Elements and compounds: Worksheet 1.1 · For example, a compound made from magnesium and oxygen is called magnesium oxide. The name of the metal part does not change, but oxygen is

Chapter 1: Atomic structure and the periodic table

AQA GCSE: Chemistry: Teacher Pack © HarperCollinsPublishers Limited 2016

Elements and compounds: Worksheet 1.1.1

Symbols, elements, compounds and chemical reactions 1. Use your copy of the periodic table to find the chemical symbol for:

a) carbon ________; b) oxygen ________; c) calcium ________; d) copper ________

e) sodium _______ ; f) hydrogen _______; g) potassium ________; h) iron________

2. a) Suggest why the symbol for silicon is Si and not S.

___________________________________________________________________________

b) Most chemical symbols are derived from the English names for the element. Give the names and symbols of four exceptions.

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3. Read this description of two elements reacting together to make a compound.

A piece of clean, grey, shiny sodium metal was heated on a deflagrating spoon until it started to burn. It was then put into a gas jar of chlorine gas. Chlorine gas is green/yellow. The sodium burnt vigorously with a brilliant white light and a white powder was left on the walls of the gas jar.

a) Name the elements. ________________________________________________________

b) Name the compound made. __________________________________________________

c) Which chemical symbols make up the formula of the compound? ______________________

d) What evidence is there that a chemical reaction has taken place?

_________________________________________________________________________

e) How does this description show that new substances are made in chemical reactions?

_________________________________________________________________________

f) What is needed to change the compound back into the elements?

_________________________________________________________________________



Elements and compounds: Worksheet 1.1.2

What’s in a compound? Compounds are named from the elements they are made from. If the compound contains a metal and a non-metal, the metal element is usually listed first and the non-metal last.

For example, a compound made from magnesium and oxygen is called magnesium oxide. The name of the metal part does not change, but oxygen is changed to oxide.

The table shows what some names mean in compounds.

Name used in a compound The compound contains …

Oxide oxygen

Sulfide sulfur

Nitride nitrogen

Chloride chlorine

Bromide bromine

Iodide iodine

1. Complete the table below to show which elements the compounds contain.

Name of compound Elements it contains …

Magnesium oxide

Calcium sulfide

Sodium bromide

Potassium iodide

Lithium oxide

Aluminium chloride

Copper nitride

Copper sulfide

2. These are the formulae for some compounds. Name the compounds and the elements they

contain. a) MgS _____________________________________________________________________

b) FeS _____________________________________________________________________

c) CuO _____________________________________________________________________

d) KI _______________________________________________________________________

e) NaCl _____________________________________________________________________

f) CaO _____________________________________________________________________

g) LiBr _____________________________________________________________________

h) MgO _____________________________________________________________________


Developing the periodic table: Worksheet 1.10.1


7 Lithium reactive metal

75 Arsenic

grey metalloid

24 Magnesium fairly reactive

metal

79 Selenium grey solid

fairly reactive non-metal

16 Oxygen

colourless gas fairly reactive

non-metal

19 Fluorine

yellow gas reactive

non-metal

137 Barium

fairly reactive metal

39 Potassium

reactive metal

11 Boron black

metalloid

? Not

discovered until 1886

12 Carbon

black solid non-metal

80 Bromine

brown liquid reactive

non-metal

35.5 Chlorine green gas reactive

non-metal

23 Sodium reactive metal

32 Sulfur

yellow solid fairly reactive

non-metal

? Not

discovered until 1875

40 Calcium


14 Nitrogen

colourless gas unreactive non-metal

9 Beryllium


28 Silicon silver

metalloid




31 Phophorus

fairly reactive non-metal

127 Iodine

grey solid reactive

non-metal

88 Strontium


27 Aluminium

silver metal




Changing scientific ideas New scientific ideas are more likely to be accepted if they can be used to make predictions that turn out to be correct.

Thomson’s model of the atom had positive charges spread all through it. 1. Explain why this model was refuted by Geiger and Marsden’s scattering experiment.

___________________________________________________________________________ Mendeleev used the patterns and trends he knew about to predict some of the properties of missing elements. He called the element immediately below silicon ‘eka-silicon’. Model Prediction Results

Periodic table Eka-silicon’s properties will fit with the rest of its group e.g. density = 5 g/cm3

Germanium discovered density = 5.32 g/cm3

2. Explain why Mendeleev’s model was supported when germanium was discovered.

___________________________________________________________________________ ___________________________________________________________________________

3. Explain how the discovery of electrons and their arrangement in atoms gave further support to

Mendeleev’s ideas.

