Particles and Periodic Table

Transcription

1 Specification points Year 9 Particles The three states of matter The three states of matter are solid, liquid and gas. In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions. Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point. The three states of matter can be represented by a simple model. In this model, particles are represented by small solid spheres. Particle theory can help to explain melting, boiling, freezing and condensing. The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance. Students should be able to: predict the states of substances at different temperatures given appropriate data explain the different temperatures at which changes of state occur in terms of energy transfers and types of bonding recognise that atoms themselves do not have the bulk properties of materials Explain the limitations of the particle theory in relation to changes of state when particles are represented by solid inelastic spheres which have no forces between them. Year 9 Atomic Structure and the Periodic Table Models of the atom The plum pudding model suggested that the atom was a ball of positive charge with negative electrons embedded in it. Rutherford and Marsden s alpha scattering experiments led to the plum pudding model being replaced by the nuclear model. Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. Later experiments led to the idea that the nucleus has a positive charge particle called a proton. In 932 the experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. Students should be able to: recognise that the model for the structure of the atom developed. describe the plum pudding model and nuclear model of the atom describe why evidence from the scattering experiment led scientists to move from the plum pudding model of the atom to the nuclear model. Atoms, elements and compounds There are about 00 different elements shown on the Periodic Table. A compound is where two or more elements are chemically combined in fixed proportions. Use the names and symbols of the first 20 elements in the periodic table, the elements in Groups and 7, and other elements in the course. Students should be able to: Particles and Periodic Table name compounds of these elements from given formulae or symbol equations write word equations for the reactions in this specification write formulae and balanced chemical equations for the reactions in this specification. know the electrical charges and masses of protons, neutrons and electrons. know that the atomic number is the number of protons

2 In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms of different elements have different numbers of protons. Atoms are very small, having a radius of about 0. nm ( x 0-0 m). The radius of a nucleus is less than /0 000 of the atom (about x 0-4 m). Almost all of the mass of an atom is in the nucleus. Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element. Students should be able to calculate the numbers of protons, neutrons and electrons in an atom or ion, given its atomic number and mass number. Electronic structure The electrons in an atom occupy the lowest available energy levels (innermost available shells). The electronic structure of an atom can be represented by numbers or by a diagram. For example, the electronic structure of sodium is 2,8, or electron configuration diagrams showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level. Year 9 and Year 0 Further Atomic Structure The Periodic Table The elements in the periodic table are arranged in order of atomic (proton) number. Elements with similar properties are in columns, known as groups, elements in a group have the same number of outer shell electrons and this gives them similar chemical properties. The table is called a periodic table because similar properties occur at regular intervals. Students should be able to: explain how the position of an element in the periodic table is related to the arrangement of electrons in its atoms and hence to its atomic number predict possible reactions and probable reactivity of elements from their positions in the periodic table. Development of the periodic table Be able to describe the steps in the development of the Periodic Table: Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of their atomic weights. The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed. Mendeleev left gaps for undiscovered elements and in some places changed the order based on atomic weights. Elements with properties predicted by Mendeleev were discovered and filled the gaps. Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct. Metals and non-metals Metals react to form positive ions whilst non metals ions do not. The majority of elements are metals. Be able to identify the positions of metals and non metals on the periodic table. Students should be able to explain: the differences between metals and non-metals on the basis of their characteristic physical and chemical properties. how the atomic structure of elements relates to their position in the periodic table how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number.

3 Group The Alkali Metals: are low density metals, the first three elements in the group are less dense than water. react with water, releasing hydrogen react with non-metals to form ionic compounds and form + ions. the compounds are white solids that dissolve in water to form colourless solutions form hydroxides that dissolve in water to give alkaline solutions. Increase in reactivity down the group due to increased electron shielding and size. Students should be able to: explain how properties of gp depends on the outer shell electrons of the atoms predict properties from given trends down the group. Group 7 The Halogens The elements in Group 7 are non metals and consist of molecules of pairs of atoms, they react with metals to form ionic compounds in which the halide ion carries a charge of and form molecular compounds with other non-metallic elements. The further down the group an element is the higher its relative molecular mass, melting point and boiling point. The reactivity of the elements decreases going down the group and a more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt. Students should be able to: explain how properties of gp 7 depends on the outer shell of electrons of the atoms predict properties from given trends down the group. Independent Study suggestions. Look at the specification points above ) to make a few notes/spider diagram/revision cards 2. For any area where you feel you need a bit more help have a look at the Fuse School short 3-4 minute explanation video in the Properties of solids, liquids and gases and the atomic structure sections : States of Matter video Brownian motion video Changes of state video: Diffusion of gases Solubility of water Atomic Structure Isotopes Atomic Structure 3 Atomic Mass Atomic Mass and Atomic number: Relative Atomic Mass: Electron Configuration Electron Configuration 2 Electron configuration 3 Shielding Mendeleev and the Periodic Table The lay out of the Periodic Table Groups and Periods in the Periodic Table Group Group Noble Gases : Group 2 :

4 The Halogens Reactions of the halogens Uses of the halogens Trends in the Periodic Table 3. Now have a go at answering the questions below and then using the markschemes to mark them..

