CHEMISTRY Form 4 CHAPTER 4-The Periodic Table

7/29/2019 CHEMISTRY Form 4 CHAPTER 4-The Periodic Table

1/47

Chapter: 4

The Periodic Table of

Elements

4.1 The Periodic Table of Elements

Historical Development of the Periodic Table

** Arrangement of elements in the Periodic Tablea) Elements are arranged in an _______________________________________

b) Vertical columns are called group _______________________________

c) Horizontal rows are called period _________________________________________

d) Elements with __________________________________ are placed in the ___________

e) The ________________________ of the elements with __________________________

= the _______________ of valence electrons in its atom.

f) The group number of the elements with ______________________ valence electrons

= the number of valence electrons in its atom + 10

g) The ________________ number of an element = the number of ___________________________

_____________________________ in its atom.

Complete the table below

Element H11

He4

2Li7

3 Be9

4B

11

5C12

6N14

7O16

8F19

9Ne20

10

Electron arrangement 2.

1

2.

4

2.

7Number of valence

electrons2 8

Group 14 17Number of shells occupied 2Period 2Element Na

23

11Mg

24

12Al27

13 Si28

14P31

15S32

16Cl5.35

17Ar40

18K39

19Ca

40

20

Electron arrangement 2.8.

1Number of valence

electrons6

Group 1 16 2

1 | P a g e


2/47

Number of shells occupied

Period 3 4

2 | P a g e


3/47

3 | P a g e


4/47

4 | P a g e


5/47

5 | P a g e


6/47

An atom of element E has 10 neutrons. The nucleon number of element E is 19. In

which group and period is element E located in the Periodic Table?

An atom of element G has 3 shells occupied with electrons. It is placed in group

17 of the Periodic Table. What is the electron arrangement of atom G?

4.2 Group 18 Element known as noble gases: Helium, neon, argon, krypton, xenon & radon

monoatomic

all noble gases are inert chemicallt unreactive

** The electron arrangement of noble gases are very stable because the

outermost occupied shells are full

Uses of Group 18 elements:

1. Helium gas to fill airships and weather balloons

2. Neon gas used in advertising lights and television tubes

3. Argon gas to fill light bulbs

4. Krypton gas used in lasers to repair the retina of the eye

5. Radon gas treatment of cancer

6. Xenon gas used for making electron tubes and stroboscopic lamps

6 | P a g e

Helium has duplet electron arrangement. Other noble

gases have octet electron arrangement


7/47

7 | P a g e


8/47

8 | P a g e


9/47

4.3 Group 1 Elements (Alkali Metals)

Lithium, sodium, potassium, rubidium, caesium & francium

uses of Group 1 elements:

a) Lithium batteries in calculator, watches and cameras

b) Sodium - 32CONa in soda-lime glass

c) Potassium - 3KNO as fertiliser.

* physical properties: softmetals, low densities, low melting & boiling points,silvery and shiny surfaces, good conductors of heat and electricity

9 | P a g e


10/47

When going down the Group 1, the melting point and boiling point decrease:

melting & Li

boiling points Na

decrease K

Explain why.__________________________________________________________________

__________________________________________________________________

10 | P a g e


11/47

Chemical Properties of Group 1 Elements

1. react vigorously with water to produce alkaline metal hyrdroxide solutions and hydrogen gas

Example: Li2 + OH22 LiOH2 + 2H

Write down the balanced equation when potassium reacts with water

_______________________________________________________________

2. react (burn) in oxygen gas rapidly to produce white solid metal oxides

Example: Li4 + 2O OLi22

Write down the balanced equation when rubidium reacts with oxygen

_______________________________________________________________

3. burn in chlorine gas 2Cl , to form white solid metal chlorides.

Example: Na2 + 2Cl NaCl2

Write down the balanced equation when potassium reacts with chlorine gas

_______________________________________________________________

** The reactivity of Group 1 elements increases when going down the group.

Explain why.

______________________________________________________________________________________________________________________________

_______________________________________________________________

** Potassium reacts more vigorously with water as compared to sodium. Explain.

(Proton number: Na, 11 ; K, 19)

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

* Safety Precaustion In Handling Group 1 Elements

1. All alkali metals must be ____________________________________ in bottles.

2. Use ____________ to take the alkali metals

3. Wear _________________ and ___________.

4. A ______________ piece of alkali metal is

used when conducting experiments.