___________________________________________________________________________

___________________________________________________________________________



4. Mendeleev worked with atomic weights – what we call ‘atomic masses’. Find two elements in the

periodic table with atomic masses that seem to be in the wrong order.

___________________________________________________________________________

5. What decides the order of the elements in the modern periodic table?

___________________________________________________________________________



Comparing metals and non-metals: Worksheet 1.11

Metal versus non-metal 1 Use the words YES, NO, HIGH and LOW to complete the table below.

Physical property Metal Non-metal

Lustrous

Hard

Density

Tensile strength

Melting or boiling point

Conductor of heat

Conductor of electricity

Metal versus non-metal 2 Use the words YES and NO to complete the table below.

Chemical property Metal Non-metal

Most react with oxygen

Most react with an acid

Their oxides are acidic

Their oxides are basic



Metals and non-metals: Worksheet 1.12.1

Ions When sodium atoms and chlorine molecules react their atoms become charged ions: Sodium, magnesium and aluminium are metals. When their atoms react, they lose their outer electrons. Each electron lost leaves them with one positive charge. 1. Write the symbols for sodium, magnesium and aluminium ions. __________________________ Nitrogen, oxygen and fluorine are non-metals. When their atoms react, they gain electrons to fill their outer shells. Each extra electron gives them one negative charge.

2. Nitrogen forms N3− ions. Write the symbols for oxide ions and for fluoride ions. ______________________

3. Now write the symbols for the ions these atoms will form:

a) lithium ________; b) chlorine ________; c) calcium ________

d) sulfur ________; e) bromine ________; f) potassium ________

flourine

2,8,1 2,8,2 2,8,3

2,5 2,6 2,7



Metals and non-metals: Worksheet 1.12.2

Dot-and-cross diagrams When sodium and chlorine react, sodium’s outer electron is transferred to chlorine’s outer shell. Dot-and-cross diagrams model this process. Models do not need to be exactly like the real thing to be useful. These dot-and-cross diagrams clarify what happens by showing only the outer electrons. Draw simplified dot-and-cross diagrams to show how each of the following ionic compounds form:

1. Potassium fluoride (KF) 2. Magnesium oxide (MgO) 3. Sodium oxide (Na2O) 4. Magnesium chloride (MgCl2)



Key concept: The outer electrons: Worksheet 1.13

.



Exploring Group 0: Worksheet 1.14

The Group 0 elements

These elements don’t react by making ions and don’t make molecules. They have stable electronic structures because they have full outer shells.

1. What is the same about the electronic structures of these elements?

___________________________________________________________________________ 2. What makes helium different from the others?

___________________________________________________________________________

___________________________________________________________________________

3. Explain why none of these gases form ions.

___________________________________________________________________________

___________________________________________________________________________

2,8 2,8,8 2



Atoms, formulae and equations: Worksheet 1.2.1

Find the formula Every compound has a specific formula. Elements in the same group of the periodic table form compounds with similar formulae.

Element 1 group

Element 2 group

Ratio of atoms

Typical formulas

1 7 1 : 1 LiCl 2 6 1 : 1 MgO 2 7 1 : 2 MgCl2 1 6 2 : 1 K2O

Complete the table.

Compound Element 1 Group Element

2 Group Ratio Compound name

Compound formula

a Ca 2 O 6 1 : 1 calcium oxide

b Ca Cl

c Na F

d Be S

e Be F

f Li F

g Mg S

h K Cl

i Mg F

j Li O

k Na O

l Li S




Line up the symbols ... then balance the equation Equations can show how compounds form. To write an equation, first find every symbol and formula. The symbols for elements are in the periodic table. Many gases form molecules so their symbols have a subscript number.