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7 Q3. (a) Use the periodic table on the Data Sheet to help you answer these questions. Part of the periodic table is shown below. The letters are not the symbols of the elements. Choose your answers only from the letters shown in the periodic table above. Which letter, A, B, C, D, E or F, represents (5) (i) hydrogen (ii) (iii) a Group 3 element a halogen (iv) the element with atomic (proton) number of 7 (v) an element with one electron in its outer shell? (b) The table shows the melting points of the Group metals arranged in alphabetical order. Group metal Name Symbol Melting point in C Caesium Cs 29 Francium Fr 27 Lithium Li 80 Potassium K 64 Rubidium Rb 39 Sodium Na 98 (i) Arrange these metals in order of increasing melting point. Three have been done for you. Fr Cs Li () (ii) Use the periodic table on the Data Sheet and your answer in part (b)(i) above to complete this sentence about how the melting points change. Going down Group, the melting points... ()

8 (c) The transition metals are a block of elements between Groups 2 and 3 of the periodic table. Transition metals have different properties to Group metals. Put ticks ( ) next to the three correct statements about transition metals in the table below. Statement ( ) They are harder than Group metals They have lower densities than Group metals They have higher melting points than Group metals They are more reactive with water than Group metals They often form coloured compounds but Group compounds are usually white (3) (Total 0 marks) Q4. Sodium is a Group element. (a) (i) A small piece of sodium is added to some water containing Universal Indicator solution. Describe what you would see happening. (3) (ii) Complete and balance the equation for the reaction of sodium with water....na +...H 2 O... + H 2 (2) (b) Francium is the most reactive element in Group. Explain why in terms of electronic structure. (3)

9 (c) The transition elements have different properties from the elements in Group. Give two of these different properties of transition elements (2) (Total 0 marks) Q5.This question is about atomic structure and elements. (a) Complete the sentences. (i) The atomic number of an atom is the number of... () (ii) The mass number of an atom is the number of () (b) Explain why an atom has no overall charge. Use the relative electrical charges of sub-atomic particles in your explanation.. (2) (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. (2)

10 (d) The diagram shows the electronic structure of an atom of a non-metal. What is the chemical symbol of this non-metal? Circle the correct one: Ar O S Si () (e) When elements react, their atoms join with other atoms to form compounds. Complete the sentences. (i) Compounds formed when non-metals react with metals consist of particles called. () (ii) Compounds formed from only non-metals consist of particles called.... () (Total 9 marks) Q6.(a) The symbols for seven different elements are shown in Figure. Figure Be Na S Ar He Ca Fe Choose the correct symbol from Figure to answer each question. You may use each symbol once, more than once or not at all. Write the symbol that represents: (i) a Group element... ()

11 (ii) a transition metal... () (iii) an element with electrons in the same number of energy levels as an atom of argon (Ar)... () (iv) an element which forms an oxide that dissolves in water to form an acidic solution... () (v) an element that forms a chloride with the formula XCl... () (b) A teacher put a cube of sodium metal into water containing universal indicator, as shown in Figure Figure 2 The equation for the reaction is: 2Na(s) + 2H 2 O(l) 2NaOH (aq) + H 2 (g) sodium + water sodium hydroxide + hydrogen (i) The sodium floated on the surface of the water. The universal indicator turned purple. Give three other observations that would be seen during the reaction (ii) Name the ion that made the universal indicator turn purple.... (3) ()

12 (c) Figure 3 represents the electronic structure of a sodium atom. Figure 3 In the space below, draw the electronic structure of a sodium ion. Include the charge on the ion. Q7. The electronic structure of the atoms of five elements are shown in the figure below. The letters are not the symbols of the elements. (2) (Total marks) Choose the element to answer the question. Each element can be used once, more than once or not at all. Use the periodic table to help you. (a) (b) Which element is hydrogen? Which element is a halogen? () () (c) Which element is a metal in the same group of the periodic table as element A? () (d) Which element exists as single atoms? ()

13 (e) There are two isotopes of element A. Information about the two isotopes is shown in the table below. Mass number of the isotope 6 7 Percentage abundance Use the information in the table above above to calculate the relative atomic mass of element A. Give your answer to 2 decimal places. Relative atomic mass =... (4) (Total 8 marks) Q8.This question is about elements and the periodic table. (a) (i) Newlands and Mendeleev both produced early versions of the periodic table. Complete the sentence. In their periodic tables, Newlands and Mendeleev arranged the elements in order of.... (ii) Name the particle that allowed the elements to be arranged in order of their atomic number in the modern periodic table.... () () (b) The diagram below shows the position of nine elements in the modern periodic table.

