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group 18

Posted by seorang insan On Friday, July 9, 2010 0 comments

Introduction

Group-18:Noble Gas

The "Noble Gases" are the last group in the Periodic Table, they also known as "inert gas", due to their non-reactive behavior.
As shown in the diagram on the right, this group consist of six elements, namely Helium, Neon, Argon, Kripton, Xenon and Radon.
They are non-metallic, colourless gases at room temperature and pressure with very low melting points and boiling points.
They form 1% of air, and most of this is argon.

Physical Properties

Name	Proton number	Electron arrangement	Melting point	Boiling point
Helium	2	2	-270^oC	-269^oC
Neon	10	2.8	-249^oC	-246^oC
Argon	18	2.8.8	-189^oC	-186^oC
Krypton	36	2.8.18.8	-157^oC	-152^oC
Xenon	54	2.8.18.18.8	-112^oC	-108^oC
Radon	86	2.8.18.32.18.8	-71^oC	-62^oC

The table above shows the physical properties of the noble gas.
The size of atom increases down the group, due to the increase number of electron shell.

Solubility an Conductivity

All noble gas are insoluble in water.
They are not conductor of heat and electricity.

Melting Point and Boiling Point

As show in the table above, the melting and boiling point of noble gases are very low.
This is because all noble gases exist as monoatoms. The force in between all these atoms is the weak van de Waals' Force.
Therefore very little energy is needed to overcome this force during melting and boiling.

Changes Down the Group

The melting and boiling point increase down the group.
This is because the size of the atom increases down the group.
The strength of van de Waals force increases as the size of the particles (atoms) increases.
More energy is needed to overcome the force in between the atoms during melting and boiling, hence the melting and boiling point become higher.

Density

The density of noble gases are very low.
Nevertheless, the density increases steadily down the group.
Density of a substance is given by the equation $Density = \frac{{Mass}}{{Volume}}$ .
Down the group, both the mass and the volume increase, but increase of mass is faster than the volume, hence the density increases down the group.

Chemical Properties

All the noble gases are non-reactive elements.
This is because their valence shell is full of electrons.
In the chemical world, an atom is in the chemically most stable state if their valence shell is full with eight electrons (or 2 electrons for the first shell.).
Therefore all noble gases do not react with other elements, due to their stable electronic structure. (We will discuss in more detail in the very next chapter, the Chemical Bond.)
They exist as single atoms, that is they are monatomic.

All elements in Group 18 are very stable and do not react with themselves or other elements to form any molecule or compound.

All elements in Group 18 exist as monoatoms.

Uses of the Group 18 (Noble Gases)

Helium

Airship

The gas is much less dense than air. Therefore it is used in balloons and 'airships'.
Because of its inertness it doesn't burn in air UNLIKE hydrogen which used to be used in large balloons with 'flammable' consequences.

Airship

Deep-sea Diving

Helium is also used in gas mixtures for deep-sea divers.
This is because the solubility of the helium is very low. Therefore it will not dissolve in the blood even though the pressure of the surrounding is very high.

Deep-sea diving

Neon

Neon emits light when high voltage electricity is passed through it.
Because of this, it is used in glowing 'neon' advertising signs and fluorescent lights.

Neon Tube

Argon

Filament Bulb Argon, like all the Noble Gases is chemically inert. It used in filament bulbs because the metal filament will not burn in Argon and it reduces evaporation of the metal filament.	filament bulb
Welding Argon also used to produce an inert atmosphere in high temperature metallurgical processes, eg in welding where it reduces brittle oxide formation reducing the weld quality.	welding
Fire Extinguisher Argon is also used for extinguishing fires where damage to equipment is to be avoided
Argon bubbles are used to stir mixtures in steel production. Argon is the cheapest to produce.

Krypton

Krypton is used in fluorescent bulbs, flash bulbs and laser beams.

Fluorescent Bulb

Flash Bulb

Xenon

Also used in fluorescent bulbs, flash bulbs and lasers.

Radon

Almost no uses!

History of Periodic Table

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History of Periodic Table

Antoine Lavoisier

Antoine Lavoisier is believed to be the first scientist who classify elements into a few groups.
The following table shows the classification of elements (Including light and heat) given by Antoine Lavoisier.
In his table, he differentiated metal and non-metal.
He had mistakenly classified light and heat as matter and baryta (barium hydroxide), lime and silica as element.

