Topic 1 - Atomic Structure and the Periodic Table Flashcards
- Atoms and Elements
1) What is the charge of a neutron? What is its relative mass?
2) Explain what is meant by the term “isotopes”.
3) True or False? Most of the mass of an atom is located in the nucleus.
4) Why do atoms have no charge?
5) How many neutrons does an atom of the element on the right have? 88 Sr
38
6) Why is the relative atomic mass of chlorine not a whole number?
7) Freda is building a model of an atom. She wants to use her prize turnip as the nucleus. The turnip has a radius of 20cm. What will the radius of the whole atom be?
1) A neutron’s relative charge is 0. Remember neutrons are neutral. The relative mass of a neutron is 1.
2) Isotopes are different forms of the same element, which have the same number of protons but different number of neutrons.
3) True - Electrons have virtually no mass
4) Atoms have the same number of protons as electrons. Because the charge on protons (+1) and electrons (-1) are opposite and equally-sized, they cancel each other out.
5) Number of neutrons = mass number - atomic number = 88-38 = 50
6) Chlorine has more than one isotope. Relative atomic mass is an average that takes into account the different masses and abundances of all the isotopes that make up an element.
7) The radius of an atom is around 10 000 times the size of the radius of the nucleus. So 20cm x 10 000 = 200,000cm (or 2km - hopefully Freda has a large garden).
- Compounds and Chemical Equations
1) True or False? The properties of a compound are always similar to those of the elements that make it up.
2) How many carbon atoms are there in a molecule of calcium carbonate, CaCO3?
3) Are reactants found on the left-hand side or right-hand side of a chemical equation?
4) What is a compound?
5) Two atoms of aluminium, Al, will react with three atoms of oxygen, O, to form one molecule of aluminium oxide. No other products are formed. What is the formula of aluminium oxide?
6) What type of process is needed to separate a compound into its elements?
7) What number needs to go in front of CO2 to balance the following equation? C6H8O7 + 3NaHCO3 –> CO2 + 3H2O + Na3C6H5O7
1) False. Compounds often have totally different properties to the original elements.
2) There is one carbon atom in a molecule of CaCO3 (plus one calcium atom and three oxygen atoms)
3) The left-hand side
4) A compound is a substance formed from two or more different elements in fixed proportions, held together by chemical bonds.
5) No other products are formed, so both atoms of aluminium and all three atoms of oxygen must end up in the aluminium oxide. So the formula is Al2O3.
6) You need a chemical reaction to separate compounds into elements.
7) There are 9 carbon atoms on the left-hand side of the equation, so there needs to be 3 molecules of CO2 to make sure there are also 9 carbon atoms on the right-hand side.
- Mixtures and Chromatography
1) Why should you pit a lid on the container during a paper chromatography experiment?
2) True or False? When substances are combined in a mixture, their chemical properties change.
3) What is a solvent front?
4) What is a mixture?
5) Explain why techniques to separate mixtures are described as physical processes.
6) Stephen is doing a paper chromatography experiment. He uses a pen to draw a line near the bottom of the filter paper. Why is this wrong?
7) Explain how paper chromatography could be used to separate a mixture containing three different dyes.
1) A lid helps stop the solvent from evaporating.
2) False. The chemical properties of the substances in a mixture are unchanged.
3) The point that the solvent in paper chromatography reaches as it moves up the paper.
4) A mixture consists of two or more elements or compounds that are combined, but not chemically bonded together.
5) The separation of a mixture is a physical process because it does not involve any chemical reactions, and no new substances are made.
6) The line should be drawn in pencil - pen contains ink that will dissolve in the solvent.
7) Put a dot on the dye mixture on the pencil line and place the filter paper in solvent. Each different dye in the mixture will move up the paper at a different rate, separating out the dyes. You’ll end up with 3 separate spots on your chromatogram (provided all three dyes dissolve in the solvent).
- Filtration and Crystallisation
1) When can filtration be used to separate a mixture?
