Category: Chemistry Notes PPT

What is Terbium?

Terbium is the f-block element. Its atomic number is 65. It is present in the sixth period. The symbol of terbium is Tb. Tb element is silver-white in colour. Terbium electron configuration is [Xe]4f96S2. The electronic configuration of Tb shows that it is the f-block element, as the last electron enters into the f-subshell.

Properties of Terbium

• Terbium is a silver-white element.

• It occurs in the solid-state at standard temperature and pressure.

• It’s melting point is 1629 K.

• Its boiling point is 3396 K.

• Its density is 8.23 g/cm3.

• Its heat of fusion is 10.15 kJ/mol.

• Its heat of vaporization is 391 KJ/mol.

• Its molar heat capacity is 28.91 J/mol.K.

• It shows five oxidation states: 0, +1, +2, +3, +4.

• It is soft, malleable, and ductile in nature.

• Below 219 K temperature, it possesses ferromagnetic properties and above 219 K temperature, it possesses antiferromagnetic properties.

• Terbium being electropositive in nature oxidises when reacts with an acid.

2 Tb (s) + 3 H2SO4 → 2 Tb3+ + 3 SO2−4 + 3 H2↑

8Tb + 7O2 → 2Tb4O7

Uses of Terbium

• Terbium is used as a doping agent in different chemicals like calcium fluoride, strontium molybdate, and calcium tungstate for making solid-state devices.

• Terbium is used in making alloys.

• Terbium is used in electrical devices.

• Its oxide is used in making fluorescent devices.

• It is used in detecting endospores.

Harmful Effects of Terbium

• It acts as an irritant when coming in contact with eyes and skin.

• It is mildly toxic in nature. So, it causes harmful effects in the body when ingested.

Did You Know?

• Terbium is an element which never occurs in free form in nature.

• Important ores of terbium are manazite, bastnasite, and cerite.

• India is one of the main mining areas of terbium.

The elements of the group 13 – 18 come under the p – block elements. In these elements the last electron enters in the outermost p – orbital. They have ns2np1-6 electronic configuration in the valence shell, helium being an exception. These elements show the maximum oxidation state equal to the sum of electrons in the outermost shell or valence shell. Most of the elements of the p – block form covalent compounds although some elements form ionic compounds (such as halogens) and coordination compounds as well. 

 

p-block contains elements which are either metals, non – metals or metalloids. p-block elements include the group of halogens and inert gases. First member of each family of the p-block elements is given below in the table with their general electronic configuration and oxidation states. p-block has the most electronegative element which is fluorine. Elements of p-block generally form acidic oxides. Many elements such as C, Si, Ge, O, N etc. also show phenomenon of allotropy. Property of catenation is also shown by many elements.  

 

Group 17 has a total of five elements such as fluorine, chlorine, bromine, iodine, and astatine. While the initial four are highly reactive and used in a variety of compound formations the last one is a radioactive substance. The entire group 17 is named as halogens in general as they tend to react with metals to produce salts. They consist of 7 electrons in their last shell. 

They are just one electron short to become noble gases which are fulfilled by pairing with other metals. The high reactivity of halogens is what allows them to react with a huge number of elements. It is also seen that in the P-Block Elements: Group 17 Elements there is a metallic nature that increases as we move down the group.

 

 

We have covered the Boron Family (Group -13 elements), the Carbon Family (Group – 14 elements), the Nitrogen Family (Group – 15 elements), and the Oxygen Family (Group – 16 elements) in other articles based on p-block elements. In this article, we will cover the Halogen Family or Group 17 Elements of p-block elements (Class XII, Chemistry). 

 

Group 17 Elements: The Halogen Family 

Group 17 is the fifth group of p-block elements. The word Halogens is made up of two Greek words Halo and genes. Halo means salt and genes mean born, thus halogen means salt producers. All elements of group – 17 produce salts reacting with alkali metals or alkali earth metals. That’s why this group is also known as the Halogen family and these group elements are called halogens. 

 

 

 

 

Anomalous Properties of Fluorine 

• Fluorine differs from other elements of the group – 17 due to its high electronegative character, small size, low F-F bond dissociation enthalpy, and high ionization enthalpy. 