14 (i) Which one of the nine elements shown in the diagram above has the lowest boiling point?... () (ii) Copper and potassium have different melting points and boiling points. Give one other difference between the properties of copper and potassium. () (iii) Explain why the reactivity of the elements increases going down Group from lithium to rubidium but decreases going down Group 7 from fluorine to iodine. (4) (Total 8 marks) Q9.This question is about halogens and their compounds. The table below shows the boiling points and properties of some of the elements in Group 7 of the periodic table. Element Boiling point in C Colour in aqueous solution Fluorine 88 colourless Chlorine 35 pale green Bromine X orange Iodine 84 brown

15 (a) Why does iodine have a higher boiling point than chlorine? Tick one box. Iodine is ionic and chlorine is covalent Iodine is less reactive than chlorine The covalent bonds between iodine atoms are stronger The forces between iodine molecules are stronger () (b) Predict the boiling point of bromine.... () (c) A redox reaction takes place when aqueous chlorine is added to potassium iodide solution. The equation for this reaction is: Cl 2 (aq) + 2KI(aq) I 2 (aq) + 2KCl(aq) Look at table above. What is the colour of the final solution in this reaction? Tick one box. Brown Orange Pale green Colourless () (d) What is the ionic equation for the reaction of chlorine with potassium iodide? Tick one box. Cl 2 + 2K 2KCl 2I + Cl 2 I 2 + 2Cl I + Cl I + Cl I + K + KI ()

16 (e) Why does potassium iodide solution conduct electricity? Tick one box. It contains a metal It contains electrons which can move It contains ions which can move It contains water () (f) What are the products of electrolysing potassium iodide solution? Tick one box. Product at cathode hydrogen Product at anode iodine hydrogen oxygen potassium iodine potassium oxygen () (Total 6 marks) Q0.There are eight elements in the second row (lithium to neon) of the periodic table. (a) Figure shows a lithium atom. (i) What is the mass number of the lithium atom in Figure?... () (ii) What is the charge of an electron?.. (iii) Protons are in the nucleus. Which other sub-atomic particles are in the nucleus?... () ()

17 (b) What is always different for atoms of different elements? Tick ( ) one box. number of neutrons number of protons number of shells () (c) Figure 2 shows the electron arrangements of three different atoms, X, Y and Z. These atoms are from elements in the second row (lithium to neon) of the periodic table. Which atom is from an element in Group 3 of the periodic table? Tick ( ) one box. Atom X Atom Y Atom Z () (d) Figure 3 shows the electron arrangement of a different atom from an element in the second row of the periodic table. (i) Give the chemical symbol of this element.... ()

18 (ii) Why is this element unreactive? () Q.There are eight elements in the second row (lithium to neon) of the periodic table. (a) Figure shows an atom with two energy levels (shells). (i) Complete Figure to show the electronic structure of a boron atom. () (ii) What does the central part labelled Z represent in Figure?... () (iii) Name the sub-atomic particles in part Z of a boron atom. Give the relative charges of these sub-atomic particles (3) (b) The electronic structure of a neon atom shown in Figure 2 is not correct. Explain what is wrong with the electronic structure shown in Figure (3)

19 ANSWERS Answers: M3. (a) (i) A (ii) F

20 (iii) (iv) (v) E C A or B (b) (i) Rb K Na allow rubidium, potassium, sodium do not accept RB or NA (ii) decrease or become lower / smaller / less allow from 80 C to 27 C (c) They are harder than Group metals. They have higher melting points than Group metals. hey often form coloured compounds but Group compounds are usually white. M4. (a) (i) UI / solution turns blue / purple allow violet / lilac any two from: floats melts / forms a sphere moves note: moves on surface = 2 marks (points and 3) effervescence / fizz / bubbles / gas ignore the name of the gas (yellow) flame ignore sparks / ignites / burns allow dissolves reduces in size ignore reacts violently unqualified ignore reference to exothermic / heat evolved 2 [0] (ii) 2Na + 2H 2O 2NaOH + H 2 correct equation = 2 marks allow correct multiples / fractions if this equation is unbalanced,