Group 1	Graup 2	Group 3	Group 4
Hydrogen Nitrogen Oxygen Light Heat	Carbon Sulphur Fluorine Chlorine Phosphorus	Arsenic Silver Bismuth Cobalt Lead Zinc Nickel Tin	Aluminium Baryta Lime Silica Magnesia

Johann Dobereiner--Law of Triads

Johann Dobereiner

In 1817 Johann Dobereiner noticed that the atomic weight of strontium is equal to the average atomic weight of calcium and barium, and these 3 elements possessing similar chemical properties.
He grouped these 3 elements together and name it as a triad.
In 1829, he discoverd 2 more triads: the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad of lithium, sodium and potassium.
After this discovery, he proposed that nature contained triads of elements, and named this as the Law of Triads.
According to the Law of Triads, the atomic mass of the middle element is equals to the average of the other two members and all 3 elements show similar chemical properties.
The table below shows the example of triads found by Dobereiner.

Alkali triad:	Earth Alkali triad	Halogen Triad
Lithium, Sodium, Potassium	Barium, Calcium, Strontium	Chlorine' Bromine, Iodine

John Newlands-Law of Octaves

In 1864, John Newlands arranged the elements according to the ascending order of their atomic mass, and managed to publish his version of periodic table.
He grouped the elements together base on their chemical properties and found that the chemical properties of element changes when the atomic mass increases but similar chemical properties will repeat every 7 elements.
For example, he found that the chemical properties of the 8th element is equals to the 1st element, and the chemical properties of the 9th element is equals to the 2nd.
Base on this discovery, he proposed the Law of Octaves (by analogy with the seven intervals of the musical scale).
This law stated that any given element will exhibit similar chemical properties to the eighth element following it in the table.

Lothar Meyer-Meyer’s Curve

Lothar Meyer

Meyer estimated the volume of atom by using an equation ${\rm Volume\ of\ Atom\ of\ an\ element = }\frac{{{\rm mass\ of\ 1\ mole\ of\ atoms\ of\ the\ element}}}{{{\rm density\ of\ the\ element}}}$ .
He plotted the atomic volumes of the elements against the atomic weight, and found that the chemical properties of the element recur periodically.
He also notice that the elements occupying the corresponding position of the curve show similar chemical properties.
For example, all the elements located at the peak of the graph (Lithium, sodium and potassium)show similar chemical properties.
In 1868, Meyer constructed a periodic table which he gave to a colleague for evaluation. (This may be consider as the first but not published periodic table.)
Unfortunately for Meyer, Mendeleev's table became available to the scientific community via publication (1869) before Meyer's appeared (1870).

An introduction to Lothar Meyer's Atomic Volume Curve

Julius Lothar Meyer – the first identifier of periodicity?
More detail discussion on Meyer's Periodic table

Mendeleev-First Periodic Table

Mendeleev

Mendeleev published his periodic table & law in 1869.
He arrange the elements according to the ascending order of atomic mass and put all the elements that have same chemical properties in the same group.
He left empty space in the periodic table for elements that haven't been discovery at that time.
Although he arranged the elements in ascending order of the atomic mass, he changed the order if the chemical properties of the element did not match its group.
From the empty space present in his table, he even predicted the existence and properties of unknown elements which he called eka-aluminum, eka-boron, and eka-silicon.
Later when elements gallium, scandium and germanium were found, scientist found that Mendeleev's prediction was excellently accurate.
Comparison of Mendeleev's prediction of eka-aluminium with later found galium is shown in the table below.

	Eka-aluminium (Ea)	Gallium (Ga)
Atomic weight	About 68	69.72
Density of solid	6.0 g/cm³	5.9 g/cm³
Melting point	low	29.78^oC
Valency	3	3
Oxide	Formula Ea₂O₃, density 5.5 g/cm³. Soluble in both acids and alkalis.	Formula Ga₂O₃, density 5.88 g/cm₃. Soluble in both acids and alkalis.

H.J.G. Moseley-Modernized the Periodic Table

Henry Moseley

Moseley managed to measure the proton number of atoms.
He then arranged the elements in the periodic table according to the ascending order of the atomic number (proton number), but not the atomic mass, as done by Mendeleev.
This correction was considered as a very important step in modernisation of periodic table.

He managed to predict the existence of four undiscovered elements from the proton number.

