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Topic 1 - Atomic Structure and the
Periodic Table Questions & Answers
15 The elements in Group 1 of the periodic table are metals. (a) The elements in Group 1 are called the alkali metals. Why are they called the alkali metals? [2 marks] (b) Explain the increase in reactivity of elements further down the group. [4 marks] - ANSWERS(a) because they form hydroxides that give alkaline solutions (in water) (b) the atoms have more electron shells (as move down the group) so the electron in the outer shell is further away from the nucleus which reduces the attraction to the nucleus so the electron is lost more easily from the atom 20(b) Sulfur dioxide dissolves in water. What colour is universal indicator in a solution of sulfur dioxide? Give a reason for your answer [2 marks] - ANSWERS(b) red / orange / yellow because sulfur dioxide (when in solution) is an acid 20(c) Sulfur dioxide is a gas at room temperature. The bonding in sulfur dioxide is covalent. Explain, in terms of its structure and bonding, why sulfur dioxide has a low boiling point. [3 marks] - ANSWERS(c) (there are) weak forces (of attraction) between the molecules (these) take little energy to overcome as the concentration of thiosulfate solution doubles, the rate of reaction doubles. explain in terms of particles. 3 marks - ANSWERSthe number of particles per unit volume increases. therefore the frequency of successful collisions increases. so the number of particles per unit volume doubles and the frequency of collisions doubles. Q1.The figure below shows magnesium burning in air.
(b) Name the product from the reaction of magnesium in the figure. - ANSWERS(b) Magnesium oxide (c) The magnesium needed heating before it would react. What conclusion can you draw from this? - ANSWERS(c) The reaction has a high activation energy 1 (e) Why are nanoparticles effective in very small quantities? - ANSWERS(e) They have a high surface area to volume ratio 1 (f) Give one advantage of using nanoparticles in sun creams. - ANSWERS(f) any one from:
- Better coverage
- More protection from the Sun's ultraviolet rays 1 g) Give one disadvantage of using nanoparticles in sun creams. - ANSWERS(g) any one from:
- Potential cell damage to the body
- Harmful effects on the environment 4 (c) Suggest two reasons why 9 carat gold is often used instead of pure gold to make jewellery. - ANSWERS(c) any two from:
- cost (9 carat is cheaper)
- pure gold is soft or 24 carat gold is soft or 9 carat gold is harder
- can change the colour Q5.This question is about hydrocarbons. (a) The names and formulae of three hydrocarbons in the same homologous series are: Ethane C2H Propane C3H Butane C4H The next member in the series is pentane. What is the formula of pentane? - ANSWERS(a) C5H 5 d) Octane (C8H18) is a hydrocarbon found in petrol. Explain why octane is a hydrocarbon. - ANSWERS(d) contains hydrogen and carbon (hydrogen and carbon) only 1 (b) Why is aluminium positioned in Group 3 of the periodic table? - ANSWERS(b) has three electrons in outer energy level / shell 1 (c) In the periodic table, the transition elements and Group 1 elements are metals. Some of the properties of two transition elements and two Group 1 elements are shown in the table below.
(a) Suggest one improvement to step 2 to make sure all the salt is dissolved in the water. (b) The salty water in step 4 still contained very small grains of sand. Suggest one improvement to step 4 to remove all the sand. (c) Suggest one safety precaution the students should take in step 5. - ANSWERS(a) any one from:
- heat
- stir 1 (b) filter (c) any one from:
- wear safety spectacles
- wear an apron 2d describe how simple distillation works - ANSWERS(d) evaporation at A condensation at B 3 a) Why does iodine have a higher boiling point than chlorine? - ANSWERS(a) The forces between iodine molecules are stronger 5b ii Describe a method for making pure crystals of magnesium chloride from magnesium and dilute hydrochloric acid. In your method you should name the apparatus you will use. You do not need to mention safety. [6] - ANSWERSexamples of the points made in the response:
- hydrochloric acid in beaker (or similar)
- add small pieces of magnesium ribbon
- until magnesium is in excess or until no more effervescence occurs
- filter using filter paper and funnel
- filter excess magnesium
- pour solution into evaporating basin / dish
- heat using Bunsen burner
- leave to crystallise / leave for water to evaporate / boil off water
- decant solution
- pat dry (using filter paper). 6 (b) Explain why an atom has no overall charge. Use the relative electrical charges of sub-atomic particles in your explanation - ANSWERS(b) (because the relative electrical charges are) −(1) for an electron and +(1) for a proton and the number of electrons is equal to the number of protons