To Investigate The Chemical Properties of Lithium, Sidum & Potassium

(A)The Reaction of alkali metals With Water, OH2

Problem Statement: How does the reactivity of Group 1 elements change when

they react with water?

Hypothesis: When going down Group 1, alkali metals become more

reactive in their reactions with water.

Variables: Manipulated variable Different types of alkali metals

Responding variable Reactivity of metals

Fixed variables water, size of metals

11 | P a g e

To prevent the alkali react

with ___________!

Lithium hydroxide

Lithiumoxide


12/47

Procedure:

1. Cut a ___________________ of lithium using a knife and forceps.

2. __________ the ____________ on the surface of the lithium with filter paper.

3. Place the lithium slowly _________________________ in a trough using a forceps.

4. When the reaction stops, test the solution produced with _____________________.

5. _______________ steps 1 to 4 using sodium and potassium to replace lithium one by one

6. ______________________ your observations.

Data & Observation

Alkali metal Observation

Lithium

Sodium

Potassium

(B) The Reaction of alkali metals With Water, OH2

Problem Statement: _________________________________________________

_________________________________________________

Hypothesis: ______________________________________________________________________________________________________

Variables: Manipulated variable ________________________________

Responding variable ________________________________

Fixed variables ____________________________________

Procedure:

1. Cut a small piece of lithium using a knife and forceps.

2. Dry the oil on the surface of the lithium with filter paper.

3. Put the lithium in a ____________________ and ______________________ until it _________.

4. Transfer the gas jar spoon quickly into a gas jar filled with _______________ gas

5. Observe what happens.

6. When the reaction stops, pour 10cm3 of _________ into the gas jar. Shake the gas jar. Test the

solution formed with ___________________________________________

7. Repeat steps 1 to 6 using _________________________________ to replace lithium one by one

8. __________________ your observations.

Data & Observation


LithiumSodium

Potassium

12 | P a g e

This procedure also can be

used to test the reaction ofalkali metals with chlorine

gas!


13/47

Based on your results, arrange the alkali metals in ascending order of reactivity.

_______________________________________________________________

Write the chemical equations for the reactions between the products from the

combustion of each alkali metal with water.

1. ____________________________________________________________

2. ____________________________________________________________

3. ____________________________________________________________

Name the substance formed when caesium reacts with chlorine gas. Write the chemical equation

for this reaction.

_______________________________________________________________

4.4 Group 17 Elements (Halogens)

Fluorine, chlorine, bromine, iodine and astatine


1) Chlorine water treatment, bleaching agent

2) Bromine weaker bleaching agent

3) Iodine needed in human thyroid gland to produce hormones

*Physical properties: __________ melting and boiling points.

Fluorine: pale yellow gasChlorine: greenish-yellow gas

Bromine: reddish-brown gas

Iodine: purplish-black gas

*Remember

2Cl melting and colour of Density

2Br boiling points halogens increases

2I increase becomes

darker

13 | P a g e


14/47

14 | P a g e


15/47

15 | P a g e


16/47

When going down the Group 17, the melting and boiling points increase. Explain

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

** Chemical Properties of Group 17 Elements

1. react with water to form two acids

Example: 2Cl + OH2 HCl + HOCl

hydrochloric hypochlorus

acid acid

Write a balanced equation when bromine reacts with water.

__________________________________________________________________

2. In gaseous state react with hot iron to form a brown solid, iron (III) halides.

Example: Fe2 + 23Br 32FeBr

Write a balanced equation when iodine vapour reacts with iron

__________________________________________________________________

3. react with sodium hydroxide solution, NaOH, to form sodium halide, sodium halite (I) and

water

Example: 2I + NaOH2 NaI + NaOH + OH2

Write a balanced equation when chlorine reacts with sodium hydroxide solution

__________________________________________________________________

The reactivity of Group 17 elements decreases when going down the group. Explain why.

