7.1 general structure of the periodic table. - webs 4 chem chapter 1.pdf · chemistry – form 4...

Chemistry – Form 4 Ms. R. Buttigieg

7.1 General structure of the Periodic Table.

What you should know already Complete the passage using words from the list. You can use words more than once acidic alkaline calcium carbon dioxide chlorine copper hydrogen lead left magnesium magnesium oxide metals neutral neutralization nitrogen oxygen periodic table reactivity series right sodium hydroxide symbol zinc sulphate universal indicator 1. Each element can be represented by one or two letters called a _______________.

2. Which element is represented by each of the following:

Ca ____________ O ____________ Mg ____________

Cl ____________ Pb ____________ N ____________

3. Elements are shown in the _________________________.

4. Most of the known metals are ______________.

5. Metals are on the ____________ hand side and non-metals are on the ____________

hand side of the periodic table.

Complete the following word equations:

6. Magnesium + Oxygen � ____________

7. Sodium + Water � ____________ + ____________

8. Zinc + Sulphuric Acid � ____________ + ____________

9. Magnesium + Copper (II) oxide � ____________ + ____________

10. Metals are arranged in order of reactivity in the ____________

Complete:

11. The pH of a solution can be found using a pH meter or _________________________.

12. A solution with a pH of 7 is ____________. Solutions with a pH less than 7 is

____________ and greater than 7 is ____________.

13. Reactions between acids and alkalis are __________________ reactions.


See Books - Chemistry for You Chapters 4, 5, 6

GCSE Chemistry Chapter 3 pgs 39-50

7.1.1 The table as a series of vertical Groups and horizontal periods. Rows of the Periodic table are called Periods Columns of the Periodic table are called Groups

Read Chemistry For You pg. 43

What is interesting however is that: - The number of electrons in the outer shell gives us the Group Number So all the elements, whose atoms have the same number of electrons in their outer shell, are grouped together.

- The number of electron shells gives us the Period Number.

a. In the modern periodic table, what are the elements arranged in order of?

_____ their first letter _____ atomic number _____ relative atomic mass

b. What are the vertical columns called?

_____ periods _____ trends _____ groups


7.1.2 The areas of the table, which contain reactive metals, transition metals, characteristic non-metals, and the noble gases.

You should be able to identify these areas on an outline of the periodic table.

I suggest you learn them well ok!!!

See the periodic table on GCSE Chemistry pg. 40

See the periodic table on Chemistry for You pg. 43 and pg. 392

Work out Chemistry For You pg. 49 numbers 1, 5.

pg. 73 number 1

7.1.3 The noble gases as an unreactive group. Group 8 is also called Group 0 or the Noble Gas group. All the elements in this group have a full outer shell. So, they have no “desire” to lose or gain electrons so they are very stable and are very unreactive as a group.

Until about 40 years ago it was believed that they never reacted. We now know that they form some compounds, e.g. xenon tetrafluoride, XeF4

Some uses of the Noble gases (Revision Form 3) – rely on their unreactivity

Noble Gas Use Helium Balloons and airships – less dense than air Neon Filling advertising tubes Argon Filling electric light bulbs, inert atmosphere

for welding Krypton and xenon Lighthouse and projector bulbs. Lasers Radon Killing cancerous tumours


7.1.4 Relating the Group number / electron configuration to metallic / non- metallic character.

Elements of group 1, 2, 3 that give away 1, 2 and 3 electrons respectively are the metals.

Elements of groups 6, 7 that accept 2 and 1 electrons respectively are the non-metals.

7.1.5 The metalloids (e. g. silicon and germanium). Read Chemistry for You pg. 48 The metalloids are not as good a set of conductors as the metals, but they are better conductors than the nonmetals. Many of them are known as semiconductors. Also, unlike the metals, which become better conductors at low temperatures, the metalloids become better conductors at higher temperatures. Because of their unique electrical conductivity, the metalloids have drawn a lot of attention from the computer and electronics industries. When involved in chemical bonding, the metalloids again exhibit middle-of-the-road qualities. They are capable of taking electrons from most metals and will readily lose electrons to most nonmetals. Their electronegativity values are also mid-range. So it is unlikely for them to be involved in ionic bonding. They will usually establish covalent bonding when found in compounds.