Modern Periodic Table

The idea of the Periodic Table is to arrange the elements in a way that enables chemists to understand patterns in the properties of the elements.
According to www.webelements.com, there are 118 known elements now.
Part of it exist in the nature, the others were synthetic elements.
In modern periodic table, the elements are arranged in ascending order of Atomic(proton) Number.
The vertical columns of the periodic table is called GROUP whereas the horizontal rows is called the PERIOD.

Group

The vertical columns of the periodic table is called Group.
There are 18 groups in the periodic table.
All the elements in the same group have same number of valence electron.
Since the chemical properties of an element is determined by its electron arrangement, particularly the number of valence electron(s). Thus, elements in the same group exhibit similar chemical properties.
Nevertheless, the reactivity of the elements in the same group changes when move down the group.
The elements in most of the groups (but not all) also exhibit similar physical properties, and the physical properties varies gradually down the group.

Name of the Group

The Group is named according to their position in the periodic table. For example, the first group is called Group 1, the second group is called Group 2 and so on.
Group 3 to Group 12 are categorised to another big group, called the Transition Metal Group.
Group 1, 2, 17 and 18 have trivial name, as shown in the table below.

Group	Trivial Name
Group 1	The Alkali Metals
Group 2	The Earth Alkaline Metals
Group 17	The Halogens
Group 18	The Noble Gases

Period

The horizontal rows is called the PERIOD.
There are 7 periods in period table.
The first period only has 2 elements only.
The second and third period consist of 8 elements, are called the short period.
The forth and the fifth period consist of 18 elements, are called the long period.
The sixth and the seventh period has 32 elements.

Lanthanide and Actinide Series

The sixth period has 32 elements. Due to short of space, 14 elements in the transition metal group are removed from the same horizontal row and is placed below the main table, These elements are called the Lanthanide Series.
The seven period also has 32 elements. With the same reason, 14 elements are removed from the same horizontal row and is placed below the main table, These elements are called the Actinide Series.

Periodic Table and Electronic Configuration

The similarities and differences in the chemical properties of elements can be explained by the electron arrangement of the atoms.
The classification of Group and Period are totally related to the electron arrangement of the atoms. As shown in the table above, *the classification of elements in a periodic table is as follows:

All the elements in a same group have equal number of valence electron(s) (outer most electron)
All the elements in a same period have equal number of electron shell(s) (orbit).

Table below shows the number of valence electron in a different group. In the SPM syllabus, we ignore the arrangement of electron of the transition metal.
For example, the electron arrangement of calcium is 2.8.8.2. It has 2 valence electron and 4 electron shell. Therefore, it is placed in Group 2, period 4.
Hydrogen, the simplest element atom, with 1 electron, does not fit into any group. (Even though some of the periodic table place it in Group 1, due to its 1 (and the only one electron) valence electron.

Number of Valence Electron in a Group
Group	Number of Valence Electron
Group 1	1
Group 2	2
Group 13	3
Group 14	4
Group 15	5
Group 16	6
Group 17	7
Group 18	8

Preparing Standard Solutions

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Preparing Standard Solutions

This page will help you to master the preactical details involved in preparing standard solutions.

Suppose that you need to prepare 500 ml of a 0.050 M solution of sodium chloride.

Preliminary calculations:

A 0.050 M solution will contain 0.050 moles of solute in 1.00 l of solution. Now, sodium chloride has a M_r = 58.44, so the solution will contain 58.44 x 0.050 = 2.922 g.l^-1. Since we only want 500 ml (i.e. ½ l, we will only require 1.461 g of NaCl.

These calculations should be entered in your laboratory workbook.

Equipment and reagents required:

You will need:

Analytical grade sodium chloride.
Distilled water.
A top-loading balance accurate to 0.01 g.
Glassine paper.
A spatula.
A small beaker (50 ml).
A 500 ml volumetric flask
A wash-bottle filled with distilled water.

Method:

Step 1:

Tip about 3 g of the sodium chloride into the small beaker. (As a rule, do not put spatulas into bottles of analytical grade reagents. This is important in order to maintain the purity of their contents. Close the bottle as soon as you have finished with it.

Step 2:

Place a square of glassine paper on the pan of the balance. Adjust the reading to 0.00 g. Using the spatula, gradually add small quantities of the sodium chloride from the beaker until a reading of 1.46 g is obtained. Switch off the balance. Make sure that no reagent has been spilled onto the pan. If you seen any reagent, clean the pan and start over.