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________

Chlorine gas reacts more vigorously with hot iron as compared to bromine gas. Explain (Proton

number: Cl, 17 ; Br, 35)

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________

16 | P a g e

Rememberduring the

reactions to form

halides, all halogens are

decolourised

F2is a very

dangerously

reactive

substance!

Do you know why F2

is not used in school

laboratories?

Cl2

gas, Br2

gas and I2

vapour are poisonous!

We must handle them ina fume chamber!


17/47

To investigate the Chemical properties of Group 17 elements.

The Reaction of halogens with iron


they react with iron?

Hypothesis: When going down Group 17, the halogens become less reactive in

their reactions with iron.

Variables: Manipulated variable Types of halogens

Responding variable Reactivity of halogens

Fixed variable iron

Procedure:

1. Heat the _______________ in the combustion tube ________________2. When the iron wool becomes ______________, pass the chlorine gas over the hot iron wool.

3. Observe any changes and record your observation.

4. Repeat steps 1 to 3 using ________ vapour and ______ vapour to replace chlorine gas one by one.

Data and Observation

Halogens Observation

Chlorine

Bromine

Iodine

What is the function of soda lime in this experiment?

__________________________________________________________________

Why must the iron wool be heated first before the halogens are passed over it?

__________________________________________________________________

Name the products for the reactions between chlorine, bromine and iodine with iron. Write the

chemical equations for these reactions

1. Name:_______________________ Equation:___________________________

2. Name:_______________________ Equation:___________________________

3. Name:_______________________ Equation:___________________________

Based on your results, arrange the halogens, 2Cl , 2Br , 2I in ascending order of reactivity.

__________________________________________________________________

17 | P a g e


18/47

Element E is placed below element D in Group 17 of the Periodic Table.

(a). Compare the melting and boiling points of element D with element E. Explain

your answer

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

(b). Write an equation for the reaction between element D and hot iron

_______________________________________________________________

4.5 Elements In A Period

Example: Period 3 in the Periodic Table Properties of Elements

Element Na Mg Al Si P S Cl Ar

Proton number 11 12 13 14 15 16 17 18

Electron

arrangement

Atomic radius

(pm)

186 160 143 118 110 104 100 94

Physical state at

room

temperature

Solid Solid Solid Solid Solid Solid Gas Gas

Electronegativity 0.9 1.2 1.5 1.8 2.1 2.5 3.0 -

* Across Period 3:

1. The proton number ________________ by one unit from one element to the nextelement

2. All the atoms of elements have _______________ shells occupied with electrons.

3. The number of valence electrons in each atom _______________ from 1 to 8.

4. The physical state at room temperature changes from __________ to ___________

18 | P a g e

The measurement of the strength

atom to attract electrons towards

its nucleus


19/47

19 | P a g e


20/47

7. The oxides of elements change from basic to acidic properties.

\ Example:

ONa2 ,MgO , 32OAl , 2SiO 104OP 2SO 72OCl

Below are some oxides of elements of Period 3.

(a). Which of these oxides can react with

(i) dilute nitric acid, 3HNO ?________________________________________(ii) sodium hydroxide, NaOHsolution?_______________________________

(b). Based on your answers in (a), what inferences can you make about the

properties of each of the oxides?

_______________________________________________________________

The above show the symbols of lithium, carbon and fluorine.

(a). Which period in the Periodic Table can you find the three elements? Explain.

_______________________________________________________________

(b).Arrange the three elements in order of increasing atomic size.

_______________________________________________________________

(c). Compare the electronegativity of the three elements. Explain your answer.

_______________________________________________________________

_______________________________________________________________

4.6 Transition Elements

elements from Group _____ to Group ________ in the Periodic Table

all are ________________

___________ melting and boiling points ; ____________ densities

good conductors of ___________ and _______________.

** exhibit three special characteristics:1. transition elements show _ _______________________________ in their compounds.

Example: Iron: 2 oxidation numbers _______________________Copper: 2 oxidation numbers

20 | P a g e

*Sodium oxide, ONa2 *Silicon (IV) oxide, 2SiO

*Aluminium oxide, 32OAl *Sulphur dioxide, 2SO

From NaAl, they are

metals, Si is semi metal andP, S, Cl are non-metals

Metal oxides exhibit basic properties and the

non-metal oxide exhibit acidic properties!

can be used to

________ the acid

solutions!

