CHEMISTRY SPM FORM 4 Short Notes Chapter 4 PERIODIC TABLE OF ELEMENTS

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STUDYSMART CHEMISTRY FORM 4

CHAPTER 4 : PERIODIC TABLE OF ELEMENTS

4.1 Analysing the Periodic Table of Elements 4.2 Analysing Group 18 elements 4.3 Analysing Group 1 elements 4.4 Analysing Group 17 elements 4.5 Analysing elements in a period 4.6 Understanding transition elements 4.1 ANALYSING THE PERIODIC TABLE OF ELEMENTS

Elements in the periodic table are arranged horizontally in increasing ordered.

Two main component of the periodic table are : a) Group b) Period

GROUP

The vertical column of elements in the periodic table arranged according to the number of valance electron in the periodic table are called group.

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There are 18 vertical columns called 1,2,3, until 18

Specific name of group

GROUP 1 Alkali Metal

GROUP 2 Alkali Earth Metal

GROUP 3 to GROUP 12 Transition metals

GROUP 17 Halogens

GROUP 18 Noble Gas

PERIOD

The horizontal row of elements in the Periodic Table consist of the same number of shells occupied with electrons in an elements are called period

There are seven horizontal row of elements know as period 1,2..,7 PERIOD 1 Has 2 elements PERIOD 2 and PERIOD 3 Have 8 elements PERIOD 4 and PERIOD 5 have 18 elements PERIOD 6 has 32 elements PERIOD 7 has 23 elements

Number of valance electron 1 2 3 4 5 6 7 8(except helium)

Group 1 2 3 4 5 6 7 8

ELEMENTS PROTON NUMBER

ELECTRON ARRANGEMENT

NUM OF VALANCE ELECTRON

GROUP NUM OF SHELLS

PERIOD

H 1 1 1 1 1 1

He 2 2 2 18 1 1

Li 3 2.1 1 1 2 2

Be 4 2.2 1 2 2 2

B 5 2.3 3 13 2 2

C 6 2.4 4 14 2 2

N 7 2.5 5 15 2 2

O 8 2.6 6 16 2 2

F 9 2.7 7 17 2 2

Ne 10 2.8 8 18 2 2

Na 11 2.8.1 1 1 3 3

Mg 12 2.8.2 2 2 3 3

Al 13 2.8.3 3 3 3 3

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4.2 ANALYSING GROUP 18 ELEMENTS

Noble gases are monoatomic gases.

These noble gases in group 18 of the Periodic Table make up almost 1% of the air.

All noble gases do not: (a) Dissolve in water, (b) Conduct electricity (c) Conduct heat (d) Monoatomic gases at room temperature.

Except for He, all of the noble gas atoms have 8 electrons in their outer most shells. This arrangement called the octet configuration. Thus, the arrangement of He(with 2 electrons in outer most shells -extremely stable electron arrangement) is duplex electron configuration.

Boiling point and melting point are low because they have very low intermolecular force of attraction (Van der Waals force).

Density is low because the molecules are far apart from each other (big size molecules will have bigger intermolecular forces of attraction).

Low reactivity of noble gases due to unusual high large ionization energies and unusual low electron affinity.

Uses: (a) Helium - super conductors, fill airships and weather balloons, divers tank (80% He, 20% O2), cool metals down. (b) Neon - advertising light (glow red in low pressure tubes), fill television tubes. (c) Argon - fill light bulbs (does not react with tungsten filament), welding (prevent hot metal from reacting with O2 from the air). (d) Krypton - laser surgery, photographic flash lamps. (e) Xenon- lighthouse lamps (blue light), making electron tubes. (f) Radon - cancer treatment.


Group 1 element are known as alkali metal

They are all metals which react with water to form alkaline solution.

All alkali metals are, (a) Solid (b) Silvery and shiny surfaces (c) Soft and melt easily (d) Conductors of electricity

Element Electron Configuration Increase in boiling point, melting point, density, and radius

He 2

Ne 2.8

Ar 2.8.8

Kr 2.8.18.8

Xe 2.8.18.18.8

Ra 2.18.32.8

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The melting points, boiling points and hardness of the atoms decrease down the group because the size of the atoms increases down the group causes the metallic bonding between atoms become weaker.

The radius of the atoms increases down the group because the lower members have more shells of electrons. Thus, mass of atom increases.

The density increases down the group due to its increasing mass and will produce stronger intermolecular attraction. The atoms are closer, resulting in their densities being higher.

Electropositivity is a measure of the ability of an atom to lose its valence electrons. The valence electrons of the lower members are further away from the nucleus, and can be easily donated. Thus, electropositivity increases down the group.

Chemical properties: (a) Reactivity depends on their ability to give away the valence electron (increase down the group). (b) Alkali metals react with oxygen gas to form metal oxides. Example: Na(s) + O2(g) Na2O (c) Alkali metals react with water to form alkaline metal hydroxide solution and hydrogen gas. Example: 2K(s) + 2H2O(l ) 2KOH(aq) + H2(g) d) Alkali metals react with halogen (fluorine, chlorine and bromine) to form colourless, crystalline ionic salts called halides. Example: 2Li(s) + Cl2(g) 2LiCl(s) 2Na(s) + Br2( ) 2NaBr(s) 2K(s) + I2(s) 2KI(s)

Safety precautions: (a) Lithium, sodium, and potassium are highly reactive to water and air, thus must be kept under non-reactive liquid (paraffin oil). (b) Reaction of potassium, rubidium, caesium and francium are explosive. Thus, a small piece should be used always during experiment. (c) Never handle those alkali metals with your fingers because it can react with moist which will form a corrosive hydroxide.