Here is a list of elements. Use your periodic table to answer these questions.

Chlorine, helium, lithium, magnesium, titanium

1. Which element is in period 1? _________________

2. Which element is in group 2? _________________

3. Which element is an alkali metal? _________________

4. Which element is a halogen? _________________

5. Which element is a transition metal? _________________

6. Which element is a noble gas? _________________

7. Which elements have atoms containing 2 electrons in the outer energy levels?

_________________, _________________

8. Which two of these elements are in the same period of the periodic table?

_________________, _________________

7.2 Trends in properties across a period (Na to Ar)

Group 1 2 3 4 5 6 7 8 Element Na Mg Al Si P S Cl Ar

Character Metallic Metalloid Non-metallic Noble Gas

Reactivity ----Decreases-----> - <----Decreases---- - Structure of

element Giant metallic Giant

covalent Molecular Atomic

Ion Na+ Mg2+ Al3+ None P3- S2- Cl- None Oxide Na2O MgO Al2O3 SiO2 P2O5

P2O3

SO2

SO3

Cl2O None

Type of oxide

Strongly basic amphoteric Acidic None

Structure of oxide

Giant ionic Giant covalent

Molecular None

o Change from metallic to non-metallic character across a period

� From left to right across a period, there is a transition from metals to non-metals.

o Note the change in reactivity o Note the type of ions formed. (valency) o Note the type of bonding –

� From left to right across a period the bonding in chlorides or oxides changes from ionic (with metals e.g. Na+Cl-) to covalent (with non-metals e.g. SO2).

o Note the compounds they form � From left to right across a period the oxides change from alkaline/basic (with

metals e.g. Na2O) to acidic (with non-metals e.g. SO2). � Note the change from basic, through amphoteric to acidic nature.


1 2 3 4 5 6 7 8 As you can note after drawing the missing electrons, the number of electrons increases as you move to the right of the period. (In reality note that the radius of the atom becomes a bit smaller) This is what causes the change in the properties of the elements as you move across a period.

7.3 Trends down typical metallic groups Group 1 Metals Group 1 elements all have one electron in the outer shell or energy level.

Group 1 contains very reactive metals including lithium, sodium and potassium. They are so reactive that they have to be stored in oil to prevent them from reacting with the air.

If a new group 1 element was discovered which 2 of these properties would it have?

� It would be a metal with high melting and boiling point. � It would be a metal with low melting and boiling point. � It would be a gas with low melting and boiling point. � It would react with water to form an alkaline solution. � It would react with water to form an acidic solution and hydrogen.

How the number of electrons changes across a period GROUP NUMBER

These are not typical metals

because they tend to be soft and light. They also have low melting and boiling

points.


Lets take sodium as an example. A sodium atom has 11 protons in the nucleus surrounded by 11 electrons.

The smaller an atom, the closer its outer electron is to the nucleus, and the more difficult it is to remove. This is because there is a strong attractive force on it from the positive protons in the nucleus.

As you go down the group, the size of the atoms increases and the outer electron gets further away from the nucleus and therefore becomes easier to remove.

This means that as you go down the group, the reactivity increases.

This trend shows that as you go down Group 1, the elements become more reactive. Remember, all Group 1 elements have just one electron in their outer energy level. When they react they lose this electron. By doing this, they obtain a full outer energy level. They become more stable because they now have the electron structure of a noble gas.

When the sodium atom reacts and becomes a sodium ion, it loses one electron. There are now 11 protons in the nucleus surrounded by 10 electrons, so the overall charge on the ion will be 1+. The sodium ion is written as Na+. Na+ is a positive ion. The outer shell is full, so the ion is stable.


Electronegativity is the measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond.