Shows _____

acidic & basic

properties !

So how about

the changes of

metallicproperties? Is it

increase? Ordecrease??

Li73 , C

12

6 , F19

9


21/47

21 | P a g e


22/47

2. transition elements form _______________ ions or compounds.

Example: Cu 2+ - blue MnO4- - purple

Fe2+ - green CrO42- - yellow

Fe3+ - brown

3. transition elements and their compounds are useful catalysts.

Example:

Chemistry Form 4: Chapter 4 - Special Characteristics of Transition Elements

1. Transition elements can form coloured compounds

2. Transition elements have varying oxidation number

Iron has two common oxidation states (+2 and +3) in, for example, Fe2+and Fe3+. It also

has a less common ________ oxidation state in the ferrate(VI) ion, FeO42-.

Manganese has a very wide range of oxidation states in its compounds. For example:

22 | P a g e


23/47

_____________ _____________________

3. Transition elements can form complex ions

A complex ion has a metal ion at its centre with a number of other molecules or ions

surrounding it.

Some examples of complex ions formed by transition metals

[Fe(H2O)6]2+, [Co(NH3)6]2+, [Cr(OH)6]3- , [CuCl4]2-

4. Transition elements can act as catalysts

Iron in the Haber Process

The Haber Process combines hydrogen and nitrogen to make ammonia using an iron catalyst.

Vanadium(V) oxide in the Contact Process

At the heart of the Contact Process is a reaction which converts __________________ into

______________________. Sulphur dioxide gas is passed together with air (as a source of

______________) over a solid _________________________ catalyst.

_______________ in the hydrogenation of C=C bonds

This reaction is at the heart of the manufacture of _______________ from _______________.

However, the simplest example is the reaction between _____________ and __________ in the

presence of a ________________ catalyst.

23 | P a g e

Zinc is usually not classifiedas a transition element

because it does not exhibit

the __________

characteristic of transition

elements!

Precious stones such as______ _____________

______________

______________________

______ are beautiful due to

the colours of the transition

element compounds present

in them!


24/47

Chapter: 4

The Periodic Table of

Elements

4.1 The Periodic Table of Elements

Historical Development of the Periodic Table

** Arrangement of elements in the Periodic Table

a) Elements are arranged in an increasing order of proton number

b)Vertical columns are called group ( Group 1 18)

c) Horizontal rows are called period ( Period 1 7)

d)Elements with similar chemical properties are placed in the same group

e) The group number of the elements with 1 to 2 valence electrons

= the number of valence electrons in its atom.

f)The group number of the elements with 3 to 8 valence electrons= the number of valence electrons in its atom + 10

g)The period number of an element = the number of shells occupied with electrons in its atom.

Complete the table below

Element H11

He4

2Li

7

3 Be9

4B

11

5C12

6N14

7O16

8F19

9Ne

20

10

Electron

arrangement

1 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

Number ofvalence electrons

1 2 1 2 3 4 5 6 7 8

Group 1 18 1 2 13 14 15 16 17 18Number of

shells occupied1 1 2 2 2 2 2 2 2 2

Period 1 1 2 2 2 2 2 2 2 2

Element Na2311

Mg24

12Al27

13 Si28

14P31

15S32

16Cl5.35

17Ar40

18K39

19Ca

40

20

Electron

arrangement

2.8.1 2.8.2 2.8.3 2.8.4 2.8.

5

2.8.

6

2.8.7 2.8.8 2.8.8.

1

2.8.8.2

Number of

valence electrons1 2 3 4 5 6 7 8 1 2

Group 1 2 13 14 15 16 17 18 1 2Number ofshells occupied

3 3 3 3 3 3 3 3 4 4

Period 3 3 3 3 3 3 3 3 4 4

24 | P a g e


25/47

25 | P a g e


26/47

26 | P a g e


27/47

27 | P a g e


28/47

An atom of element E has 10 neutrons. The nucleon number of element E is 19. In

which group and period is element E located in the Periodic Table?

Proton number = 9

Electron arrangement = 2.7Group 17, period 2

An atom of element G has 3 shells occupied with electrons. It is placed in group

17 of the Periodic Table. What is the electron arrangement of atom G?