• Fluorine mostly shows exothermic reactions. 

• It forms only one oxoacid while other elements of the group – 17 form many oxoacids. 

• Hydrogen fluoride is liquid while other hydrogen halides are gases. fluorine forms a very strong bond with hydrogen due to its small size and high electronegative nature. 

• d- orbitals are not found in the valence shell of the fluorine atom. 

 

Chlorine 

 

Hydrogen Chloride 

 

Oxoacids of Halogens 

An oxoacid is an acid that contains oxygen. Oxoacids of halogens contain oxygen, hydrogen, and halogen atoms. For example, HOF, HOCl, HOBr, HOI, etc. 

 

Fluorine forms only one oxoacid which is HOF due to its high electronegativity and small size. 

 

Most of the oxoacids of halogens are not stable. They are stable either in an aqueous solution or in the form of their salts. The structure of few oxoacids of chlorine are given below –

 

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Interhalogen Compounds 

Interhalogens compounds are those compounds that are formed by the reaction of two different halogens. They can be assigned general compositions as XX′, XX3′, XX5′, and XX7′ where X is larger size halogen and X′ of smaller size and X is more electropositive than X′. As the ratio between radii of X and X′ increases, the number of atoms per molecule also increases.

 

Group 17 has a total of five elements such as fluorine, chlorine, bromine, iodine, and astatine. While the initial four are highly reactive and used in a variety of compound formations the last one is a radioactive substance. The entire group 17 is named as halogens in general as they tend to react with metals to produce salts. They consist of 7 electrons in their last shell. 

They are just one electron short to become noble gases which are fulfilled by pairing with other metals. The high reactivity of halogens is what allows them to react with a huge number of elements. It is also seen that in the P
-Block Elements: Group 17 Elements there is a metallic nature that increases as we move down the group.

Fun facts about halogens

1. The name halogen arises from two Greek names Hals which means salt and gen which means to make.

2. Fluorine gas is highly dangerous and just breathing about 0.1 percent of it will kill a person.

3. Simple compounds which consist of halogens are called halides

4. Bromine has a very strong bad odor which gets its name from bromos which means stench in the Greek language.

5. The first element of group 17 that was found out was Chlorine.

6. Astatine even though radioactive has great uses in medicine.

This is all about the P-block elements and their physical and chemical properties. Follow the explanation given here in simple language to develop your concepts regarding these elements in the Periodic Table.

Thulium is a chemical element which is a member of the Lanthanide series and is placed in the 6th period. Symbol of the thulium element is Tm. It is a metal which is traditionally considered to be one of the rare earth metals. It’s atomic number 69. Mendelevium which is a member of the actinide series is placed below thulium in the periodic table. Another metal erbium is found at the left of thulium and ytterbium is present at the right of it in the sixth period of the periodic table. Erbium and ytterbium metals are also members of the Lanthanide series. Thulium is a member of f – block element. It is the least common rare earth metal. It is found in earth’s crust. For every kg of earth’s crust its occurrence is 500 micrograms. In soil its occurrence is 0.5 parts per million. It exists in concentrations of 1 part per trillion by moles in the solar system. 

Thulium was discovered by Swedish Chemist Per Teodor Cleve in 1879. He discovered it by removing the contaminants from the oxides of rare earth elements. He took erbia (Erbium oxide) and started to remove impurities from it. During his study, he obtained two new substances. One new substance was brown in color, he named it holmia. Holmia is an oxide of the element holmium. Another new substance was green in color and was oxide of another new unknown element. Per Teodor Cleve named this unknown new element thulium and its oxide thulia. 

The word thulium is taken from the Greek word ‘thule’ which is the name of an ancient Greek place. It is associated with Iceland. In ancient Greek and Roman literature, thule is the farthest north location. British chemist Charles James was the first chemist who obtained pure thulium. 

Thulium is not found in pure elemental form in nature as it is a least abundant rare earth metal. Its most common oxidation state is +3 like other lanthanides and rare earth metals. It has a silvery grey appearance and it’s not a hard metal. It can be cut by a knife. It is ductile and shows resistance to corrosion. 

