substance is ‘aqueous’?
4) A supersonic hedgehog is running around, collecting gold rings. As he runs, the air near his feet heats up. What effect will this have on the gas particles near his toes?
5) Describe the movement of particles in a liquid.
6) Give some limitations of using particle theory to describe the movement of particles.
1) Nitrogen gas - the particles in a gas are free to move, so gases don’t keep a definite shape or volume and will fill any container they’re in.
2) There’s only one substance in the equation that has the state symbol for a gas - CO2(g)
3) Aqueous means that the substance is dissolved in water.
4) Gas particles move faster at higher temperatures (because they have more energy), so the gas particles will speed up. The gas will also expand slightly, or its pressure will increase.
5) The particles in a liquid are randomly arranged and are free to move past each other, but tend to stick closely together. The particles are constantly moving with random motion.
6) In reality, the particles aren’t solid spheres (they’re atoms, ions or molecules). The particle model also doesn’t show the forces between the particles, so there’s no way of telling how strong the forces are.
- Changing State
1) What is the name for the process where a gas turns into a liquid?
2) What’s the main factor that determines the melting point of a substance?
3) Look at the table on the right. What physical state will iodine be in at 100ºC?
4) Which of the substances in the table on the right will be a gas at 110ºC?
5) A student is investigating the effect of temperature on the physical state of octane. He heats a sample of octane from 25ºC to 130ºC. Describe the changes that occur in the energy and arrangement of the particles over the course of the experiment.
1) Condensing - when a gas is cooled below its boiling point, it condenses.
2) The strength of the forces between the particles.
3) Iodine has a melting point of 114ºC, so it will be a solid at 100ºC. This is because the iodine particles won’t have enough energy to break free from their fixed positions and form a liquid.
4) Water is the only substance in the table that will be a gas at 110ºC. In order for a substance to form a gas, it has to be heated above its boiling point. Water has a boiling point of 100ºC, so water will be a gas at any temperatures above 100ºC. Both iodine and octane have boiling points higher than 100ºC, so won’t be gases at that temperatures.
5) Octane will be a liquid at 25ºC, as this temperature is above its melting point but below its boiling point. As the temperature increases, the particles of octane will gain more energy. This will make the particles move faster, which will weaken the forces that hold the liquid together. Once the temperature reaches the boiling point of octane (126ºC), the particles will have enough energy to break the forces between them. The liquid octane will boil/become a gas.
- Nanoparticles
1) True or False? Fine particles are larger than nanoparticles.
2) What’s the diameter of the smallest possible coarse particle?
3) The diameters of some different particles are shown below.
A. 150 nm B. 0.2 nm C. 50 nm D. 1000 nm
Which of the particles could be nanoparticles?
4) Silver catalysts work by providing a surface for molecules to react on. Why might a catalyst containing silver nanoparticles be more effective than one made from a sheet of silver foil?
1) True - fine particles are 100-2500 nm and nanoparticles are 1-100 nm.
2) 2500 nm / 2.5 x 10-6 m (Coarse particles have diameters of 2500-10 000 nm).
3) Nanoparticles have diameters between 1 nm and 100 nm - the only particle with a diameter that falls within this range is the 50 nm particle.
4) When it’s in the form of nanoparticles, silver has a much higher surface area to volume ratio that when it’s in bulk. So a catalyst made of silver nanoparticles would have a very high surface area for reactions to take place on.
- Uses of Nanoparticles
1) Give one property that a nanoparticle needs if it’s going to be used in a computer chip.
2) Suggest one use for a nanoparticle that has antibacterial properties.
3) Nanoparticles can be used in cosmetics to make them more effective. Suggest some possible risks of using nanoparticles in cosmetics.
4) A company has developed two different types of nanoparticle, A and B. Nanoparticle A has a ball-like structure and is soluble in water. Nanoparticle B is shaped like a thin rod and is slightly soluble in water. Which nanoparticle would be most suitable for delivering drugs to the body cells? Explain your answer.
1) The nanoparticle needs to be able to conduct electricity.
2) It could be added to fibres that are used to make bandages/surgical masks/wound dressings. It could be added to deodorants.
3) The long-term health impacts of nanoparticles aren’t known. The nanoparticles might damage the environment after they have been washed off the skin. The nanoparticles might be small enough to pass through the skin and remain in the body.
4) Nanoparticle A would be more suitable for drug delivery, as drugs could be carried within the ball structure and released once the nanoparticle reaches the target cell. Nanoparticle A is also more suitable in water than nanoparticle B, so would be absorbed more easily by the cells/travel more efficiently in the bloodstream.