___2____.____8____.___7_____

4.2 Group 18 Element

known as noble gases: Helium, neon, argon, krypton, xenon & radon

monoatomic

all noble gases are inert chemically unreactive

** The electron arrangement of noble gases are very stable because the

outermost occupied shells are full

Uses of Group 18 elements:

1)Helium gas to fill airships and weather balloons

2)Neon gas used in advertising lights and television tubes3)Argon gas to fill light bulbs

28 | P a g e

Helium has stable duplet electron arrangement. Other noble

gases have stable octet electron arrangement


29/47

4)Krypton gas used in lasers to repair the retina of the eye

7. Radon gas treatment of cancer

8. Xenon gas used for making electron tubes and stroboscopic lamps

29 | P a g e


30/47

30 | P a g e

Neon has stable octet electron arrangement.

So, it does not have to lose, gain or share electrons.

Helium has stable duplet electron arrangement.

Hydrogen is reactive and explode when contact with air.

So, helium is safe and suitable.

Argon has stable octet electron arrangement.

Air contains oxygen which is flammable when contact with heat

So, argon is a safe and suitable choice.

L, M, Q

Because number of shells increases from L, M to Q.

So, the atomic radius increases.

More heat energy is required to overcome to weak Van der

Waals force

L, M,Q have stable octet electron arrangement.

So, it does not have to lose, gain or share electrons to form chemical reaction


31/47

4.3 Group 1 Elements (Alkali Metals)

Lithium, sodium, potassium, rubidium, caesium & francium


d) Lithium batteries in calculator, watches and cameras

e) Sodium - 32CONa in soda-lime glass

f) Potassium - 3KNO as fertiliser.

* physical properties: softmetals, low densities, low melting & boiling points,silvery and shiny surfaces, good conductors of heat and electricity

31 | P a g e


32/47

When going down the Group 1, the melting point and boiling point decrease:

melting & Li

boiling points Na

decrease K

Explain why.__________________________________________________________________

__________________________________________________________________

32 | P a g e


33/47

Chemical Properties of Group 1 Elements

4. react vigorously with water to produce alkaline metal hyrdroxide solutions and hydrogen gas

Example: Li2 + OH22 LiOH2 + 2H

Write down the balanced equation when potassium reacts with water

_______________________________________________________________

5. react (burn) in oxygen gas rapidly to produce white solid metal oxides

Example: Li4 + 2O OLi22

Write down the balanced equation when rubidium reacts with oxygen

_______________________________________________________________

6. burn in chlorine gas 2Cl , to form white solid metal chlorides.

Example: Na2 + 2Cl NaCl2

Write down the balanced equation when potassium reacts with chlorine gas

_______________________________________________________________

** The reactivity of Group 1 elements increases when going down the group.

Explain why.

atomic size increases down the group

Nucleus Attraction force decreases when number of shells increases

Metal bond decreases down the group

Thus, it is Easier to donate the 1 electron valence down the group

When it is easier to lose electron, the higher is the reactivity.

_________________________________________________________

** Potassium reacts more vigorously with water as compared to sodium. Explain.

(Proton number: Na, 11 ; K, 19)

Atomic size of potassium is higher than sodium

The distance between nucleus and electron valence of potassium is bigger so the nucleus attraction force

is weaker.

So the tendency/ easier of potassium to lose the 1 electron valence is higher/greater than sodium atom.

So potassium is more reactive than sodium.

Na (2.8.1) Na + (2.8) + e- ( harder to occur)

K (2.8.8.1) K+ (2.8.8) + e- (easier to occur)

* Safety Precaustion In Handling Group 1 Elements1. All alkali metals must be stored in paraffin oil in bottles.

2. Use forceps to take the alkali metals

3. Wear safety goggles and gloves.

4. A small piece of alkali metal is used when conducting experiments.

To Investigate The Chemical Properties of Lithium, Sidum & Potassium

33 | P a g e

Lithium hydroxide

Lithiumoxide

To prevent the alkali react

with air!


34/47

(C) The Reaction of alkali metals With Water, OH2


they react with water?

Hypothesis: When going down Group 1, alkali metals become more

reactive in their reactions with water.