21 allow mark for NaOH 2 (b) it = francium outer electron / shell / energy level must be mentioned once for all 3 marks biggest atom or (outer) shell / energy level / electron furthest from nucleus or most (number of) shells least attraction (to nucleus) or most shielding allow the attraction is very weak do not allow less magnetic / gravitational attraction (outer) electron more easily lost / taken ignore francium reacts more easily / vigorously (c) any two from: ignore other properties / specific reactions they / it = transition elements transition elements: allow if state group elements high melting point or high boiling point low melting point or low boiling point high density low density strong / hard weak / soft not very reactive reactive catalysts not catalysts ions have different charges + ions coloured compounds white compounds 2 [0] M5.(a) (i) protons allow protons or electrons, but do not allow protons and electrons (ii) protons plus / and neutrons (b) (because the relative electrical charges are) () for an electron and +() for a proton allow electrons are negative and protons are positive and the number of electrons is equal to the number of protons

22 if no other mark awarded, allow mark for the charges cancel out (c) (the electronic structure of) fluorine is 2,7 and chlorine is 2,8,7 allow diagrams for the first marking point (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 if no other mark awarded, allow mark for have the same / similar properties (d) S (e) (i) ions (ii) molecules [9] M6.(a) (i) Na allow sodium / phonetic spelling if more than one answer is given apply list principle (ii) Fe allow iron / phonetic spelling if more than one answer is given apply list principle (iii) Na or S allow sodium or sulfur / sulphur / phonetic spelling if more than one answer is given apply list principle (iv) S allow sulfur / sulphur / phonetic spelling if more than one answer is given apply list principle (v) Na allow sodium / phonetic spelling if more than one answer is given apply list principle (b) (i) any three from: effervescence / fizzing or bubbles or gas produced do not allow incorrectly named gas sodium melts or turns into a ball sodium moves (on the surface) steam / mist / vapour is produced ignore heat / temperature / flame / spark sodium gets smaller / disappears allow dissolves colour of indicator is darker / more intense near the sodium Must be linked to near the sodium. 3

23 (ii) hydroxide or OH allow OH without a charge do not allow OH + (c) diagram showing electron configuration of ion is 2,8 charge on ion is + Bracket not necessary [2,8] + is worth mark as there is no diagram [] M7.(a) B (b) (c) (d) D E C (e) and allow 6.08 with no working shown for 4 marks [8] M8.(a) (i) atomic weights allow atomic masses (ii) proton allow proton number (b) (i) F/fluorine allow F 2

24 (ii) any one from: copper has a higher density copper is stronger copper is harder copper is less reactive allow named property ignore colour, conductivity, melting point and boiling point allow converse for potassium (iii) relative distance from nucleus allow more / fewer energy levels / shells or larger / smaller atom relative attraction to nucleus allow more / less shielding relative ease of gain or loss of electron opposite explanation of ease of gain or loss of electron for other group max 3 marks if outer not mentioned [8] M9.(a) The forces between iodine molecules are stronger (b) anything in range +30 to +20 (c) Brown (d) 2 I + Cl 2 I Cl (e) It contains ions which can move (f) hydrogen iodine M0.(a) (i) 7 (ii) [6] (iii) (b) (c) neutrons number of protons atom Y (d) (i) Ne allow neon

25 (ii) has a full outer shell allow in Group 0 allow a noble gas or full outer energy level allow the shells are full or has 8 electrons in its outer shell ignore in Group 8 M.(a) (i) electronic structure 2,3 drawn allow any representation of electrons, such as, dots, crosses, or numbers (2,3) [7] (ii) nucleus (iii) protons and neutrons do not allow electrons in nucleus (relative charge of proton) + allow positive (relative charge of neutron) 0 allow no charge/neutral ignore number of particles (b) too many electrons in the first energy level or inner shell allow inner shell can only have a maximum of 2 electrons too few electrons in the second energy level or outer shell allow neon has 8 electrons in its outer shell or neon does not have electron in its outer shell allow neon has a stable arrangement of electrons or a full outer shell neon does not have 9 electrons or neon has 0 electrons allow one electron missing allow fluorine has 9 electrons ignore second shell can hold (maximum) 8 electrons or 2,8,8 rule or is a noble gas or in Group 0 max 2 marks if the wrong particle, such as atoms instead of electrons if no other mark awarded allow mark for the electronic structure of neon is 2,8 [8]