Element

Electron Configuration Decreasing boiling point, melting point, Electro-positivity and hardness. * only radius and density increase

Li

2.1

Na

2.8.1

K

2.8.8.1

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Halogens are diatomic molecules

Halogens are not conductors of heat and electricity.

At room temperature, chlorine is a gas, bromine is a liquid, and iodine is a solid.

Physical properties of halogens a) All are coloured b) Non-metal c) Do not conduct electricity d) Have pungent smell (liquid) e) Poisonous f) Cannot conduct heat

Chemical properties of halogen: (a) Halogens react with heated aluminium to produce powdery solid halides. Example: 3Cl2(g) + 2Al(s) 2AlCl3(s) 3Br2(l ) + 2Al(s) 2AlBr3(s) (b) Halogens react with phosphorus to form phosphorus halides. (c) Halogens react with H2 to form halides. Example: Cl2(g) + H2(s) 2HCl(s) Br2(l ) + H2 (s) 2HBr(s) (d) Halogens react among themselves. Example: I2(s) + Cl2(g) 2HCl(s)

Safety precautions: (a) Vapour of fluorine, chlorine, and bromine are poisonous. (b) Iodine affects negatively the respiration of all living things. (c) Astatine is radioactive. (d) All experiments of halogens should be done inside a fume chamber. (e) Safety goggles and gloves should be used.

Elements Electronic Configuration

Increase in

boiling point,

melting point,

density, and

radius

* Reactivity

decrease

F

2.7

Cl

2.8.7

Br

2.8.8.7

I

2.18.8.7

At

2.8.18.18.8.7

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4.5 ANALYSING ELEMENTS IN A PERIOD

Horizontal rows in the periodic table

There are 7 periods known as period 1,2,3,4,5,6,7

The period number of an elements represent the number of shells occupied with electron in its atom

Period 3 elements

Physical states changes across the period 3 ( From left to right)

Atomic Radius decreases because : a) All the atoms of elements have three shells occupied with electron b) The proton number increased by one unit from one element to the next element c) The number of positive charge in the nucleus increase d) Nuclei attraction on the valance electron increase e) The atomic radius of the elements decrease

Electronegativity increases a) Electronegativity: The strength of an atom in molecules to attract electron toward its nucleus. b) The atomic radius decrease due to the increasing nuclei attraction on the valance electron c) The strength of nucleus to attract electron also increase.

Metallic properties a) Metal, semi-metal (metalloid), and non-metal properties across the period from left to right. b) Metallic properties decreases across the period c) Example : Period 3 : Na, Mg, Al metal Good conductor of electricity The conductivity decrease with increase in temperature

ELEMENTS PROTON NUMBER


NUMBER OF SHELL

PERIOD

Li 3 2.1 2 2

Na 11 2.8.1 3 3

K 19 2.8.8.1 4 4

ELEMENTS Na Mg Al Si P S Cl Ar

PROTON NUMBER

11 12 13 14 15 16 17 18


2.8.1 2.8.2 2.8.3 2.8.4 2.8.5 2.8.6 2.8.7 2.8.8

NUCLEAR CHARGE

+11 +12 +13 +14 +15 +16 +17 +18

RADIUS 0.156 0.136 0.125 0.117 0.110 0.104 0.009 0.001

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Si P, S, Cl, Ar

[Semi-metal] [Non-metal]

-Weak electrical conductivity - Cannot conduct electricity

but increase as temperature rises

-Uses : semiconductor

In brief

Metal Good conductor of electricity and hear, shiny surface, ductile and high melting and boiling point Semi-Metal Not a very good conductor of electricity but conductivity increases as temperature and the presence of impurities such boron and phosphorus (doping) Non-Metal Cannot conduct electricity Basic Oxides Metals oxides that can react with acid to form salt and water Acidic Oxide Non-metal oxides that can react with alkali to form salts and water Amphoteric oxide oxides that can react with both alkali and acid to form salt and water

ELEMENTS Na Mg Al Si P S Cl Ar

METTALIC PROPERTIES (WITH RESPECT TO ELECTRICAL CONDUCTIVITY

Metal

Semi-metal

Non-metal

CHEMICAL PROPERTIES OF OXIDE ( WITH RESPECT TO REACTION WITH ACID AND ALKALI)

Basic oxides

Amphoteric

Oxide

Acidic Oxides

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4.6 UNDERSTANDING TRANSITION ELEMENTS

Properties of transition elements - First transition series are all metals - Transition elements have high melting points - They have high density - They have variable oxidation state, e.g. Iron (Fe) appear as Fe2+ or Fe3+ - They form coloured compounds, e.g. CuSO4 is blue, FeSO4 is green - They form complex ions, e.g. MnO4-, Manganate (VII) ions - They act as catalysts

Uses of transition elements - Most transition elements and their compounds act as catalysts which speed up chemical reactions - Iron is used in Haber Process for manufacture of ammonia - Vanadium (V) oxide is used in contact process to manufacture sulphuric acid - Nickel is used in hydrogenation of alkenes to form saturated fats (e.g. margarine)

Advantage of transition elements - Since transition elements speed up chemical processes in industries, they saves time in manufacture - Less energy is needed for manufacture in industries, hence lower cost - Since less energy is needed, more energy resources can be conserved, e.g. oil to generate electricity in producing iron.

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CHEMISTRY SPM FORM 4 Short Notes Chapter 4 PERIODIC TABLE OF ELEMENTS