Occurrence and Extraction

These elements are too reactive to be found free in nature. Sodium occurs mainly as NaCI (salt) in sea-water and dried-up sea beds. Potassium is more widely distributed in minerals such as sylvite, KCI, but is also extracted from sea-water. The alkali metals are so reactive they cannot be displaced by another element, so are isolated by electrolysis of their molten salts.

Burn vigorously in air to form the oxide: The oxides formed are white. Flame colours are different.

Li red Na yellow K lilac Rb red Cs blue

a) Lithium (s) + Oxygen (g) � Lithium oxide (s)

_______________________________________

b) The alkali metal oxides then dissolve in water to form alkali solutions

Li 2O (s) + H2O (l) � 2 LiOH (aq)

_______________________________________

Reaction with water: These are strongly alkaline solutions and because of this these elements are also called the alkali metals. Lithium reacts smoothly with cold water. It moves about on the surface of the water. A solution of Lithium hydroxide is formed and hydrogen gas is given off. Lithium (s) + Water (l) �� Lithium hydroxide (aq) + hydrogen (g) Sodium reacts vigorously with cold water. It moves about on the surface of the water & melts into a silvery ball. A solution of Sodium hydroxide is formed and hydrogen gas is given off.

Potassium reacts violently

with cold water. It moves

about on the surface of the

water & melts into a silvery

ball, then catches fire. It burns

with a lilac flame.


Group 2 Metals Group 2 elements all have one electron in the outer shell or energy level.

� Harder then Group 1 � Silvery-grey � Good conductors � Burn in air to form the oxides. � Less reactive than their neighbor Group 1 Metals

In group 2 we find magnesium and calcium. Both are metals. But calcium is more reactive than magnesium. (as it has more shells). � Calcium reacts steadily with cold water. It falls to the bottom, giving off hydrogen and forming

calcium hydroxide. Calcium hydroxide is slightly soluble in water. So the solution becomes cloudy due to the formation of undissolved calcium hydroxide.

Calcium (s) + Water (l) � Calcium hydroxide (aq) + Hydrogen (g)

_________________________________________________________________________________

Calcium reacts vigorously with acids. Calcium (s) + Hydrochloric acid (aq) � Calcium Chloride (aq) + Hydrogen (g)

________________________________________________________________________

� Magnesium reacts slowly with water, fast with steam and fast with acids. A piece of clean magnesium ribbon is placed in water and a test tube full of water is inverted over it. It takes several days to collect some hydrogen gas in the test tube. Magnesium (s) + Water (l) � Magnesium hydroxide (aq) + Hydrogen (g)

________________________________________________________________________

Magnesium reacts vigorously with steam. Steam is passed over the heated magnesium. The Magnesium reacts by glowing white and forms white magnesium oxide powder. Hydrogen is formed which can be lighted at the opening of the glass tubing. Magnesium (s) + Steam (l) � Magnesium hydroxide (aq) + Hydrogen (g)

________________________________________________________________________

Strontium & Barium also react well with water. ___________________ is the more reactive of the two. See GCSE Chemistry pg. 44, Chemistry for You pg. 54-55 Work out Chemistry for You: Pg. 60 number 3 (You need a graph paper) Pg. 74 number11, 13, 15b,17.


A. Underline the correct word/s: 1. Metals are electropositive/electronegative. 2. Non-metals are electropositive/electronegative. 3. Metals react by giving/receiving/sharing electrons. 4. Non-metals react by giving/receiving/sharing electrons. 5. Down a group electronegativity increases/decreases. 6. Across a period electronegativity increases/decreases. 7. Non-metals are found on the right/left hand side of the table.

8. Group 1 are called the _______________________.



11. The shallow block in the table are the _______________________.

12. Group 8/0 are called the _________________________.

B. Complete the table below: (the first one has been done for you)

Group 1 2 3 4 5 6 7 8 Element Na Mg Al Si P S Cl Ar

Character metal

Electron configuration

2, 8, 1

Valency

1

Ion Na+

Oxide Na2O

Type of oxide basic

Structure of oxide

Giant ionic

C. Write the chemical equations for the given word equations: (don’t forget state symbols) Sodium + Water �� sodium hydroxide + hydrogen

_____________________________________________________

Magnesium + Oxygen �� Magnesium Oxide

_____________________________________________________

Calcium + Hydrochloric Acid �� Calcium Chloride + Hydrogen

__________________________________________________________


JUNIOR LYCEUM ANNUAL 2002

Elements in the same Group of the Periodic Table show a similarity in physical and chemical

properties. The elements also show a trend in reactivity.

