Atomic Structure & The Periodic Table (WJEC GCSE Chemistry)

The diagram shows an atom of element X.

Draw the electronic structure of the element directly below element X in the Periodic Table.

The table below shows information about particles A-F.

The letters A-F are not the chemical symbols of the particles.

i) Give the letters of two particles which are isotopes of the same element.

Explain your answer.

[2]

Letters ........................... and ..............................

ii) Give the letters of two particles which are ions. Explain your answer.

[2]

Letters ............................. and ...........................

S and T are two metal halide compounds. The ions in each compound were identified by observations from a flame test and the addition of silver nitrate solution.

i) Complete the table.

[4]

ii) Suggest why a silver nitrate test would not be able to distinguish clearly which halide ions are present in a mixture of compounds S and T.

[1]

Write an ionic equation for the formation of the precipitate in the reaction between sodium chloride solution and silver nitrate solution.

Include state symbols.

................................ + .......................... → ...............................

This question is about the development of the Periodic Table.

In 1890, not all the elements had been discovered. A Russian scientist named Dmitri Mendeleev used the reactions of the known elements and their relative atomic masses to arrange them in the following table.

Based on the properties of the known elements, he predicted that new elements would be discovered and left gaps for these in his table. He even predicted what the properties of these undiscovered elements would be. He gave the name ekasilicon to one of them. The element that fits into this gap was eventually discovered and named germanium.

Comparison of the properties of ekasilicon and germanium

The modern day Periodic Table is based on Mendeleev’s original table

i) Put a tick (✓) in the correct column to show whether the following statements apply to Mendeleev’s table only, today’s table only or to both tables.

[2]

ii) Tick (✓) the two statements that best describe why germanium was confirmed to be the element ekasilicon predicted by Mendeleev.

[1]

i) Calculate the percentage of oxygen present in the formula of germanium oxide, GeO₂.

[2]

A_r (Ge) = 73                                        A_r (O) = 16

Percentage = ………..................... %

ii) When germanium oxide reacts with hydrochloric acid it produces germanium chloride and water.

Balance the following equation for the reaction that takes place.

[1]

GeO₂ +  HCl  GeCl₄ +  H₂O

Higher Tier Only

The following table shows some information about Group 1 elements. 

i) Describe the trend in density going down the group.

[1]

ii) Explain the difference in reactivity down the group in terms of electronic structure.

[2]

The apparatus below can be used to demonstrate the reaction between sodium and chlorine.

i) Apart from the use of safety goggles, state one safety precaution that needs to be followed when using each of these elements.

[2]

ii) Complete and balance the symbol equation for the reaction that takes place between sodium and chlorine.

[2]

Na + Cl₂  ………....

The following diagram is an outline of the Periodic Table.

Write letters A, B and C on the diagram in the positions of the elements that fit the following descriptions.

 A the element with the electronic structure shown above

 B the element in Group 2 and Period 4

 C an element that shows both metallic and non-metallic properties

The following table shows the atomic numbers and boiling points of the inert gases.

i) Plot this data on the grid opposite. Draw a suitable line.

[3]

ii) Describe the trend in boiling point shown on the graph.

[1]

The following table shows the boiling points of the inert gases in both °C and K.

Use the information in the table to calculate the boiling point of argon in K.

Boiling point = ......................................... K

Give one use of argon. Explain in terms of electronic structure why it is used for this purpose.

The diagrams show the atoms of four elements, A-D.

These letters are not the chemical symbols for the elements.

i) Use the letters A-D to complete the following sentences.

[2]

Two atoms found in the same group are ........................ and ........................ .

The atom found in Group 1 is ........................ .

ii) I      Give the electronic structure of atom B. ………................................................

[1]

II     Give the atomic number of atom B. ………...............................................

[1]

The following diagram shows an atom of lithium.

i) Complete the following sentences.

[2]

Particle X is an ………............................................... .

Particle Y found in the nucleus is a ………............................................... .

ii) Use the diagram to explain why lithium has a mass number of 7.

[1] 

Dafydd was asked to make some silver chloride. He formed a white precipitate of silver chloride by mixing solutions of sodium chloride and silver nitrate.

i) Complete the symbol equation for this reaction.

[1]

NaCl + AgNO₃ ................................................ + ................................................

ii) Put a tick (✓) in the box next to the statement which describes why this method works.

[1]

iii) Give the name of the process that you would use to separate the precipitate of silver chloride from the reaction mixture.