Thulium has various isotopes ranging from thulium -145 to thulium – 179. Its most stable isotope which is found abundantly is thulium – 169. It is predicted to undergo – decay and forms 165Ho with a very long half life period. Its synthetic isotope thulium – 171 is also very stable with a half life of 1.92 years. Other synthetic isotopes such as thulium – 167, thulium – 168, thulium – 170 have half – life periods of 9.25 days, 93.1 days and 128.6 days respectively.  

Thulium Atomic Number and Electronic Configuration 

It is the least abundant rare earth metal. Atomic number of thulium is 69. Its electronic configuration is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f13 5d0 6s2 or it can be written as [Xe] 4f13 6s2. It has 2 electrons in K – shell, 8 electrons in L – shell, 18 electrons in M – shell and 31 electrons in its outermost shell N, 8 electrons in O shell and 2 electrons in P shell. 

Properties of Thulium

Physical and Chemical Properties – Physical and chemical properties of thulium are listed below –

• Pure thulium is a silvery grey lustrous metal. 

• It tarnishes on exposure to air although it is resistant to corrosion and tarnishes very slowly.

• It is a soft metal.

• It is malleable and ductile. 

• It shows ferromagnetic, antiferromagnetic and paramagnetic properties at specific temperatures. At 32 K, it shows ferromagnetic character while at 32 – 56 K, it shows antiferromagnetic properties. At above 56 K temperature, it is paramagnetic. 

• It has two major allotropes – alpha thulium and beta thulium. Alpha thulium has tetragonal shape while beta thulium has hexagonal shape. 

• It has 69 protons in its nucleus. 

• It is found in solid phase at room temperature. 

• Its melting point is 1545 ℃.

• Its boiling point is 1950 ℃.

• According to the Pauling scale, its electronegativity is 1.25. 

•  Its oxides are basic in nature. 

• It shows hexagonal close packed crystal structure. 

• Its first ionization energy is 596.7 kJ.mol-1.

• On reaction with chalcogens, it forms thulium chalcogenides. 

• Reaction with oxygen – Thulium burns easily at 150 ℃ temperature and forms its oxide Tm2O3. Reaction is given below –

4Tm + 3O2 → 2Tm2O3

2Tm(s) + 6H2O(l) → 2Tm(OH)3(aq) + 3H2(g)

• Reaction with halides – It reacts with halogens and forms thulium halides. It forms different colored halides with different halogens. For example, thulium fluoride is white in color while thulium iodide is yellow in color. In these reactions of thulium with halogens temperature plays a key role. At room temperature thulium reacts with halogens slowly while at higher temperature (> 200 ℃) it reacts with halogens vigorously. Reactions are given below –

2Tm(s) + 3F2(g) → 2TmF3 (s) 

                              white

2Tm(s) + 3Cl2(g) → 2 TmCl3 (s) 

                                  yellow

2Tm(s) + 3Br2(g) → 2 TmBr3 (s)

                                  white

2Tm(s) + 3I2(g) → 2 TmI3 (s) 

                              Yellow

2Tm(s) + 3H2SO4(aq) → 2Tm3+ (aq) + 3SO2−4 (aq) + 3H2(g)

TmCl2 + H2O 🡪 Tm(OH)3 + H2

Tm + 2HCl 🡪 TmCl2 + H2

Applications of Thulium 

Thulium is an expensive and least abundant rare earth metal. So, it has a few applications. Its uses are listed below –

• It is used in lasers as an active laser medium material with holmium, chromium and yttrium aluminium garnet. It can lase at 2080 nm and is used in military applications, medicines, meteorology etc. 

• It is used as an X – ray source. These types of X-ray devices are used in medical and dental diagnosis. 170Tm is being used in X – ray devices for cancer treatment. 

• 170Tm is used for industrial radiography. 

• It is used in high temperature superconductors. 

• It can be used in ceramic magnetic materials which are used in microwaves. 

• It can be used in electricity generating windows which work on the principle of a luminescent solar concentrator. 