Barium is in Group 2 of the Periodic Table. Use your knowledge of the Group 2 metals (e.g.

Mg, Ca) to answer the following questions about Barium.

(a) (i) What is the number of electrons in the outer shell of a barium atom? ____

(ii) Write down the formula for the barium ion. ______ (2 marks)

(b) Predict one physical property that you would expect barium to show.

_________________________________________________________ (1 mark)

(c) How would you expect barium to be extracted from its compounds?

_________________________________________________________ (1 mark)

(d) (i) State one thing you would expect to see when barium is added either to water, or to dilute

hydrochloric acid.

_____________________________________________________ (1 mark)

(ii) Give a balanced equation for the reaction of barium - with water,

____________________________________________

with dilute hydrochloric acid. ____________________________________________ (4 marks)

(e) Would you expect barium to be more, or less reactive, than magnesium and calcium?

_________________________________________________ (1 mark)

2. (a) (i) What are allotropes? ______________________________________________________________________________

___________________________________________________ (2 marks)

(ii) Name the two allotropes of carbon.

___________________________________________________ (2 marks)

3. Consider the following ‘pairs of elements’:

sodium and potassium ; magnesium and calcium

(a) For EACH pair; give two typical PHYSICAL properties which are similar for both elements.

(4 marks)

(b) For EACH pair describe fully a reaction, including the observations and equations, which

show that both elements have similar CHEMICAL properties.

(8 marks)


7.4 The Transition Metals

Read Chemistry For You: Transition Elements pg. 56, 57 v.important Extraction of Iron (Blast furnace) pg. 91-93

make sure you know all the equations for the blast furnace reactions

The transition metals are found in the large block between Groups 2 and 3 in the periodic table

Common properties of the TRANSITION ELEMENTS:

1. They are metals 2. They are hard and strong 3. Have high melting points (except mercury) and densities 4. Have variable valency (charge on ion) e.g. Iron (II) and Iron (III) – valency 2 or 3. 5. Form coloured compounds

� These include blue copper(II) sulphate and orange-brown rust (a type of iron oxide).

6. Many of them have catalytic activity � Catalysts make reactions go faster without being used up during the reaction.

Transition metals such as platinum and rhodium are found in catalytic converters.

7. Good conductors of heat and electricity 8. Can be hammered or bent into shape easily 9. Less reactive than alkali metals like sodium

Some examples:

Work out : Chemistry for You page 60 number 1; page 61 number 8 Page 99 number 5. (see pg. 91 to help you answer).


1. Iron is extracted in a Blast Furnace

(a) (i) Name two raw materials that go into a Blast Furnace.

______________________________________________________________

(ii) Name two substances, (apart from iron), that come out of a Blast furnace.

_______________________________________________________(4 marks)

(b) Most of the iron leaving the furnace is converted into steel.

(i) Give one reason why pig iron is not as useful as steel.

______________________________________________________________

(ii) Give one use of steel and state the property upon which this use depends

______________________________________________________________

_______________________________________________________(3 marks)

2. Give the letter of the area in which you would find – (Junior Annual 2001)

A) Give the letter of the area in which you would find – i) elements that do not tend to form compounds _______ ii) the most reactive metals _______ iii) a metal which is borderline with non-metals and whose oxide is amphoteric _______ iv) a solid non-metal that burns in air to form an acidic oxide _______ v) a metal that has a variable valency and forms coloured ions _______ vi) a halogen _______ vii) an element that reacts with water to form an alkaline solution _______ B) Give the number of electrons in the outer shell of the atoms of i) most noble gases ________ ii) metals that form ions of the type X2+

________ iii) non-metals that form ions of the type X -

________ (10 marks)


How does the blast furnace work?