6 (c) Explain why fluorine and chlorine are in the same group of the periodic table. Give the electronic structures of fluorine and chlorine in your explanation. - ANSWERS(c) (the electronic structure of) fluorine is 2,7 and chlorine is 2,8, (so fluorine and chlorine are in the same group) because they have the same number of or 7 electrons in their highest energy level or outer shell Q1.This question is about the reaction of ethene and bromine. The equation for the reaction is: C2H4 + Br2 → C2H4Br (b) When ethene reacts with bromine, energy is required to break covalent bonds in the molecules. Explain how a covalent bond holds two atoms together. [2] - ANSWERS(b) electrostatic force of attraction between shared pair of negatively charged electrons and both positively charged nuclei (d) Figure 3 shows the reaction between ethene and chlorine and is similar to the reaction between ethene and bromine. The more energy levels (shells) of electrons an atom has, the weaker the covalent bonds that it forms." Use the above statement to predict and explain how the overall energy change for the reaction of ethene with chlorine will differ from the overall energy change for the reaction of ethene with bromine. [6] - ANSWERSSize and strength
- chlorine atoms have fewer electron energy levels / shells
- chlorine atoms form stronger bonds
- Cl-Cl bond stronger then Br-Br
- C-Cl bond stronger that C-Br Energies required
- more energy required to break bonds with chlorine
- more energy given out when making bonds with chlorine
- overall energy change depends on sizes of energy changes
Q5.Glass is made from silicon dioxide (a) Silicon dioxide has a very high melting point. Other substances are added to silicon dioxide to make glass. Glass melts at a lower temperature than silicon dioxide. Suggest why. - ANSWERS(a) weaker bonds or fewer bonds or disruption to lattice 5 (b) Sodium oxide is one of the substances added to silicon dioxide to make glass. (i) Sodium oxide contains Na+ ions and O2- ions. Give the formula of sodium oxide. - ANSWERS(i) Na2O 5 (c) Glass can be coloured using tiny particles of gold. Gold is a metal. Describe the structure of a metal. [3] - ANSWERS(c) lattice / regular pattern / layers / giant structure / close-packed arrangement (of) positive ions or (of) atoms (with) delocalised / free electrons 4d (ii) Why does iodine not react with sodium bromide solution? - ANSWERS(ii) iodine is less reactive (than bromine) 5 (b) A chemistry teacher demonstrated the reaction between sodium and water to a class of students. One of the students wrote the following notes: The reaction between sodium and water A piece of sodium was cut easily into smaller pieces with a knife. The sodium was added to some water in a trough. The sodium:
- floated
- melted quickly to give a silvery ball
- moved on the surface of the water
- fizzed Use the information in the box to help you answer these questions. What evidence is there that: (i) sodium has a low melting point (ii) sodium is soft (iii) a gas was produced? - ANSWERS(b) (i) quickly melted (ii) easily cut
(iii) effervescence / fizzing / bubbling 6 (f) Nanoparticles of sodium chloride (salt) are used to flavour crisps. What are nanoparticles? - ANSWERS(f) very small (particles) ignore tiny / small / smaller / microscopic etc. 1-100nm in size or (particle with a) few hundred atoms 7 (d) In 1869 Mendeleev produced his periodic table. Why did Mendeleev leave gaps in his periodic table? - ANSWERS(d) for undiscovered elements 8 (b) Suggest one reason why hydrogen should not have been put in column 1. - ANSWERS(b) it is a non-metal 8 (c) In 1895, the first of a new family of elements was discovered. One of the new elements was called helium. Where has this new family of elements been placed in the modern periodic table? - ANSWERS(c) to the right of column 7 / Group 7 8 (d) Complete the sentence. In the periodic table on your Data Sheet, the elements are arranged in order of their atomic ..................................... - ANSWERS(d) (atomic) number 4 (b) In 1869 Dmitri Mendeleev produced his version of the periodic table. Why did Mendeleev leave gaps for undiscovered elements in his periodic table? - ANSWERS(b) so that elements with similar properties could be placed together 4 (d) Lithium, sodium and potassium are all in Group 1 of the modern periodic table. Explain why. - ANSWERS(d) all have one electron in the outer shell (highest energy level) (so they) have similar properties or react in the same way Q5.This question is about the halogens (Group 7). (a) How do the boiling points of the halogens change down the group from fluorine to iodine? - ANSWERS(a) increase 5b iii) Why does chlorine displace bromine from sodium bromide? - ANSWERS(iii) chlorine is more reactive than bromine 5b iv) Use the Chemistry Data Sheet to help you to answer this question. Suggest which halogen could react with sodium chloride solution to produce chlorine - ANSWERS(iv) fluorine
- (react with water) to form an alkaline / hydroxide solution
- form ions with a 1+ charge 9 (b) Newlands' periodic table was not accepted by most chemists in 1866. Suggest reasons why. [3] - ANSWERS• some boxes contain two elements
- groups / columns contain elements with different properties
- Newlands not a well-known / respected scientist
- new idea (not readily accepted by other scientists) 9 (c) State and explain one way in which Mendeleev improved Newlands' periodic table.