The symbols and formulae below show what happens when magnesium burns:

The equation above is unbalanced. There are more oxygen atoms before the reaction than after. Two magnesium atoms need to react with each pair of oxygen atoms to form two ‘lots’ of magnesium oxide. So the balanced equation looks like this:

The equations below are incomplete. Write the formulae of the compounds formed. Then add any numbers needed to balance the equations (sometimes none may be needed). REMEMBER a balanced equation has the same numbers of the same atoms before and after the reaction.

a) Ca + O2 → ..........................

b) Ca + Cl2 → ...........................

c) Na + F2 → ............................

d) Be + S → .............................

e) Be + F2 → ............................

f) Li + F2 → ..............................

g) Mg + S → .............................

h) K + Cl2 → .............................

i) Mg + F2 → ............................

j) Li + O2 → ..............................

k) Na + O2 → .............................

l) Li + S → ................................




1. Find the formula Every compound has a specific formula. Elements in the same group of the periodic table form compounds with similar formulas.

Groups the elements are

from

Ratio of atoms in

compound

Typical formula

1 & 7 or 2 & 6 1 : 1 LiF or MgO 2 & 7 1 : 2 MgCl2 1 & 6 2 : 1 K2O

Write a formula for each of the following compounds:

a) calcium oxide _______________ g) magnesium sulfide _______________

b) calcium chloride _______________ h) potassium chloride _______________

c) sodium fluoride _______________ i) magnesium fluoride _______________

d) beryllium sulfide _______________ j) lithium oxide _______________

e) beryllium fluoride _______________ k) sodium oxide _______________

f) lithium fluoride _______________ l) lithium sulfide _______________

2. Line up the symbols … then balance the equation Equations can show how compounds form. To write an equation, first find every symbol and formula. The symbols for elements are in the periodic table. Many gases form molecules so their symbols have a subscript number. These symbols and formulas show what happens when magnesium burns:

The equation above is unbalanced because there are more oxygen atoms before the reaction than after. Two magnesium atoms need to react with each pair of oxygen atoms to form two ‘lots’ of magnesium oxide. So the balanced equation looks like this:

Write balanced equations to show elements reacting to form the compounds listed in part 1.



Mixtures: Worksheet 1.3.1

Successful separations Match each separation technique to the correct box in each column.

Separation technique Mixtures separated How it works Typical use

1 Filtration

A A liquid from the solid dissolved in it

F The solution becomes too concentrated for all the solid to remain dissolved

K To identify the dyes used to colour foods

2 Crystallisation

B Miscible liquids that dissolve in each other

G The liquid evaporates but the solid does not

L To obtain pure crystals of compounds used in medicine

3 Simple distillation

C Soluble substances

H An insoluble substance cannot pass through filter paper

M To obtain fresh water from seawater

4 Fractional distillation

D Insoluble solids from liquids

I One is more attracted to a solid, such as paper, so it doesn’t travel as far as the other

N To separate crude oil into different fuels, such as petrol and diesel

5 Chromatography

E A solid from the liquid it is dissolved in

J Liquids with higher boiling points stay in the flask until those with lower boiling points have evaporated

O To remove solids before waste water is purified



Mixtures: Worksheet 1.3.2

Which method? When a solution of sodium chloride reacts with a solution of silver nitrate, a new compound called silver chloride forms. This is insoluble so it forms a cloudy precipitate in the water.

1. Which separation method would you use to obtain a pure sample of the silver chloride?

Name the equipment you would need and explain how your method works.

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

2. Black ink can be made by mixing different combinations of coloured dyes. The dyes in ink can be compared to identify the pens used to write notes.

a) Which method would you use to separate the dyes in ink?

___________________________________________________________________________ b) Suggest one other use for this technique and explain how it works.

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________



3. Many chemical reactions take place in solution. The new compounds formed need to be separated from water.

How could you get crystals from a concentrated solution of copper sulfate? _______________ Explain how this method works.

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

4. Alcoholic drinks contain a mixture of ethanol (boiling point, 78 °C) and water (boiling point, 100 °C).

Spirits such as brandy contain a higher percentage of ethanol than wine and a lower percentage of water.

When wine is turned into brandy a lot of the water is left behind. Name the method used and explain how it works.

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________



Changing ideas about atoms: Worksheet 1.4.1

Developing the atomic model Cut out the cards. Find out when each scientist worked and arrange the cards in order. The thoughts of Democritus ‘I think everything is made of tiny spheres called atoms that can’t be broken down.’

Bohr’s calculations ‘I can improve Rutherford’s model. My calculations show that electrons only exist in certain energy levels. You can think of these as ‘shells’ around the nucleus.

Rutherford’s analysis ‘Geiger and Marsden’s results are shocking. The only explanation is that most of an atom is empty space. Nearly all its mass is in a tiny positive nucleus. The negative electrons must orbit around it.’