The Blast Furnace is a large steel structure about 30 metres high. It is lined with refractory firebricks that can withstand temperatures approaching 2000oC. The furnace gets its name from the method that is used to heat it. Pre-heated air at about 1000oC is blasted into the furnace through nozzles near its base. The largest Blast Furnaces in the UK produce around 60 000 tonnes of iron per week. The largest on in Europe, has produced up to 11 000 tonnes per day (77 000 tonnes per week) but is currently running at 8000 tonnes per day. This is equivalent to all the iron needed for about 5 cars every minute.

Refining iron

The metal that leaves the Blast Furnace contains between 4% and 5% of carbon. This much carbon makes a very hard but brittle metal which is not much use. The next step in the production of steel is to reduce the levels of carbon and other impurity elements in the hot metal.


Make sure you know: The principle of extraction from haematite in the Blast furnace, including function of limestone

in removing main impurity. - uses of pig iron and steel related to the

difference in their physical properties. - Revise rusting and its prevention (it’s the

opposite of what happens in the blast furnace)

� Pig iron is an alloy containing about 3% carbon with

varying amounts of S, Si, Mn, and P. It is hard,

brittle, fairly fusible, and is used to produce other

alloys, including steel.

� Steel is a mixture of iron and carbon. The amount of carbon may range from 0·1% to 1·5% giving steels of

different properties. Steel is used to make

machinery, tools, cars, large girders and bridges.

Oxidation – Oxidation Is Loss of electrons Reduction – Reduction Is Gain of electrons OIL RIG (see Chem 4 U pg. 115)

Iron and Copper - both are transition metals. Iron (II) compounds are green. Copper (I) compounds are red Iron (III) compounds are brown. Copper (II) compounds are blue.

Iron exhibits a valency of 2 and 3

e.g. Iron(II)sulphate FeSO4 and iron(III)sulphate Fe2(SO4)3

Copper exhibits a valency of 1 and 2

e.g. Copper (I) chloride CuCl and Copper(II)chloride CuCl2

And copper(I)sulphate Cu2SO4 and copper(II)sulphate CuSO4. To make Iron (II) chloride, iron is reacted with hydrochloric acid or hydrogen chloride is passed over heated iron. Fe (s) + 2HCl (aq) � FeCl2 (aq) + H2 (g) Fe (s) + 2HCl (g) � FeCl2 (s) + H2 (g) To make Iron (III) chloride, iron is reacted with chlorine. The Iron is heated to start the reaction: 2Fe (s) + 3Cl2 � 2FeCl3 (s) When you convert and iron(II) compound into an iron (III) compound, you are oxidizing iron (II) into Iron (III).

Fe++ - e- � Fe+++ oxidising is loosing electrons


To convert an iron(III) compound into and iron (II) compound, a reducing agent is needed.

Fe+++ + e- � Fe++ Reduction is gaining electrons

You can use oxidising agents like sulphur dioxide and hydrogen sulphide. When you bubble sulphur dioxide through iron (II) compound solution, the brown solution turns to pale green.

Copper will react with oxygen in the air to form copper(II) oxide.

copper + oxygen copper(II) oxide. 2Cu(s) + O2(g) 2CuO(s)

Reaction of copper with acids

Copper metal dissolves in hot concentrated sulphuric acid to form solutions containing the aquated Cu(II) ion together with hydrogen gas, H2.

Cu(s) + H2SO4(aq) Cu2+(aq) + SO42-(aq) + H2(g)

Copper metal also dissolves in dilute or concentrated nitric acid, HNO3

Triiron tetraoxide and hydrogen are formed when iron reacts with steam.

(a) Label the diagram below, which shows a set up suitable for carrying out the

reaction in the laboratory.

Complete the diagram to show how a test-tube of the hydrogen given off can be

collected. (5 marks)

(b) The unbalanced equation for the reaction of iron with steam is shown below:

Balance the equation

Fe + H2O → Fe3O4 + H2

(c) Cobalt is a transition metal. State two properties you would expect cobalt to have,

which are typical of a transition metal.

