The Periodic Table

28 Grade 10 Chemistry questions on The Periodic Table, with worked marking schemes. 28 questions are available on this topic in full.

1. Question 1

   1 mark

   An atom of element X has the electron arrangement 2.8.6. To which group and period does X belong?

   A. Group II, Period 3

   B. Group III, Period 6

   C. Group VI, Period 3

   D. Group VI, Period 4

   (1 mark)

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2. Question 2

   4 marks

   State four ways in which the physical properties of the Group I elements differ from those of the Group VII elements.

   (4 marks)

   Marking scheme

   Any four of the following, 1 mark each: Group I elements are all solids at room temperature, while Group VII elements occur as a gas (chlorine), a liquid (bromine) and a solid (iodine). Group I elements are good conductors of heat and electricity, while Group VII elements are poor conductors. Group I elements are shiny and malleable, while the solid Group VII elements are dull and brittle. Group I elements have a giant metallic structure, while Group VII elements exist as simple diatomic molecules. Group I elements are grey and lustrous when freshly cut, while Group VII elements are distinctly coloured (greenish-yellow, red-brown, dark grey).

3. Question 3

   4 marks

   A learner added chlorine water to a colourless solution of potassium iodide in a boiling tube. (a) State the observation made. (1 mark) (b) Write an equation for the reaction that takes place. (1 mark) (c) Explain the observation in terms of the positions of chlorine and iodine in Group VII. (2 marks)

   (4 marks)

   Marking scheme

   (a) The colourless solution turns brown or yellow-brown; a dark grey or black solid may be deposited - 1 mark. (b) Cl2$(aq)+2KI$(aq) gives 2KCl(aq) + I2(s) - 1 mark (accept the ionic equation Cl2$(aq)+2I-(aq)$ gives $2Cl-(aq)+I$2(s); balanced equation required). (c) Chlorine is higher in Group VII, so its atom is smaller and its outermost energy level is less shielded from the nucleus - 1 mark. Chlorine therefore gains an electron more readily than iodine and displaces iodine from its salt - 1 mark.

4. Question 4

   1 mark

   Which of the following period 3 elements is the best conductor of electricity?

   A. silicon

   B. sodium

   C. aluminium

   D. phosphorus

   (1 mark)

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5. Question 5

   1 mark

   Which pair of elements, whose electron arrangements are given below, belongs to the same group of the periodic table?

   A. 2.8.7 and 2.8.8

   B. 2.8.4 and 2.8.8

   C. 2.8.1 and 2.8.2

   D. 2.6 and 2.8.6

   (1 mark)

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6. Question 6

   2 marks

   Explain why the chloride ion, Cl-, is larger than the chlorine atom, Cl.

   (2 marks)

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7. Question 7

   1 mark

   Welders in a jua kali yard use a stream of argon gas around the hot metal they are joining. Argon is chosen because:

   A. argon dissolves the oxide layer already present on the metal surface

   B. argon is denser than air and therefore presses the flame onto the metal

   C. argon has a very high boiling point and so does not escape from the hot joint

   D. argon has a full outermost energy level and therefore does not react with the hot metal

   (1 mark)

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8. Question 8

   1 mark

   Silicon melts at a much higher temperature than phosphorus, although the two elements are neighbours in period 3. This is because:

   A. silicon has a larger atomic radius than phosphorus, so its bonds are stronger

   B. silicon atoms have a greater mass than phosphorus atoms

   C. silicon has a giant covalent structure, while phosphorus exists as simple molecules with weak forces between them

   D. silicon is a metal, while phosphorus is a non-metal

   (1 mark)

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9. Question 9

   2 marks

   Explain why the noble gases have very low boiling points.

   (2 marks)

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10. Question 10

    1 mark

    Across period 3, from sodium to chlorine, the atomic radius decreases. The best explanation for this is that:

    A. the added electrons repel one another and pull the energy levels inwards

    B. the number of occupied energy levels decreases from sodium to chlorine

    C. the relative atomic mass increases, so the atoms become denser and therefore smaller

    D. the nuclear charge increases while the added electrons enter the same energy level

    (1 mark)

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11. Question 11

    3 marks

    An element K has atomic number 19. (a) Write the electron arrangement of an atom of K. (1 mark) (b) State the group and the period to which K belongs, giving a reason for each. (2 marks)

    (3 marks)

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12. Question 12

    4 marks

    Element Q has the electron arrangement 2.8.3 and element R has the electron arrangement 2.6. (a) State the type of bond formed when Q reacts with R. (1 mark) (b) Write the formula of the compound formed. (1 mark) (c) State two physical properties you would expect of this compound. (2 marks)

    (4 marks)

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13. Question 13

    3 marks

    Silicon is the main material used in the solar panels installed on rooftops in Garissa. Explain why silicon is described as a metalloid.

    (3 marks)

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14. Question 14

    3 marks

    Explain why magnesium has a higher melting point than sodium.

    (3 marks)

    Marking scheme

    Each magnesium atom releases two electrons into the sea of delocalised electrons while each sodium atom releases only one - 1 mark. The magnesium ion is smaller and carries a charge of 2+ compared with the larger 1+ sodium ion - 1 mark. The electrostatic attraction between the ions and the delocalised electrons is therefore stronger in magnesium, so more heat energy is needed to melt it - 1 mark.

15. Question 15

    3 marks

    When potassium is heated in sulphur vapour, potassium sulphide is formed. Potassium is in Group I and sulphur is in Group VI. Explain how the potassium ion and the sulphide ion are formed from their atoms.