2) When is crystallisation used to separate a mixture?
3) Explain how filtration works.
4) Why might crystallisation be used instead of evaporation?
5) What equipment would you need to carry out a crystallisation?
6) What equipment would you need to carry out a crystallisation?
7) Explain how filtration and crystallisation can be used to separate a mixture of sand and salt.
1) Filtration can be used when you have a mixture of an insoluble solid and a liquid.
2) Crystallisation is used to separate a soluble solid from a solution.
3) Filtration works by passing the mixture through a filter. The liquid passes straight through, but the insoluble solid particles are caught by the filter.
4) Crystallisation is used if the salt will decompose when heated, or if you want to make big crystals of the salt.
5) To carry out a crystallisation, you’d need an evaporating dish and a heat source. And once you’ve got your crystals, they’ll need to be filtered out of the solution, so you’d need a beaker of flask, funnel and some filter paper.
6) Salt is soluble in water, whereas sand is not. If water is added, the salt will dissolve. The mixture can then be filtered to remove the insoluble sand. They crystallisation can be used to separate the salt from the water.
- Distillation
1) In fractional distillation, where is the hottest point of the fractionating column?
2) What sort of mixture can fractional distillation be used to separate?
3) Explain why simple distillation can’t be used to separate substances with similar boiling points.
4) What is the name of the apparatus labelled B in the diagram on the right? What is it used for in this setup?
5) Cyclohexane, cyclopentane and acetone have boiling points of 81ºC, 49ºC and 56ºC respectively. Describe how you could use fractional distillation to separate a mixture of these compounds.
1) The bottom of the fractionating column is the hottest.
2) Mixtures of liquids, including those with similar boiling points.
3) If the boiling points of the compounds are too close together, they will all evaporate and mix together again.
4) It’s a condenser. It cools the vapour and turns it back into a liquid, so it can be collected.
5) Prepare a setup with a flask placed below a fractionating column, which is connected to a condenser and has a thermometer at the top. Pour the mixture into the flask and heat it to a temperature between 49ºC and 56ºC, so the cyclopentane evaporates but the other two compounds remain in the flask as liquids. The cyclopentane travels up the fractionating column and into the condenser, where it turns back into a liquid which can be collected. The increase the temperature to between 56ºC and 81ºC, so the acetone evaporates. It can be collected in a different container. The cyclohexane is left in the flask.
- The History of the Atom
1) True or False? Electrons were discovered before protons and neutrons.
2) What was the plum pudding model of the atom?
3) Which model replaced the plum pudding model?
4) Describe how alpha particles were used to disprove the plum pudding model.
5) How did James Chadwick contribute towards our understanding of the atom?
6) What did Niels Bohr suggest about the arrangement and movement of electrons in an atom?
1) True. The discovery of the electron led to the plum pudding model. Protons and neutrons weren’t discovered until much later, after the nuclear model had been proposed.
2) The plum pudding model described atoms as balls of positive charge with electrons stuck in them.
3) The nuclear model replaced the plum pudding model.
4) Alpha particles were fired at a thin sheet of gold. Most of the particles went straight through the sheet, but some were deflected more than expected and a small number were even deflected backwards. This meant that the positive charge couldn’t be spread out evenly within the atoms, as described by the plum pudding model.
5) James Chadwick provided evidence for the existence of neutrons within the nuclei of atoms.
6) Bohr suggested that electrons orbit the nucleus in shells that are a fixed distance from the nucleus. His theory stated that the electrons can only be found in these shells (and not in between them).
- Electronic Structure
1) True or False? In an atom, the highest energy levels are filled by electrons first.
2) How many electrons are required to fill the first electron shell in an atom?
3) What is the maximum number of electrons that can go in the second electron shell in an atom?
4) What is the electronic structure of the atom on the right?
5) The atomic number of oxygen is 8. What is the electronic structure of oxygen?
6) The atomic number of phosphorus is 15. What is the electronic structure of phosphorus?