Effects on Health 

Thulium is very less toxic but at higher concentrations it can be dangerous. Although insoluble thulium salts are completely nontoxic. It can cause damage to the liver and spleen. Inhalation or ingestion of thulium dust is very harmful. It can cause explosions. 

Thulium: Summary in Tabular Form 

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What is Toluene?

Toluene is a transparent, colourless liquid with an odour similar to benzene. Toluene’s chemical formula is C6H5CH3.

The chemical compound toluene is naturally occurring and mainly derived from petroleum or petrochemical processes. The toluene chemical is present in gasoline, glues, and paints. The liquid toluene smells like paint thinners, is colourless and insoluble in water. It’s a mono-substituted colourless liquid that has a CH3 group attached to a phenyl group. 

The Properties of Toluene

In comparison with benzene, toluene is more electrophilic. It reacts in the same position with normal fragrance due to the greater percentage of methyl group than electron-releasing properties. Chlorotoluene undergoes sulfonation to produce p-toluene sulfonic acid, which then undergoes chlorination by Cl2 in the presence of FeCl3 to yield ortho and para isomers.

 

 

Structure of Toluene

Paints and glues are both manufactured with toluene as a solvent. Toluene is used extensively as a chemical raw material.

Production of Toluene

As a by-product of gasoline production, toluene can also be found naturally in crude oil. Toluene is also produced as a by-product of coal cooking.

Toluene can be produced at a low cost at industrial levels. There are several ways to synthesise it. Toluene is obtained from the reaction between benzene and methyl chloride in the presence of Lewis acid.

C6H5H + CH3Cl → C6H5CH3 + HCl

Chemical Properties

Toluene exhibits electrophilic aromatic substitution reactions similar to those of normal aromatic hydrocarbons. Toluene has a greater capacity for releasing electrons than hydrogen atoms in the same position because of the methyl group present in it. Compared to benzene, methyl is more electrophilic. In the presence of FeCl2, it is chlorinated by Cl2 with sulfonation to give chlorotoluene sulfonic acid, and by sulfonation to give para- and ortho-isomers of chlorotoluene.

A significant factor affecting toluene’s oxidative capacity is its methyl side chain. Benzaldehyde is produced by combining the compound with potassium permanganate and chromyl chloride. This is known as the Étard reaction.

The methyl group is halogenated in the presence of free radicals. As an example, N-Bromosuccinimide (NBS) yields benzyl bromide in the presence of AIBN when heated with toluene. Bromination of toluene with HBr and H2O2 is also possible by using light and HBr.

C6H5CH3 + Br2 → C6H5CH2Br + HBr 

C6H5CH2Br + Br2 → C6H 5CHBr2 + HBr

A strong base will deprotonate the methyl group; the pKa is estimated to be around 41. The methylcyclohexane is formed by hydrogenation. Hydrogen pressure and a catalyst are required.

Uses of Toluene

Benzene can be synthesised from toluene. Toluene reacts with hydrogen gas according to the chemical equation below.

C6H5CH3 + H2 → C6H6 + CH4

In contrast, benzene and xylene are used for the second most common application.

Chemicals that are Produced from Toluene

Benzene and xylene are synthesised using toluene as well as the following chemical reactions:

The Use of Toluene as a Solvent

Solvents commonly made with toluene include:

• Glues

• Paints

• Paint Thinners

• Printing Ink

• Rubber

• Leather Tanners

• Silicone Sealants

• Chemical Reactants

• Lacquers

• Disinfectants.

Toluene’s Other Applications

Internal combustion engines can run on it as gasoline fuel.

Toluene’s Niche Applications

Carbon nanomaterials, nanotubes, and whole rods are dissolved in it.

Commercial Preparation of Toluene

From Coal Tar:

Light oil fraction of coal tar is the primary source of commercial production of toluene. The light oil fraction is washed with conc. H2SO4 in order to remove the bases present in it, then with NaOH to remove acidic substances and finally with water.

It is subjected to fractional distillation. The vapours collected between 80 – 110oC is 90% benzol it contains 70 – 80% benzene and 14 – 24% toluene. 90% benzol is again distilled, and the part distilling between 108 – 1100C is collected as toluene.