Step 3:

Pour the contents of the glassine paper CAREFULLY into the volumetric flask. If any crystals stick to the paper, wash them in with the wash bottle.

Step 4:

Add about 200 ml distilled water to the flask, and swirl it gently until all crystals are dissolved.

Step 5:

Add distilled water carefully up to 2-3 cm below the mark on the flask. Make up to the final volume with the wash-bottle (Do not overfill!). Stopper the flask and turn it upside down a few times to thorougly mix the contents.

Step 6:

Pour the contents of the flask into a clean, dry blue-top reagent bottle.

Make sure that you label the bottle with its contents, your name, and date of preparation.

Stock solutions:

Rather than preparing small quantities of a standard solution every time you require it, it is better to prepare a relatively large volume of a concentrated stock solution, and dilute it as required. For example, suppose you have made up 2 l of a 3 M sodium carbonate solution, as described above. Then, if you need 100 ml of a 0.01 M Na₂CO₃ solution, you would need to dilute this solution 300 times:

Pipette 0.33 ml of your stock solution, using a Gilson pipette, into a 100 ml volumetric flask, and make up to the mark with distilled water. Use what you need, and discard the rest.

The use of Gilson pipettes is discussed in the next page.

Serial dilution:

Suppose you have a stock solution of a reagent, at 1.0 M. If you take 1.0 ml of that solution, and dilute it to 10.0 ml in a volumetric flask, you will have a new stock solution which will have 1/10th the concentration of the original solution. This process can be repeated, each time obtaining a solution which is 10 times more dilute than the previous one. Great care must be taken that the volumes are accurately dispensed, as errors increase exponentially as one makes several dilutions in this way.

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PENAMAAN ISOMER ALKENA

Posted by seorang insan On Thursday, July 8, 2010 0 comments

PENAMAAN ISOMER ALKENA

Langkah-langkah berikut digunakan untuk menamakan isomer ini.

Langkah 1:

Pilih rantai karbon terpanjang yang mempunyai ikatan ganda

dua sebagai ikatan alkena induk.

C - C - C = C

Betul : 5 atom karbon

Langkah 2 :

a)Tentukan kedudukan ikatan ganda dua

b)Nomborkan atom karbon bermula dari hujung rantai yang akan

memberi nombor terkecil bagi atom karbon yang

mengandungi ikatan ganda dua.

Langkah 3 : Nyatakan bilangan dan kedudukan kumpulan alkil.Pada

kedudukan terdapat kumpulan metil.

Langkah 4 : berikan nama alkena. tu jee... mudah kan?

CONTOH :

ringkasan Kumpulan Homolog

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Sebatian carbon

1. Pembakaran lengkap sebatian organic dalam oksigen berlebihan menghasilkan karbon dioksida,CO₂ dan air

2. Hidrokarbon ialah sebatian organic yang mengandungi unsure karbon dan hydrogen sahaja.

Isomerism

1. Isomerisme ialah fenomena di mana dua atau lebih molekul mempunyai jenis dan bilangan atom yang sama tetapi susunan atom yang berbeza.

2. Isomer-isomer ialah dua atau lebih molekul yang mempunyai formula molekul yang sama tetapi formula struktur yang berbeza.

Alkana

1.Alkana ialah suatu siri homolog bagi hidrokarbon tepu dengan formula am C_nH_2n+2dengan n = 1,2,3,4…..

2. sifat fizik alkana seperti takat lebur, takat didih dan ketumpatan adalah rendahtetapi semakin meningkat secara beransur-ansur apabila bilangan atom karbon per molekul semakin meningkat.

3. Alkana terbakar dalam udara berlebihan menghasilkan karbon dioksida,CO₂ dan air

4.Alkana menjadi tindak balas penukargantian dengan klorin atau bromine dengan kehadiran cahaya matahari atau cahaya ultralembayung

Alkena

1.alkena ialah suatu siri homolog bagi hidrokarbon tak tepu dengan formula am C _nH_2ndengan n=2,3,4,….

2. Sifat fizik alkena seperti takat lebur,takat didih dan ketumpatan adalah rendahtetapui semakin meningkat secara beransur-ansur apabila bilangan atom karbon per molekul semakin meningkat.