[1]

Calculate the relative formula mass (M_r) of silver nitrate, AgNO₃.

A_r (O) = 16                A_r (N) = 14                    A_r (Ag) = 108

M_r = ...............................

The relative formula mass (M_r) of sodium chloride, NaCl, is 58.5.

Calculate the percentage of sodium in sodium chloride. Give your answer to 1 decimal place.

A_r (Na) = 23

Percentage = ....................................................... %

The following diagram shows an outline of the Periodic Table.

The letters shown are NOT the chemical symbols of the elements

i) Give the group and period of the element labelled C.

[2]

Group . . . . . . . . . . . . . . . . . . .         Period . . . . . . . . . . . . . . . . . . . . .

ii) Give the letter of the element which has both metallic and non-metallic properties.

Give the reason for your choice.

[2]

Letter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

i) The chemical formula of aluminium nitrate is Al(NO₃)₃. Give the number of nitrogen atoms in the formula Al(NO₃)₃.         

[1]

ii) Give the chemical formula of lithium carbonate.

[1]

The bar charts below show the melting points and boiling points of Group 7 elements.

Use the information in the bar charts to answer parts (a)-(d).

Describe the trend, if any, in the melting point going down the group.

Name the element which has the lowest melting point.

Using the same key, draw bars on the grid above to predict the approximate values for the melting point and boiling point of astatine.

Give the name of the element which is liquid at −70 °C.

The following diagrams show the electronic structures of five different elements, A–E.

State which elements, A–E, are found in Period 2 of the Periodic Table.

Give a reason for your choice.

State which element, A–E, has an atomic number of 15. Give a reason for your answer.

Aluminium can be represented as 

State what this tells you about the structure of its atoms.

Sodium bromide is formed by reacting sodium with bromine, Br₂.

Write the balanced symbol equation for the reaction.

.............................. + .............................. → .............................. 

A scientist has solid samples of sodium chloride and sodium iodide but is not sure which is which.

Describe how silver nitrate solution could be used to distinguish between them.

Give the observations expected for both substances.

During a chemical reaction, aluminium combines with chlorine to produce aluminium chloride, AlCl₃.

2Al    +      Cl₂               AlCl₃

i) Balance the equation.

[1]

ii) Calculate the percentage of chlorine present in aluminium chloride, AlCl₃.

[3]

A_r(Al) = 27                       A_r(Cl) = 35.5

 Percentage chlorine = . . . . . . . . . . . . . . . . . .  %

Electrolysis can be used to extract aluminium from its oxide. The equation for the reaction is as follows.

2Al₂O₃       4Al     +    3O₂

204 tonnes of aluminium oxide are expected to produce 108 tonnes of aluminium. However, only 81 tonnes are actually made.

i) Calculate the percentage yield of this process.

[1]

Percentage yield = . . . . . . . . . . . . . . . . . . .%

ii) Suggest reasons why the actual amount produced was lower than expected.     

[2]

Higher Tier Only

An experiment was carried out to determine the trend in reactivity of the halogens. The following table shows the results obtained when solutions of halogens were added to different halide solutions.

i) Use the results in the table to give the order of reactivity of the halogens.

Explain your answer.

[3]

ii) Write the balanced symbol equation for the reaction that takes place between chlorine and potassium iodide.

[3]

.............................. + .............................. → .............................. + ..............................

Higher Tier Only

When silver nitrate solution is added to a solution of potassium bromide, a creamy precipitate of silver bromide is formed. The following reaction takes place.

AgNO₃ (aq) + KBr (aq) → AgBr (s) + KNO₃ (aq)

Calculate the mass of silver nitrate needed to form 47 g of silver bromide. 

A_r (Ag) = 108      A_r (N) = 14      A_r (O) = 16      A_r (Br) = 80

Mass of silver nitrate = .............................. g

The following key shows how to identify some negative ions.

Give the meaning of the term precipitate.

Name the gas given off when identifying CO₃^2– ions.

Substance X was known to be sodium iodide, potassium iodide or potassium bromide.

i) State how a flame test could be used to decide whether substance X is a sodium or a potassium compound.

[2]

ii) Describe how you would carry out a test to show whether X is potassium iodide or potassium bromide. Include the expected observations.

[2]

iii) Give the word equation for the reaction between silver nitrate and potassium bromide.

[1]

............... + ...............    ................. + .................