Variables: Manipulated variable Different types of alkali metals


Fixed variables volume of water, size of metals

Procedure:


2. Dry the oil on the surface of the lithium with filter paper.3. Place the lithium slowly onto the water surface in a trough using a forceps.

4. When the reaction stops, test the solution produced with red litmus paper.

5. Repeat steps 1 to 4 using sodium and potassium to replace lithium one by one

6. Record your observations.

Data & Observation


Lithium Lithium moves randomly and slowly. Form colourless solution. RLP

turns blue.

Sodium Sodium moves rapidly. Produces hissing sound.colourless solution.RLP turns blue

Potassium Potassium moves vigorously. Produce hiss and pop sound. Burn with

reddish-purple flame. Colourless solution. RLP turns blue.

Conclusion: Reactivity increases from lithium to potassium and elements of Group 1

has alkaline properties.

(D)The Reaction of alkali metals With Water , OH2 chlorine / oxygen


they react with oxygen/chlorine?

Hypothesis: When going down Group 1, alkali metals become morereactive in their reactions with oxygen/chlorine.

Variables: Manipulated variable type of alkali metals

34 | P a g e

This procedure also can be

used to test the reaction of

alkali metals with chlorinegas!


35/47


Fixed variables size of metal, content in gas jar

Procedure:


2. Dry the oil on the surface of the lithium with filter paper.

3. Put the lithium in a gas jar spoon and heat strongly until it burns.

4. Transfer the gas jar spoon quickly into a gas jar filled with oxygen gas

5. Observe what happens.

6. When the reaction stops, pour 10cm3 of water into the gas jar. Shake the gas jar.

Test the solution formed with red litmus paper.

7. Repeat steps 1 to 6 using sodium and potassium to replace lithium one by one

8. Record your observations.

Data & Observation

Based on your results, arrange the alkali metals in ascending order of

reactivity.

Lithium, sodium and potassium.Write the chemical equations for the reactions between the products from the

combustion of each alkali metal with water. oxygen

1. 4Li + O2 2Li2O (lithium oxide) / 2Li + Cl2 2LiCl (lithium chloride)

2. ____________________________________________________________

3. ____________________________________________________________

Name the substance formed when caesium reacts with chlorine iodine, I2 gas. Write the chemical

equation for this reaction.

Caesium iodide 2Cs + I2 2CsI

35 | P a g e


Lithium Burns slowly. Red flame. White smoke. White solid.

Sodium Burns vigorously. Yellow flame. White smoke. White solid.

Potassium Burns more vigorously. Reddish-purple flame. White smoke. White

solid.


36/47

4.4 Group 17 Elements (Halogens)

Fluorine, chlorine, bromine, iodine and astatine

uses of Group 17 elements:1) Chlorine water treatment, bleaching agent

2) Bromine weaker bleaching agent

3) Iodine needed in human thyroid gland to produce hormones

*Physical properties: Low melting and boiling points.

Fluorine: pale yellow gas

Chlorine: greenish-yellow gas

Bromine: reddish-brown gas

Iodine: purplish-black gas

*Remember

2Cl melting and colour of Density

2Br boiling points halogens increases

2I increase becomes

darker

36 | P a g e


37/47

37 | P a g e


38/47

38 | P a g e


39/47

When going down the Group 17, the melting and boiling points increase. Explain

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

** Chemical Properties of Group 17 Elements

1) react with water to form two acids

Example: 2Cl + OH2 HCl + HOCl

hydrochloric hypochlorus

acid acid (bleaching)

Write a balanced equation when bromine reacts with water.

Hydrobromic acid hypobromus acid

Hydroiodic acid hypoiodus acid

__________________________________________________________________

2) In gaseous state react with hot iron to form a brown solid, iron (III) halides.Example: Fe2 + 23Br 32FeBr (iron bromide)

Write a balanced equation when iodine vapour reacts with iron

2Fe + 3 I2 2 Fe I3 (iron iodide )

react with sodium hydroxide solution, NaOH, to form sodium halide, sodium halite (I) and

water

Example: 2I + NaOH2 NaI + NaOH + OH2

Write a balanced equation when chlorine reacts with sodium hydroxide solution

__________________________________________________________________

The reactivity of Group 17 elements decreases when going down the group. Explain why.