7) Magnesium has 12 electrons. Does magnesium have a partially filled outer shell? Explain your answer.
1) False. The lowest energy levels are always filled first.
2) 2
3) 8
4) The atom has 2 electrons in its first shell, then 5 electrons in its second shell. So the electronic structure is 2, 5.
5) Oxygen’s atomic number is8, so it has 8 protons and 8 electrons. 2 electrons will fill the first shell and the remaining 6 will go in the second shell. The electronic structure is 2, 6.
6) Phosphorus’ atomic number is 15, so it has 15 protons and 15 electrons. The first 2 electrons will fill the first shell, the next 8 will fill the second shell and the remaining 5 will go in the third shell. So the electronic structure is 2, 8, 5.
7) Magnesium has 12 electrons. The first 2 electrons will fill the first shell and the next 8 will fill the second shell. This leaves 2 electrons in the third shell, so it is partially filled.
- The Periodic Table
1) How were elements arranged in the first periodic tables?
2) True or False? Mendeleev considered the properties of isotopes when constructing his periodic table.
3) What is the name for the vertical columns in the periodic table?
4) Explain why the way the elements are ordered in the modern periodic table is more useful than the way they were ordered in the first periodic tables.
5) Why do elements in the same column of the periodic table have similar properties?
6) Calcium is in the second column and fourth row (period) of the periodic table. How many occupied electron shells does calcium have? How many electrons are in calcium’s outer shell?
1) Relative atomic mass / atomic weight
2) False. The existence of isotopes wasn’t discovered until later (but they proved that Mendeleev was right to consider properties of elements as well as relative atomic mass when ordering elements in his periodic table).
3) The columns in the periodic table are known as groups.
4) In the modern periodic table, the elements are ordered by atomic number instead of relative atomic mass. This takes into account the existence of isotopes, and means elements end up in the same group as other elements with similar properties.
5) Elements in the same group have the same number of electrons in their outer shell.
6) Calcium is in the fourth row (period) of the periodic table, so it has four shells containing electrons. Calcium is in the second column (group), so it has two electrons in its outer shell.
- Metals and Non-Metals
1) What is a metal?
2) Where in the periodic table are metals found?
3) Describe the general properties of metals.
4) Explain why most metals have similar physical properties.
5) Bilal and Lucy are arguing about non-metals. Bilal thinks non-metals readily form positive ions. Lucy thinks it’s difficult for non-metals to form positive ions, and that Bilal needs some revision flashcards or something. Who is right? Explain your answer.
6) Why is it easy for elements towards the bottom of the periodic table to lose electrons?
1) Metals are elements which can form positive ions.
2) Metals are found towards the left and bottom of the periodic table.
3) Metals are strong, malleable, good conductors of heat and electricity and have high melting and boiling points.
4) All metals have metallic bonding, which causes them to have similar physical properties.
5) Lucy is right. Non-metals are found towards the right and top of the periodic table. They have lots of electrons that would have to be removed to give them a full outer shell, and therefore a stable positive ion. The elements towards the top of the periodic table also have their outer electrons close to the nucleus. This means they are strongly attracted, so it requires a lot of energy to remove them.
6) Elements at the bottom of the periodic table have more shells of electrons than elements at the top, so their outer electrons are further from the nucleus. Because of this, the outer electrons feel a weaker attraction and are more easily lost.
- Transition Metals
1) Where are transition metals found in the periodic table?
2) Name your three favourite transition metals.
3) True or False? Transition metals are less reactive than Group 1 metals.
4) How do the melting points and densities of transition metals compare to the melting points and densities of Group 1 metals?
5) Which property of transition metals is demonstrated by the use of iron in the Haber process?
6) What are two other properties of transition metals that aren’t exhibited by Group 1 metals?
1) Transition metals are found in the centre of the periodic table.
2) Copper, Iron and Nickel
3) True. Group 1 metals will react much more vigorously with water, oxygen or Group 7 elements.