The following diagrams show the electronic structures of five elements, A–E.

i) Give the letter of the element, A–E, that is in Period 2 of the Periodic Table.

Give the reason for your choice in terms of electronic structure.

[2]

Element  .................

Reason  ..................................

ii) Give the letters, A–E, of two elements that are in Group 0 of the Periodic Table.

Give the reason for your choice in terms of electronic structure.

[2]

.................   and   .................

iii) Another element, X, is in the same group as element E but is one place above it.

Draw a diagram of the electronic structure of element X.

[1]

Explain how the electronic structure of element A can be used to determine the number of protons in its nucleus.

A pupil used the following tests to identify unknown compounds A, B, C and D.

These are described as tests 1 to 5 but not necessarily in this order.

The flow charts show the results obtained for each compound.

Deduce which test is which and hence give the names of compounds A, B, C and D.

A .................

B .................

C .................

D .................

Describe the test for sulfate ions in solution. Include the result for your test.

The diagram below shows some reactions of dilute hydrochloric acid.

Give the names of each of the substances A to E.

A  ...................................................

B  ...................................................

C ...................................................

D  ...................................................

E  ...................................................

Potassium reacts vigorously with water.

i) Describe what you would observe when potassium reacts with water.

[3]

ii) During a class demonstration the potassium exploded. Suggest what might have caused this to happen.

[1]

Complete and balance the symbol equation for the reaction between potassium and water. 

2K    +     2H₂O        .................   +   .................

Sodium reacts with oxygen to give sodium oxide.

i) Using the electronic structures below, draw dot and cross diagrams to show the transfer of electrons and the formation of ions that occur as sodium oxide is formed.

[3]

sodium 2,8,1                      oxygen 2,6

ii) Give the electronic structure of the sodium and oxide ions.

[1]

Name the type of structure present in ammonia, NH₃, and explain why ammonia has a low melting point.

When bromine is passed over heated iron wool it glows and forms iron(III) bromide.

Write a balanced symbol equation for the reaction.

.................  +  .................    .................

Name the substance used to test for the presence of bromide ions in iron(III) bromide solution and give the expected result.

The following box contains the names of six ionic compounds.

State which of the compounds in the box you would expect to

i) give a yellow flame in a flame test,

[1]

ii) produce bubbles when reacting with hydrochloric acid.

[1]

A student has two colourless solutions in unlabelled bottles. He knows that one is potassium chloride and that the other is potassium iodide. Describe a test that could be carried out to distinguish between the solutions, giving the observations expected in both cases.

Compounds containing ammonium ions can be identified by heating gently with sodium hydroxide solution and testing the gas produced.

Name the gas produced and describe how you would positively identify this gas.

Iron(III) chloride solution produces a brown precipitate when it reacts with sodium hydroxide solution.

Write a balanced ionic equation for this reaction. You should include state symbols.

.............................. + .............................. .............................. 

The bar graph shows the densities of five Group 1 metals.

Draw a straight line on the bar graph showing the general trend in density of Group 1 metals. How does your trend line suggest that potassium and not sodium is the anomalous density value?

Higher tier only

The flow chart shows some reactions of Group 1 metals.

i) State and explain one similarity and one difference you would see when lithium and potassium are added separately to a trough of cold water. [4] Similarity ......................................................................... Difference .......................................................................

ii) Write a balanced symbol equation to show the reaction between lithium and oxygen.

[3]

iii) The boxes show some of the elements in Group 1 and Group 7. Explain, in terms of electronic structure, why potassium and chlorine would react the most violently.

[3]

Higher Tier Only

Tables A, B, C and D show the results recorded by four different groups in a class investigating the reactivity of Group 7 elements (the halogens).

Each group added iodine, bromine and chlorine to solutions of sodium halides.

A tick (✓) indicates when a reaction took place and a cross (×) indicates no reaction. Only one table shows the expected results for this experiment.

Table A

Table B

Table C

Table D

i) Give the letter of the table which shows the expected results for this experiment. Explain why these are the expected results.

[3]

Letter ...............................

ii) Write a balanced symbol equation for the reaction between chlorine, Cl₂, and sodium iodide solution.

[3]

Higher Tier Only

A sample of iron bromide with a mass of 37.0 g contains 7.0 g of iron. Find the simplest formula of the iron bromide.

You must show your working.

A_r (Fe) = 56     A_r (Br) = 80

Simplest formula ............................