- ANSWERS• left gaps (for undiscovered elements)
- so that elements were in their correct group
- did not always follow order of relative atomic weights / masses
- so that elements were in their correct group 1 (a) Hydrogen was placed at the top of Group 1 in the early version of the periodic table. The modern periodic table does not show hydrogen in Group 1. (i) State one similarity between hydrogen and the elements in Group 1. (ii) State one difference between hydrogen and the elements in Group 1. - ANSWERS(a) (i) any one from:
- one electron in the outer shell / energy level
- form ions with a 1+ charge 1 (ii) any one from:
- hydrogen is a non-metal
- (at RTP) hydrogen is a gas
- hydrogen does not react with water
- hydrogen has only one electron shell / energy level
- hydrogen can gain an electron or hydrogen can form a negative / hydride / H- ion
- hydrogen forms covalent bonds or shares electrons 1b (iii) Explain, in terms of electronic structure, why fluorine is the most reactive element in Group 7. [3] - ANSWERS(iii) fluorine is the smallest atom in Group 7 or has the fewest energy levels in Group 7 or has the smallest distance between outer shell and nucleus
fluorine has the least shielding or the greatest attraction between the nucleus and the outer shell therefore fluorine can gain an electron (into the outer shell) more easily Q2.(a) Dmitri Mendeleev was one of the first chemists to classify the elements by arranging them in order of their atomic weights. His periodic table was published in
- How did Mendeleev know that there must be undiscovered elements and how did he take this into account when he designed his periodic table? - ANSWERS.(a) if placed consecutively, then elements would be in wrong group / have wrong properties left gaps 2 (b) By the early 20th century protons and electrons had been discovered. Describe how knowledge of the numbers of protons and electrons in atoms allow chemists to place elements in their correct order and correct group. - ANSWERS(b) (elements placed in) atomic / proton number order (elements in ) same group have same number of outer electrons any one from:
- number of protons = number of electrons
- reactions/(chemical) properties depend on the (outer) electrons
- number of shells gives the period 2 (c) The transition elements are a block of elements between Groups 2 and 3 of the periodic table. (i) Transition elements have similar properties. Explain why, in terms of electronic structure. - ANSWERS(c) (i) (transition elements usually) have same / similar number of outer / 4th shell electrons (because) inner (3rd ) shell / energy level is being filled 2c (ii) There are no transition elements between the Group 2 element magnesium and the Group 3 element aluminium. Give a reason why, in terms of electronic structure. - ANSWERS(ii) 2nd shell / energy level can (only) have maximum of 8 electrons or 2nd shell / energy level cannot have 18 electrons 3b (ii) Mendeleev was able to make predictions about the undiscovered elements. This eventually led most scientists to accept his table. Suggest what predictions Mendeleev was able to make about these undiscovered elements. [2] - ANSWERS(ii) predicted they were metals predicted their (chemical/physical) properties / reactivity
Explain, in terms of electrons, why chlorine is more reactive than bromine. [3] - ANSWERSchlorine atom is smaller than bromine atom or chlorine atom has fewer shells than bromine atom outer shell / energy level of chlorine has stronger (electrostatic) attraction to the nucleus than bromine or outer shell of chlorine is less shielded from the nucleus than bromine so chlorine more readily gains an extra electron Q6. (a) Dimitri Mendeleev was one of the first chemists to classify the elements by arranging them in order of their atomic weights. His periodic table was published in
How did Mendeleev know that there must be undiscovered elements and how did he take this into account when he designed his periodic table? [2] - ANSWERS(a) left gaps if placed consecutively, then elements would be in wrong group / have wrong properties / owtte 6 (b) By the early 20th century protons and electrons had been discovered. Describe how this discovery allowed chemists to place elements in their correct order and correct group. [3] - ANSWERS(b) (elements placed in) atomic / proton number order (elements in) same group have same number of outer electrons
- number of protons = number of electrons
- reactions (chemical) properties depend on the (outer) electrons
- number of shells gives the period 6 (c) The transition elements are a block of elements between Groups 2 and 3 of the periodic table. (i) Transition elements have similar properties. Explain why in terms of electronic structure. - ANSWERS(c) (i) (transition elements usually) have same / similar number of outer / 4th shell electrons inner (3rd ) shell / energy level is being filled 7 (c) Lithium, sodium and potassium are in Group 1. All these elements react with water. Describe what you see when potassium is added to water. - ANSWERS(c) any two from:
- fizzes / bubbles / gas
- violent / vigorous / explodes / very fast reaction
- floats / on surface
- moves (very quickly)