Thomson’s discoveries ‘Dalton’s ideas don’t explain my results. I proved that atoms contain tiny negative electrons. But atoms are neutral – so perhaps they are balls of positive charge with negative electrons stuck in – like plums in a plum pudding.’

Dalton’s evaluation of his experiments ‘My work with compounds suggests that Democritus was right about atoms.’

Geiger and Marsden’s scattering experiment ‘Our experiment was a bit stupid really. We made a piece of gold thinner than tissue paper and fired positive alpha particles at it. They should have gone straight through like bullets – but amazingly a few bounced back.’




Geiger and Marsden’s scattering experiment The evidence for Rutherford’s model of the atom came from some unexpected results obtained by Geiger and Marsden. They fired a beam of alpha particles through thin gold film. They expected the radiation to go straight through – like bullets through tissue paper – but some particles didn’t.

Rutherford was shocked. This could only happen if nearly all the mass of the gold particles was in a tiny positive sphere. This could only be true if most of the atom was empty space. Rutherford called the positive part of the atom the nucleus. He predicted that there must be neutral neutrons in the nucleus too. This theory became more convincing years later when another scientist, called Chadwick, found evidence that neutrons did exist.

1. Explain why most of the alpha particles went straight through the gold foil.

________________________________________________________________________ ________________________________________________________________________

2. What was sending some alpha particles off course or making them bounce off the foil?

______________________________________________________________________________

3. Explain why an atom like Thomson’s ‘plum-pudding’ model would not make alpha particles

change direction?

______________________________________________________________________________




Changing ideas These four scientists helped develop our model of the atom.

1. The diagrams show four models of a hydrogen atom. Write each scientist’s name under the model they are famous for.

2. Which scientist said: ‘Atoms are balls of positive charge with tiny electrons stuck in them.’

________________________________________________________________________

3. Which scientist thought atoms could never be broken down?

______________________________________________________________________________

4. Who said ‘Electrons occupy energy levels at different distances from the nucleus?’

______________________________________________________________________________

5. Which scientist’s model was refuted by Geiger and Marsden’s scattering experiment?

________________________________________________________________________

6. Which scientists’ models are supported by Geiger and Marsden’s results?

______________________________________________________________________________



Modelling the atom: Worksheet 1.5

Atoms We often use spheres or circles as model atoms, but real atoms are mostly empty space. All atoms have a similar structure. 1. Label the diagram below to show what atoms are like.

2. The diagram is not a very accurate model of a helium atom. List two differences between real atoms and the atom in the diagram.

___________________________________________________________________________

___________________________________________________________________________



Relating charges and masses: Worksheet 1.6

Inside atoms 1. Add ‘protons’, ‘neutrons’ and ‘electrons’

to the correct sections of the Venn diagram.

2. Explain what makes elements different from each other.

__________________________________________________________________________

3. Which components of an atom are involved when elements react to form compounds?

__________________________________________________________________________

4. Explain how to use the periodic table to state the number of electrons in any neutral atom.

__________________________________________________________________________

5. Complete the table:

Atomic number

Protons Electrons Charge

Li atom 3 3 3 0

Li ion 3 3 2 +1

Be atom

Be ion 2 +2

Na atom

Na ion 10

Mg atom

Mg ion 10

Al atom

Al ion 10



Sub-atomic particles: Worksheet 1.7.1

Neutrons

• The atomic number of an element is the number of protons in an atom.

• The mass number of an atom is the total number of protons and neutrons in an atom.

• So the number of neutrons = mass number − atomic number.

Complete the table to show how many neutrons each atom contains.

Atom Symbol Mass number

Atomic number Neutrons

Hydrogen 1

Helium 4

Lithium 7

Beryllium 9

Boron 11

Carbon 12

Nitrogen 14

Oxygen 16

Fluorine 19

Neon 20

Sodium 23

Magnesium 24

Aluminium 27

Silicon 28

Phosphorus 31

Sulfur 32

Chlorine 35

Argon 40

Potassium 39

Calcium 40



Sub-atomic particles: Worksheet 1.7.2

Neutrons

• The atomic number is the number of protons in an atom.

• The mass number of an atom is the total number of protons and neutrons in an atom.