________________________________________________________________________


7.5 The Halogens – Group 7

Read Chemistry For You: Group 7 – the halogens pg. 62- 65 GCSE Chemistry: Group 7 – the Halogens pg. 45 - 48

Fluorine and chlorine are poisonous gases, bromine is a brown, fuming liquid and iodine an almost-black solid with a poisonous purple vapour.


All the halogens:

� Are coloured and become darker as you go down the group

� Are found as molecules and form molecular (covalent) compounds with other non metals like hydrogen e.g HCl. With Hydrogen the hydrogen halides are formed, they dissolve in water to form acidic solutions (pH < 7) e.g. H2 (g) + Cl2 (g) � 2HCl (aq)

� The molecules are diatomic (2-atom) molecules, namely Br2, F2, Cl2, I2,

Reactions with water: Chlorine reacts with water to form 2 acids – hydrochloric acid and hypochlorous acid (bleach)

Cl2 (g) + H2O (l) � HCl (aq) + HOCl (aq)

Bromine is less acidic than chlorine. Iodine is weaker still. (almost insoluble in water but made soluble in the presence of potassium iodide solution KI)

Reactions with Group I and II metals: The others react in more or less the same way.


Reactions with Iron When iron wool is heated with chlorine, the iron glows brightly, and reacts vigorously to produce a brown smoke. Brown iron chloride is left behind.

2Fe (s) + 3Cl2 (g) � 2FeCl3

When iron is heated with Iodine the iron glows even less brightly than with bromine, but brown smoke and brown iron iodide are left behind. Bleaching effect on water containing an indicator; � Chlorine bleaches damp litmus and is very reactive. Chlorine reacts with water, forming

hypochlorous acid. Cl2 (g) + H2O (l) � HOCl (aq) + HCl (aq)

Hypochlorous acid is a very reactive compound that readily give sup its oxygen to the dye, to form a colourless compound.

HOCl (aq) + dye or indicator � HCl + (dye + O colourless) The product must then be thoroughly washed to remove HCl or it will be attacked by the free acid.

o Bromine is also a bleaching agent but not as rapid as chlorine. o Iodine does not bleach.

Displacement Reactions – If chlorine is bubbled into a solution of potassium bromide, then the less reactive halogen, bromine, is displaced by the more reactive halogen, chlorine.

2KBr (aq) + Cl2 (g) � 2KCl (aq) + Br2 (aq)

� Chlorine gives salts called chlorides.

� Bromine gives salts called bromides.

� Work out GCSE Chemistry pg. 48 numbers 1 and 2


Iron can form two chlorides.

(a) When dilute hydrochloric acid is reacted with iron, a pale green iron chloride solution is

formed. Hydrogen is also liberated.

(i) What is the valency of iron in this chloride? _________________ (1 mark)

(ii) Write a balanced equation for this reaction.

_____________________________________________________ (2 marks)

(b) When sodium hydroxide is added to a solution of the green iron chloride, a green precipitate

is formed. This precipitate goes darker on standing.

(i) Give an equation to show the formation of the green precipitate.

_____________________________________________________ (2 marks)

(ii) Why does the precipitate darken on standing?

_____________________________________________________ (1 mark)

(c) When chlorine is passed over heated iron, a brown iron chloride is formed.

(i) What is the valency of iron in this chloride? __________________ (1 mark)

(ii) Give a reason why chlorine gives this brown chloride with iron, not the same chloride formed

with dilute hydrochloric acid.

______________________________________________________________________________

______________________________________________________________________ (1 mark)

(d) Iron is a transition metal. Write down two properties which are typical of a transition metal,

and that are illustrated in the above reactions.

_________________________________________________________________

_________________________________________________________ (2 marks)

(e). Consider the following list of metals.

Zn, Mg, Cu, Ag, Fe, Al.

Rewrite this list of metals, starting with the most reactive.

____________________________________________________ (2 marks)

7.1 general structure of the periodic table. - webs 4 chem chapter 1.pdf · chemistry – form 4...

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