Number shell increases

When Atomic size increase

Nucleus attraction decrease because the electron valence is further away

Strength to attract an electron to reach stable arrangement decrease

So the reactivity decreases

Chlorine gas reacts more vigorously with hot iron as compared to bromine gas. Explain (Proton

number: Cl, 17 ; Br, 35)

Arrangement of Cl is 2.8.7 and Br: 2.8.18.7

So, Br has 4 electron shells which is more than Cl with 3 electron shells

They have to attract an electron from hot iron to reach stable octet arrangement

The nucleus attraction of Br is weaker because the electron valence is further away

So, reactivity of Cl is higher than Br in reacting with hot iron.

39 | P a g e

Rememberduring the

reactions to form

halides, all halogens are

decolourised

F2is a very

dangerously

reactive

substance!

Do you know why F2

is not used in school

laboratories?


40/47

40 | P a g e

Cl2

gas, Br2

gas and I2

vapour are poisonous!

We must handle them in

a fume chamber!


41/47

To investigate the Chemical properties of Group 17 elements.

The Reaction of halogens with iron


they react with iron?

Hypothesis: When going down Group 17, the halogens become less reactive in

their reactions with iron.

Variables: Manipulated variable Types of halogens

Responding variable Reactivity of halogens

Fixed variable iron

Procedure:

1. Heat the iron wool in the combustion tube strongly2. When the iron wool becomes red hot, pass the chlorine gas over the hot iron wool.

3. Observe any changes and record your observation.

4. Repeat steps 1 to 3 using bromine vapour and iodine vapour to replace chlorine gas one by one.

Data and Observation

Halogens Observation

Chlorine

Iron wool burns brightly and vigorously.

Brown solid are formed.

BromineIron wool burns brightly and lessvigorously. Brown solid are formed

Iodine

Iron wool burns slowly. Brown solid are

formed

What is the function of soda lime in this experiment?

Used to absorb the poisonous gas , chlorine, bromine and iodine gas.

Why must the iron wool be heated first before the halogens are passed over it?

Iron wool is heated to observe the reactivity at faster rate to prevent excessive release ofpoisonous halogen gases.

Name the products for the reactions between chlorine, bromine and iodine with iron. Write the

chemical equations for these reactions

1. Name: iron chloride Equation: 2Fe + 3Cl2 2FeCl3

2. Name: iron bromide Equation:___________________________

3. Name: iron iodide Equation:___________________________

Based on your results, arrange the halogens, 2Cl , 2Br , 2I in ascending order of reactivity.

41 | P a g e


42/47

__________________________________________________________________

Element E is placed below element D in Group 17 of the Periodic Table.

(a). Compare the melting and boiling points of element D with element E. Explain

your answer

Number of shells of E is more than D as atomic size of E is bigger

So, Van der Waal force, the intermolecular force for E is stronger.

More heat is required to overcome the attraction force between particles in E.

So, melting and boiling point of E is higher than D.

(b). Write an equation for the reaction between element D and hot iron

3D2 + 2Fe 2Fe D3

4.5 Elements In A Period

Example: Period 3 in the Periodic Table Properties of Elements

Element Na Mg Al Si P S Cl Ar Proton number 11 12 13 14 15 16 17 18

Electron

arrangement

Atomic radius

(pm)

186 160 143 118 110 104 100 94

Physical state at

room

temperature

Solid Solid Solid Solid Solid Solid Gas Gas

Electronegativity 0.9 1.2 1.5 1.8 2.1 2.5 3.0 -

* Across Period 3:

1. The proton number increases by one unit from one element to the next

element

2. All the atoms of elements have 3 shells occupied with electrons.

3. The number of valence electrons in each atom increases from 1 to 8.

4. The physical state at room temperature changes from solid to gas

42 | P a g e

The measurement of the strength

atom to attract electrons towards

its nucleus


43/47

43 | P a g e


44/47

7. The oxides of elements change from basic to acidic properties.

\ Example:

ONa2 ,MgO , 32OAl , 2SiO 104OP 2SO 72OCl

44 | P a g e

From NaAl, they aremetals, Si is semi metal and

P, S, Cl are non-metals

Metal oxides exhibit basic properties and thenon-metal oxide exhibit acidic properties!

can be used to

neutralize the acid

solutions!