• So the number of neutrons = mass number − atomic number The table shows the mass numbers of 20 different atoms.

1. Which of the atoms listed have more neutrons than protons?

___________________________________________________________________________

2. Do any of the atoms listed have fewer neutrons than protons?

___________________________________________________________________________

Isotopes The symbol for a specific isotope shows its mass number and atomic number: This can be described simply as ‘aluminium-27’.

1. Write symbols for sulfur-32, chlorine-35, argon-40, potassium-39 and calcium-40.

___________________________________________________________________________

2. List the number of sub-atomic particles in atoms of carbon-12, carbon-13 and carbon-14.

___________________________________________________________________________

Atom Mass number Atom Mass

number Atom Mass number Atom Mass

number

hydrogen 1 carbon 12 sodium 23 sulfur 32

helium 4 nitrogen 14 magnesium 24 chlorine 35

lithium 7 oxygen 16 aluminium 27 argon 40

beryllium 9 fluorine 19 silicon 28 potassium 39

boron 11 neon 20 phosphorus 31 calcium 40



Electronic structure: Worksheet 1.8.1

Electron configurations The shells closest to the centre (lowest electron energy levels) are filled first. The first shell can hold two electrons. The next three shells can hold eight electrons. .




Electronic structure diagrams

Complete the grid by drawing diagrams to show the electronic structure of atoms with the following numbers of electrons.

1 electron

2 electrons 3 electrons

4 electrons


7 electrons


10 electrons

11 electrons

16 electrons

18 electrons





Electronic structure by numbers 1. Use number notation to show the electronic structure of these elements:

a) an atom with 12 electrons b) an atom with 13 electrons c) an atom with 1 electron d) an atom with 20 electrons e) an atom with 7 electrons f) an element with atomic number 6 g) an element with atomic number 17 h) an atom with 17 protons i) an atom with 3 protons j) an element with a mass number of 23 and atomic number 11.

2. A quick check that your answers to question 1 are correct is that;

the sum of all the numbers = the number of electrons in an atom Or the atomic number. So, for an atom with 14 electrons and an electronic configuration of 2,8,4, 14 = 2 + 8 + 4, which is correct. Check your answers to question 1.

3. Use numbers to write the electronic structure of:



The periodic table: Worksheet 1.9.1 Electronic arrangements The table shows the electron shells used by elements with atomic numbers from 1 to 20. Turn the page sideways and add each element’s symbol. Fill in each atom’s electrons and write out their electronic structures.



The periodic table: Worksheet 1.9.2

Outer electrons and groups 1. a) Complete the table.

Group number Number of electrons in outer shell

Example of element and its electronic structure

1

2

3

4

5

6

7

0

b) Write a sentence describing the relationship between the group number and the number of

electrons in the outer shell.

_________________________________________________________________________

2. Students have been researching some properties of some elements. The table shows their results (the states are as at room temperature).

Element Properties

Argon Very unreactive gas.

Lithium Reactive grey metal, stored under oil, reacts with water to give off hydrogen gas.

Fluorine Pale yellow gas, very reactive, reacts with metals to produce fluorides.

Sodium Very reactive grey metal, stored under oil, reacts violently with water to give off hydrogen gas.

Caesium Extremely reactive grey metal, stored under oil, explodes with water, producing hydrogen gas

Neon Very unreactive gas

Helium Very unreactive gas.

Potassium Very reactive grey metal, stored under oil, reacts violently with water to give off hydrogen gas.

Chlorine Yellow gas, very reactive, reacts with metals to produce chlorides.

Bromine Red/brown liquid, extremely reactive, reacts with metals to produce bromides.

Decide which elements are in the same group and whether or not these observations support the idea that elements with the same number of electrons in their outer shell has similar properties.

Groups: _____________________________________________________________________

___________________________________________________________________________



The periodic table: Worksheet 1.9.3

Atoms and electrons

Group the cards for each element. Then describe the connections between their positions in the periodic table and the way their electrons are arranged.

Lithium a Group 1

metal

2,8,2

2,8,7 Magnesium a Group 2

metal

2,6 Chlorine

a Group 7 non-metal

2,8 Neon

a Group 8 non-metal

2,1

Oxygen a Group 6 non-metal

Documents

Elements and compounds: Worksheet 1.1 · For example, a compound made from magnesium and oxygen is called magnesium oxide. The name of the metal part does not change, but oxygen is