Higher Tier Only

Potassium has three stable isotopes – , and .

i) Compare the nuclei of each of these isotopes.                                                     

[1]

ii) Use the information to calculate the relative atomic mass, A_r, of potassium.

Record your answer to three significant figures.                                                  

[3]

A_r =

A_r =  . . . . . . . . . . . . . . . . . . . . . .

Lithium lies above potassium in the Periodic Table.

i) Give two similarities and two differences between the reactions of potassium and lithium with water.

[2]

ii) Write a balanced symbol equation for the reaction between potassium and water.

[3]

A student is investigating the relative reactivities of the halogens using the elements and solutions of their halides. She adds each halogen to separate solutions of the other halides.

State and explain the observations made. How can the results be used to determine the relative reactivities of the halogens? Include equations in your answer. 

Higher Tier Only

Group 7 elements are known as the halogens. The following table shows the observations made when the first three members of the group react with hydrogen.

i) Use your knowledge of electronic structure to explain why all the halogens react in a similar way and why they react more slowly on going down the group.

[3]

ii) Hydrogen fluoride is highly corrosive and can be used to etch glass which is mainly silicon dioxide.

Balance the symbol equation for the reaction between hydrogen fluoride and silicon dioxide.

[1]

 HF + SiO₂    SiF₄ +  H₂O

iii) Calcium fluoride reacts with sulfuric acid, H₂SO₄, to produce calcium sulfate and hydrogen fluoride. Give the symbol equation for the reaction.

[3]

Higher Tier Only

Chlorine reacts with aluminium to produce aluminium chloride.

A sample of aluminium chloride of mass 26.70 g was found to contain 5.45 g of aluminium.

Calculate the simplest formula of this chloride of aluminium.

You must show your working.

A_r (Al) = 27              A_r (Cl) = 35.5

 Formula ...........................................................

You have been given three gases, A, B and C. The gases are carbon dioxide, hydrogen and oxygen, but not necessarily in that order.

Describe the tests for carbon dioxide, hydrogen and oxygen and plan a method to identify gases A, B and C without using all three tests.

When a mixture of sodium hydroxide solution and ammonium chloride is heated a gas is given off.

i) Name the gas. .................

[1]

ii) Describe a test you could carry out to identify the gas.

[2]

An atom of element E is represented as follows.

State and explain what information this gives you about element E.

You may wish to refer to the key on the Periodic Table to help you answer this question.

Describe how reactions involving chlorine, bromine and iodine can be used to show the trend in reactivity in Group 7 elements. 

You should include equations in your answer.

i) The table below shows results of tests carried out on three white Group 1 compounds, A, B and C.

The flame tests were carried out on solids and the silver nitrate tests on solutions of the compounds.

Use the information in the table to identify the compounds.

Compound A ........................................................................................................................

Compound B ........................................................................................................................

Compound C ........................................................................................................................

[2]  

ii) The symbol equation represents the reaction occurring between solutions of silver nitrate and magnesium chloride.

2AgNO₃ (aq) + MgCl₂ (aq)   →  Mg(NO₃)₂ (aq) + 2AgCl (s)

Write the ionic equation for the reaction. Include state symbols in your answer.

[3]

W, X, Y and Z represent the halogens fluorine, chlorine, bromine and iodine, but not necessarily in that order.

The diagrams below show some reactions of halogens W and X.

Use the information to identify halogens W, X, Y and Z. 

   W ......................................................................

   X .......................................................................

   Y .......................................................................

   Z .......................................................................

Iron wool burns in fluorine to give iron(III) fluoride.

Write a balanced symbol equation for this reaction.

A student was asked to identify the ions present in three different solutions of compounds, A, B and C.

The student's results from a series of tests on each solution are shown in Table 1.

Table 1

Identify the two ions present in each of the compounds A, B, and C.

A: ____________________ and ____________________ 

B: ____________________ and ____________________ 

C: ____________________ and ____________________ 

Explain why nitric acid is used before using silver nitrate instead of hydrochloric acid or sulfuric acid.

This question is about Group 1 metals.

The reaction between three Group 1 metals, lithium, sodium and potassium, with water was demonstrated by a teacher.

The teacher added a few drops of universal indicator to water in a trough. They then dropped a small piece of the Group 1 metal into the water.

Write the balanced symbol equation for the reaction between lithium and water.

In terms of electronic structure, state and explain the difference in reactivity between potassium and water compared with lithium and water.

State what colour the universal indicator turned when potassium was added to water and explain why it changes to this colour.