Shows both acidic

& basicproperties !

So how about

the changes of

metallic

properties? Is itincrease? Or

decrease??


45/47

Below are some oxides of elements of Period 3.

(a). Which of these oxides can react with

(i) dilute nitric acid, 3HNO ?_ sodium. Aluminium.

(ii) sodium hydroxide, NaOH solution?___aluminium.. siliconsulphur..

(b). Based on your answers in (a), what inferences can you make about the

properties of each of the oxides?

_sodium oxide is basic oxide

Aluminium oxide is amphoteric oxide

Silicon oxide, sulphur dioxide is acidic oxide

Li : 2.1C: 2.4

F: 2.7

The above show the symbols of lithium, carbon and fluorine.

(a). Which period in the Periodic Table can you find the three elements? Explain.

Period 2, all three have 2 electron shells/ orbits

(b).Arrange the three elements in order of increasing atomic size.

F, C, Li

(c). Compare the electronegativity of the three elements. Explain your answer.Electronegativity increases from Li, C to F.

F has 7 electron valence and the ability to attract an electron valence to reach stable

arrangement increases.

So, F has higher negative charges compared to Li and C.

Electronegativity is the ability to attract electrons.

4.7 Transition Elements

elements from Group 3 to Group 12 in the Periodic Table

all are metals

high melting and boiling points ; high densities

good conductors of heat and electricity.

** exhibit three special characteristics:

1. transition elements show different oxidation numbers in their compounds.

Example: Iron: 2 oxidation numbers +2, +3

Copper: 2 oxidation numbers , +1, +2

45 | P a g e

*Sodium oxide, ONa2 *Silicon (IV) oxide, 2SiO

*Aluminium oxide, 32OAl *Sulphur dioxide, 2SO

Li73 , C

12

6 , F19

9


46/47

2. transition elements form coloured ions or compounds.

Example: Cu 2+ - blue MnO4- - purple, potassium manganate (VII)

Fe2+ - green CrO42- - yellow, Potassium dichromate

Fe3+ - brown

3. transition elements and their compounds are useful catalysts.

Example:

Chemistry Form 4: Chapter 4 - Special Characteristics of Transition Elements

2. Transition elements can form coloured compounds

2. Transition elements have varying oxidation number

Iron has two common oxidation states (+2 and +3) in, for example, Fe2+and Fe3+. It also

has a less common +6 oxidation state in the ferrate(VI) ion, FeO42-.

Manganese has a very wide range of oxidation states in its compounds. For example:

+2 in Mn2+

46 | P a g e


47/47

+3 in Mn2O3

+4 in MnO2

+6 in MnO42-

+7 in MnO4-

3. Transition elements can form complex ions

A complex ion has a metal ion at its centre with a number of other molecules or ions

surrounding it.

Some examples of complex ions formed by transition metals

[Fe(H2O)6]2+, [Co(NH3)6]2+, [Cr(OH)6]3- , [CuCl4]2-

4. Transition elements can act as catalysts

Iron in the Haber Process

The Haber Process combines hydrogen and nitrogen to make ammonia using an iron catalyst.

Vanadium(V) oxide in the Contact Process

At the heart of the Contact Process is a reaction which converts sulphur dioxide into sulphur

trioxide. Sulphur dioxide gas is passed together with air (as a source of oxygen) over a solid

vanadium(V) oxide catalyst.

Nickel in the hydrogenation of C=C bonds

This reaction is at the heart of the manufacture of margarine from vegetable oils.

However, the simplest example is the reaction between ethene and hydrogen in the presence of

a nickel catalyst.

Zinc is usually not

classified as a transitionelement because it does not

exhibit the special

characteristic of transition

elements!

Precious stones such as

emerald, rubies, sapphire and

jade are beautiful due to thecolours of the transition

element compounds present in

them!

CHEMISTRY Form 4 CHAPTER 4-The Periodic Table

Documents

Transcript of CHEMISTRY Form 4 CHAPTER 4-The Periodic Table