    (3 marks)

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16. Question 16

    3 marks

    (a) State what is meant by the atomic radius of an element. (1 mark) (b) Explain why the atomic radius increases on going down Group I, from lithium to caesium. (2 marks)

    (3 marks)

    Marking scheme

    (a) Half the distance between the nuclei of two atoms of the same element joined together - 1 mark (accept: the distance from the nucleus to the outermost energy level of the atom). (b) Each element down the group has one more occupied energy level than the one above it, so the outermost electrons lie further from the nucleus - 1 mark. The shielding of the outermost electrons by the inner energy levels also increases down the group, so the nucleus holds them less firmly and the atom is larger - 1 mark.

17. Question 17

    1 mark

    The sodium ion, Na+, is smaller than the sodium atom, Na. Which statement explains this difference in size?

    A. The ion has lost a proton, so its nucleus is smaller

    B. The ion carries a positive charge, and positively charged particles are always smaller than neutral ones

    C. The ion has one energy level fewer than the atom, and the same nuclear charge holds the remaining electrons more tightly

    D. The ion has gained an electron, so the outermost energy level is pulled closer to the nucleus

    (1 mark)

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18. Question 18

    1 mark

    A small piece of calcium metal was dropped into cold water in a beaker. What would be observed?

    A. the metal melts into a silvery ball that darts about on the surface of the water

    B. no change, because calcium reacts with steam only and not with cold water

    C. steady effervescence, and the water slowly turns milky as a white suspension forms

    D. a brown solid is deposited and the water turns brown

    (1 mark)

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19. Question 19

    1 mark

    Element R has the electron arrangement 2.8.2 and element T has the electron arrangement 2.8.7. What is the formula of the compound formed between R and T?

    A. R2T7

    B. RT2

    C. RT

    D. R2T

    (1 mark)

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20. Question 20

    3 marks

    Account for the fact that aluminium oxide reacts with and dissolves in both dilute hydrochloric acid and sodium hydroxide solution.

    (3 marks)

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21. Question 21

    1 mark

    In the modern periodic table, the elements are arranged in order of increasing:

    A. atomic number

    B. relative atomic mass

    C. melting point

    D. number of neutrons in the nucleus

    (1 mark)

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22. Question 22

    3 marks

    Potassium and sodium are both stored under paraffin. Explain why potassium reacts more vigorously with cold water than sodium does.

    (3 marks)

    Marking scheme

    The outermost electron of potassium is in the fourth energy level while that of sodium is in the third, so it is further from the nucleus - 1 mark. Potassium has more inner energy levels shielding the outermost electron, so the attraction of the nucleus for it is weaker - 1 mark. Potassium therefore loses its outermost electron more easily, so the reaction is faster and more vigorous (the hydrogen produced may ignite with a lilac flame) - 1 mark.

23. Question 23

    1 mark

    Which quantity increases on going down Group II, from beryllium to barium?

    A. the electronegativity

    B. the atomic radius

    C. the number of electrons in the outermost energy level

    D. the first ionisation energy

    (1 mark)

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24. Question 24

    5 marks

    Sodium oxide and sulphur(IV) oxide were each shaken separately with distilled water. (a) State the effect of each of the two solutions formed on litmus paper. (2 marks) (b) Explain the difference in terms of the positions of sodium and sulphur in period 3. (2 marks) (c) State the general trend in the nature of the oxides of the elements across period 3. (1 mark)

    (5 marks)

    Marking scheme

    (a) The sodium oxide solution turns red litmus paper blue, showing it is alkaline - 1 mark. The sulphur(IV) oxide solution turns blue litmus paper red, showing it is acidic - 1 mark. (b) Sodium is a metal on the left of the period and its oxide is ionic, so it reacts with water to give an alkaline hydroxide - 1 mark. Sulphur is a non-metal on the right of the period and its oxide is molecular (covalent), so it dissolves to give an acidic solution - 1 mark. (c) The oxides change from basic on the left, through amphoteric in the middle, to acidic on the right - 1 mark.

25. Question 25

    3 marks

    (a) State what is meant by the first ionisation energy of an element. (1 mark) (b) Explain why the first ionisation energy of sodium is lower than that of magnesium. (2 marks)

    (3 marks)

    Marking scheme

    (a) The energy required to remove one electron from each atom in one mole of gaseous atoms of the element - 1 mark. (b) Magnesium has 12 protons against the 11 of sodium, so it has the greater nuclear charge with the same number of occupied energy levels - 1 mark. The magnesium atom is therefore smaller and holds its outermost electron more firmly, so more energy is needed to remove it - 1 mark.

26. Question 26

    1 mark

    The melting points of the Group I metals decrease from lithium to caesium. The best explanation for this trend is that, on going down the group:

    A. the nuclear charge increases, so the metal ions repel one another more strongly

    B. the atomic radius increases, so the attraction between the metal ions and the delocalised electrons becomes weaker

    C. the metals become softer, and soft substances always melt at low temperatures

    D. each atom releases fewer electrons into the sea of delocalised electrons

    (1 mark)

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27. Question 27

    1 mark

    Elements placed in the same group of the periodic table have similar chemical properties because their atoms have the same:

    A. number of electrons in the outermost energy level

    B. number of occupied energy levels

    C. number of neutrons in the nucleus

    D. relative atomic mass

    (1 mark)

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28. Question 28

    1 mark

    Sodium metal, used in the manufacture of some of the chemicals handled at Magadi, is kept under paraffin oil in the laboratory because:

    A. sodium reacts rapidly with oxygen and moisture in the air, and the paraffin keeps air away

    B. sodium dissolves in water vapour to form an acid that corrodes the container

    C. sodium is a soft metal that would otherwise crumble into powder

    D. the paraffin cools the sodium and prevents it from melting at room temperature

    (1 mark)

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