3. Alkena terbakar dalam udara berlebihan menghasilkan karbon dioksida, CO₂ dan air

4. Alkena menjalani tindak balas penambahan dengan bromine,klorin,kalium manganat(VII) berasid,hydrogen,hydrogen halida dan air serta mengalami tindak balas pempolimeran.

5.Alkena menyahwarnakan warna ungu kalium manganat(vii) berasid manakala alkana tidak bertindak balas dengan kedua dua reagen itu.

Alcohol

1.Alkohol ialah suatu siri homolog dengan formula am C_nH_2n+1COOH di mana nilai n=1,2,3,……

2.Ethanol disediakan melalui

· Penapisan karbohidrat oleh yis

· Tindak balas etena dengan stim

3. Alkohol terbakar dengan lengkap dalam udara berlebihan menghasilkan karbon dioksida CO₂air dan haba.

4. Pengoksidaan alcohol menghasilkan asid karboksilik yang sepadan

5. Pendehidratan alcohol menghasilkan alkena yang sepadan dan air

Asid karboksilik

1. Asid karbosilik ialah suatu siri homolog dengan formula amC_nH_2n+1COOH di mana n=1,2……

2. Asid karbosilik bersifat asid dalam air, maka dapat bertindak balas dengan besw, karbonat logam, dan logam reaktif untuk membentuk garam.

3. Asid karbosilik bertindak balas dengan alcohol dengan kehadiran mankin asi sulfurik pekat dalam keadaan panas untuk menghasilkan ester dan air. Tindak balas ini digelar pengesteran

Ester

1. Ester ialah suatu siri homolog dengan formula am

C_nH_2n+1COO_mH_2m+1=0,1,2,3,…….

Dan m= 1,2,3…..

2. Ester ringkas berbau wangi tetapi ester kompleks kurang berbau.

3. Ester digunakan sebagai perisa, bahan pengawet dan pelarut organic.

4. Ester tidak larut dalam air kecuali metal metanoat dan kurang tumpat daripada air.

sebatian karbon

Posted by seorang insan On 0 comments

sebatian karbon

untuk penamaan..

apa yang paling penting sekali kita kena tau asanya..

kena hafal laaa..

pendek jo..

nie namanya imbuhan.. hafal

Bilangan Atom Karbon

Awalan

1 Met

2 Et

3 Prop

4 But

5 Pent

6 Hesk

7 Hept

8 Okt

9 Non

10 Dek

nie kena hafal gak..

KUMpulan alkil

Bilangan atom karbon pada rantai sisi	Formula bagi rantai sisi (kumpulan alkil)	Nama rantai sisi
1	-CH₃	metil
2	-C₂H₅	etil
3	-C₃H₇	propil
4	-C₄H₉	butil
5	-C₅H₁₁	pentil

dan yang ter akhir ..

kumpulan berfungsi ...

Siri homolog	Fomula am	Kumpulan berfungsi
Alkena	C_nH_2n, n=2,3,4….	Ikatan dubel, -c=c-
Alkohol	C_nH_2n+1OH, n=0,1,2….	Kumpulan hidroksil, -OH
Asid karbosilik	C_nH_2n+1COOH, n=0,1,2….	Kumpulan karbosil, -C-OH II O
Ester	C_nH_2n+1COOC_mH_2m+1, n=0,1,2…. m=1,2,3……	Kumpulan karbosilat, -C-O II O

home

Pages

Introduction

Physical Properties

Solubility an Conductivity

Melting Point and Boiling Point

Density

Chemical Properties

Uses of the Group 18 (Noble Gases)

Helium

Airship

Deep-sea Diving

Neon

Argon

Filament Bulb

Welding

Fire Extinguisher

Krypton

Xenon

Radon

History of Periodic Table

Antoine Lavoisier

Johann Dobereiner--Law of Triads

John Newlands-Law of Octaves

Lothar Meyer-Meyer’s Curve

Mendeleev-First Periodic Table

H.J.G. Moseley-Modernized the Periodic Table

Modern Periodic Table

Group

Name of the Group

Period

Lanthanide and Actinide Series

Periodic Table and Electronic Configuration

Preparing Standard Solutions

Preliminary calculations:

Equipment and reagents required:

Method:

Step 1:

Step 2:

Step 3:

Step 4:

Step 5:

Step 6:

Stock solutions:

Serial dilution:

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