Preparation of Toluene from Methylcyclohexane and N-Heptane

It is also obtained by cyclization of n-heptane followed by an aromatization.

Reactions of Toluene

1. Oxidation of Toluene

As toluene is an aromatic compound, it is less susceptible to an oxidation reaction. The methyl group of toluene is a side chain in the aromatic ring structure and is oxidised to the carboxyl group in the presence of a strong oxidising agent.

The oxidation of toluene forms benzaldehyde which can further be oxidised to form benzoic acid. There are many oxidising agents like potassium permanganate.

2. Bromination of Toluene

The reaction of toluene with bromine is known as bromination of toluene. The bromination of it can take place either on the side chain or an aromatic ring. 

Both bromination reactions occur with a different mechanism. Generally, side chain by free radical mechanism and aromatic bromination follows electrophilic substitution mechanism.

3. Nitration of Toluene

Introduction of a nitro group into toluene forms ortho-toluene & para-toluene and the reaction is called nitration of toluene.

The reaction follows the electrophilic substitution mechanism, and the mixture of concentrated sulfuric and nitric acid behaves as a nitrating agent.

In this case, concentrated sulfuric acid acts as a catalyst and generates a nitronium ion which behaves as an electrophile.

Nitronium ions attack on aromatic rings, majorly at ortho and para positions which further form ortho and para-products.

Due to the presence of a methyl group on the ring of toluene, the nitration of toluene is around twenty-five times faster than benzene. As the methyl group is activating towards the -ortho and -para directing groups, hence the nitration of toluene gives poly substituted nitro-products. 

However, the use of low temperature can prevent the substitution of more than one nitro group on the aromatic ring.

Note:

Under normal conditions, toluene gives all three isomers, out of which ortho-derivative forms around 63 % and 34% of para-product and 3% of meta-product is formed.

High yield of ortho products can be explained by the resonating structure of the arenium ion which forms as an intermediate.

Alkynes are the organic molecule that contains triple bonds between the carbon atoms. Its general formula is C_nH_2n-2. They are also known as acetylenes. In this article, we will deal with the structure of alkynes. Alkynes are the most common term studied by the students in general organic chemistry.

Structure of Alkynes

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Triple bond in alkynes shows the following features:

• The hybridization of triple bonded carbon in alkyne is SP.

• The bond angle between the two SP hybridised carbon is 180 degrees.

• The bond length of the triple bond in alkynes is  121 picometer.

• Cyclic alkynes exist rarely in nature.

• The bond strength of alkyne is highest among the saturated (alkanes) and unsaturated hydrocarbons (alkenes and alkynes).

• Triple bond of alkynes is made up of one sigma and two pi bonds.

Properties of Alkynes

Physical Properties

• Alkynes are non-polar, unsaturated hydrocarbons.

• Alkynes are highly soluble in organic and non-polar solvents and slightly soluble in polar solvents.

• Compared to other hydrocarbons like alkanes and alkenes, alkynes have a high boiling point.

• Alkynes in a reaction release a high amount of energy due to the repulsion of electrons.

• Alkynes are more acidic than alkanes and alkenes due to SP hybridisation.

Chemical Properties

The triple bond in alkynes makes it an unstable molecule. Due to its instability, it becomes reactive and undergoes several reactions.

1. Hydrogenation – Alkynes undergoes two types of hydrogenation reactions. Complete hydrogenation (in presence of Pd-C/ H₂) and partial hydrogenation (in presence of Linder’s catalyst/H₂).

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2. It can act as a strong nucleophile by converting into acetylide. 

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3. Alkynes can react with BH₃ and undergo hydroboration reactions to form aldehydes and ketones.

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4. Alkynes undergo halogenation reactions in the presence of different halogenating agents by different mechanisms and forms haloalkanes.

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Did You Know?

• Alkynes are commonly used as fruits ripener.

• Most of the alkynes are used for making organic solvent.

• Alkynes are used as rocket fuel.

• PVC is a polymer made up of an alkyne.

Matter undergoes three different types of changes: physical changes, chemical changes, and nuclear changes. From these changes, the composition of a substance is not altered by physical changes, such as freezing and evaporation. Chemical changes, or in reactions, the formation of new substances are formed. These substances are formed when bonds are formed or broken. 