- melts (into a ball)
- bursts into flame
- gets smaller / (reacts to) form a solution / dissolves / disappears etc
- steam / gets hot (owtte) 7 (d) In terms of electronic structure, explain why: (i) elements in the same group of the periodic table have similar chemical properties - ANSWERS(d) (i) same number of electrons in outer shell 7 (d) In terms of electronic structure, explain why: (ii) transition elements have similar properties even though they are not in the same group - ANSWERS(ii) electrons fill an inner / 3rd shell (usually) same number of outer / 4th shell electrons 7 (d) In terms of electronic structure, explain why: (iii) in Group 1, lithium is less reactive than potassium. - ANSWERSouter shell electron closer to nucleus more (electrostatic) attraction (to nucleus) / electrons less likely to be lost 4a Which metal in the table should be used to make the wire in a filament lamp? Give a reason for your answer. - ANSWERS(a) tungsten has the high(est) melting point 4b Which gas in the table should be used in a filament lamp? Give a reason for your answer. - ANSWERSb) argon is an unreactive gas Q5. The properties of transition metals make them useful elements. (a) Why is copper used for electrical wiring? - ANSWERS(a) (good)conductor of electricity 5 b) Why is iron used for girders in buildings? - ANSWERS(b) strong 5 c) Why are transition metal compounds added to glazes for pottery? - ANSWERS(c) reference to colour Q2. Sodium is a Group 1 element. (a) (i) A small piece of sodium is added to some water containing Universal Indicator solution. Describe what you would see happening. [3] - ANSWERS(a) (i) UI / solution turns blue / purple
Explain why Stage 2 needs to be done - separating the ore into the metal compound. - ANSWERS(a) The ore is not pure or contains impurities or the ore does not contain 100% of the metal compound rock / other compounds need to be removed / separated 1 (b) Cast iron from a blast furnace contains 96% iron and 4% carbon. (i) Cast iron is not suitable for the manufacture of pylons. Give one reason why. - ANSWERS(b) (i) (cast iron is) brittle 1b (ii) Most cast iron is converted into steel, as shown in Figure 3 Describe how cast iron is converted into steel. Use Figure 3 to help you to answer this question. - ANSWERS(ii) the oxygen reacts with carbon reducing the percentage of carbon in the mixture or producing carbon dioxide 1 (c) Aluminium and copper are good conductors of electricity. (i) State one property that makes aluminium more suitable than copper for overhead cables. - ANSWERS(c) (i) aluminium has a low density 1c (ii) How can you tell that copper is a transition metal and aluminium is not a transition metal from the position of each metal in the periodic table? - ANSWERS(ii) (because copper) is in the central / middle (block of the periodic table) whereas aluminium is in Group 3 (of the periodic table) 1c (iii) Copper can be extracted from solutions of copper salts by adding iron. Explain why. - ANSWERS(iii) iron is more reactive (than copper) ignore cost so copper is displaced / reduced Q2. The extract below was taken from a leaflet on the uses of platinum. One of the uses described was in making electrodes for spark plugs in car engines. The spark plug produces the spark which ignites the fuel in the engine Spark Plugs The electrodes in a spark plug have to conduct electricity very well. Since they project into the combustion chamber of the engine, they must also be able to withstand extremely high temperatures in a very corrosive atmosphere. Nickel-based plugs have been produced for many years. They only last a fairly short time. As the electrodes wear, combustion becomes less efficient and the petrol is not burnt completely. Platinum and other precious metals can now be used in spark plugs. These last much longer and are more efficient. This can help to reduce air pollution.
(a) Compare nickel and platinum for use in making the electrodes in spark plugs. A good answer should give advantages - ANSWERSAdvantages of Nickel: Relatively low cost which makes the sparking plugs cheaper to produce. Quite high melting point which is needed because the temperature in the engine is very high. Good conductor of electricity needed to carry electricity into combustion chamber to produce spark. Disadvantages of Nickel: Subject to corrosion in engine which means they only last a short time because nickel is higher in reactivity than platinum. Idea that this leads to reduced efficiency, unburnt petrol and air pollution. Advantages of Platinum: Less susceptible to corrosion (not corroded) because platinum is very low in reactivity. Idea that this improves efficiency and reduces pollution.- Higher melting point than nickel to withstand the high temperatures in the combustion chamber. Last a lot longer than nickel electrodes due to low reactivity. Good conductor of electricity as for nickel. Extension here could be linked to the idea that the conductivity does not deteriorate as quickly as nickel.) 2 (b) (i) Describe the structure and bonding in metals. [3] - ANSWERS(b) (i) giant structure/lattice/regular arrangements of atoms of atoms/of ions (provided free electrons mentioned) delocalised or free electrons