4) Transition metals are much more dense than Group 1 metals. They also have much higher melting points.
5) Transition metals make good catalysts. An iron catalyst is used in the Haber process to speed up the reaction.
6) Transition metals can form more than one ion.
They also form colourful compounds.
- Group 1 Elements
1) How are the elements in Group 1 of the periodic table more commonly known?
A. Acid metals B. Alloy metals C. Alkali metals D. Awful metals
2) True or False? Group 1 metals are soft.
3) Why do the elements in Group 1 share similar properties?
4) The melting points, in ºC, of some Group 1 metals are: lithium (180.5), sodium (97.8), rubidium (39.5). Predict the melting point of potassium.
5) What is the trend in the reactivity down Group 1. Explain your answer.
6) What might you observe in the reaction between potassium and water?
7) What are the products when sodium reacts with oxygen?
1) Alkali metals
2) True. Alkali metals are soft with low density.
3) The elements in Group 1 all have one electron in their outer shell/all form 1+ ions, giving them similar properties.
4) Any value between 39.5ºC and 97.8ºC is a good answer (the real answer is 63.5ºC). The melting points of the alkali metals decrease down the group.
5) The reactivity of the Group 1 metals increase down the group. This is because the outer electron is further from the nucleus, so is less attracted and is more easily lost.
6) Potassium reacts vigorously with water. Hydrogen gas is produced during the reaction, so there would be fizzing/bubbling. The energy given out is high enough that the potassium melts and the hydrogen can be ignited, so a flame would also be seen.
7) Sodium reacts with oxygen to form sodium oxide (Na2O) and sodium peroxide (Na2O2).
- Group 7 Elements
1) What sort of compounds do halogens form with other non-metals?
2) What is the charge on a halide ion?
3) Chlorine is a gas at 25ºC. Predict the state of fluorine at 25ºC. Explain your answer.
4) What is the molecular formula of a fluorine molecule?
5) Describe the trend in reactivity down Group 7. Explain your answer.
6) Will chlorine displace bromine from a solution of potassium bromide? Explain your answer.
1) Halogens react with other non-metals to form simple molecular compounds. These compounds contain covalent bonds (shared pair of electrons).
2) Halogen atoms need to gain one electron to complete their outer shell. So they form 1- ions.
3) As you go down Group 7, the boiling points (and melting points) of the halogens increase. Fluorine is above chlorine, so it has a lower boiling point. So fluorine must also be a gas.
4) All halogens exist as molecules made from a pair of atoms. So fluorine exists as F2.
5) The reactivity of the halogens decreases down Group 7, because the outer shell becomes further from the nucleus. So there’s less attraction and it’s harder to gain an electron.
6) Chlorine will displace bromine from a solution of potassium bromide, because chlorine is more reactive than bromine. More reactive halogens can displace other halogens from solutions of their salts.
- Group 0 Elements
1) How many electrons does helium have in its outer shell?
2) How many electrons do the other noble gases, apart from helium, have in their outer shells?
3) Does krypton have a lower or higher boiling point than argon? Explain your reasoning.
4) Explain why the noble gases elements are inert (don’t react).
5) The Group 0 elements exist as monatomic gases. What does this mean?
6) Would xenon make a good fuel? Explain your answer.
1) Helium has two electrons in its outer shell. (It’s still full though, because the first shell only needs two electrons to be filled).
2) The rest of the noble gases have eight electrons in their outer shells.
3) Krypton has a higher boiling point than argon. Krypton is below argon in Group 0, and the boiling points of the noble gases increase as you go down the group. This is because the relative atomic mass (and number of electrons) increases, so there are greater intermolecular forces between the atoms which need to be overcome.
4) The noble gases are inert because they have full outer shells, so don’t need to lose or gain any electrons to become stable.
5) The noble gases exist as single atoms, not bonded to each other.
6) The noble gases are so inert that they are non-flammable. So xenon would make a very poor fuel indeed.