Types of Chemical Reactions Experiment

The types of chemical reaction experiment depend upon the reactivity of the chemicals. The types of reaction experiments are:

1. Combination reaction (Synthesis reaction experiment)

2. Decomposition reaction

3. Single displacement reaction experiment (Single replacement reaction)

4. Combustion reaction

Combination Reaction- 

In this reaction, two or more two molecules react (combine) and form a single new compound. This type of reaction experiment is also called a synthesis reaction experiment. One combination reaction represents the combination of two or more elements or molecules for the purpose of product formation. Synthesis reaction experiment can be represented as:

A + B → AB

Example: Formation of sodium chloride salt (NaCl) 

2 Na (s) + Cl2 (g) → 2NaCl (s) 

Reaction of elements with oxygen. Metal and non-metals react readily with the free oxygen and form oxides.

2 Mg (S) + O2 (g) → 2MgO (s)

Decomposition Reaction– 

In this type of reaction, complex compounds break into simpler ones. For this reaction, a source of energy is required to break the existing bonds of the complex compound. Decomposition reaction represents the breaking down of the complex compound bond for the formation of simpler compounds. This type of reaction can be represented as 

AB → A + B

This type of reaction occurs in the presence of light, heat, or electricity. When the binary compound is decomposed to form a product, it is called a simple decomposition reaction.  

2 HgO (s) → 2 Hg (l) + O2 (g)

In the decomposition reaction, the reactant can get converted into either elemental form or compound form. In the decomposition of calcium carbonate (CaCO3), calcium oxide and carbon dioxide molecule is formed as a product. Bases or alkalis get decomposed on heating.

2 NaOH (s) + Na2O (s) + H2O (g)

Single Displacement Reaction Experiment-

In this type of reaction one element of the reactant replaces the similar type of element of the different reactant compound. This type of reaction is also known as a single replacement reaction experiment. This type of reaction depends upon the reactivity of the elements. Highly reactive elements replace low reactive elements. Single displacement reaction experiment can be represented as:

A + BC → AC + B

Example: Mg (s) + Cu(NO3)2 (aq) → Mg(NO3)2 (aq) + Cu (s)

The above reaction represents that magnesium is more reactive than copper. Therefore, magnesium replaces copper. 

Combustion Reaction- 

Combustion reaction is a type of reaction in which reactants react with oxygen and release energy or heat in the surrounding. A combustion reaction takes place in the presence of oxygen. This type of reaction can be of two types: 

• Incomplete combustion

• Complete combustion

Organic compounds when undergoes complete combustion produces carbon dioxide, water molecules in the gaseous state, and energy. 

C3H8 (g) +5 O2 (g) → 3 CO2 (g) + 4 H2O (g)

Generally, hydrocarbons are used in combustion reactions for energy production. A combustion reaction is an exothermic reaction.

Double Displacement Reaction–

In these types of chemical reactions experiment the positive ions (cation) and negative ions (anion) exchange their position to form new compounds. Double displacement reactions generally occur in an ionic compound. Double displacement reaction is represented as:

AB + CD → AD + CB

In the above reaction, AB and CD are ionic compounds. In AB A is a cation and B is an anion. In CD C is a cation and D is an anion.

Comparison of Single Replacement Reaction Experiment and Double Displacement Reaction

In a single replacement reaction experiment, only one element replaces the other in the two reactants, depending upon the reactivity. While in a double displacement reaction reactants exchange the cation or anion of the two ionic compounds. In a single replacement reaction experiment, both elemental state and ionic state can participate. While in a double displacement reaction only ionic compounds can participate.

Did You Know?

• You may think that chemical reaction occurs only in the laboratories, but it also occurs in the human body, plants, and the environment.

• All types of chemical reactions do not occur at the same rate. Some reaction completes in a few minutes and some get completed in years.

• The rate of a chemical reaction can be altered by the addition of a catalyst.

• In physical changes, no chemical reaction occurs.

• When a single reaction completes in the series of the reaction, it is termed a chain reaction.