Category: Chemistry Notes PPT

Proteins are important biological compounds that have a higher molecular weight. They are probably nature’s most complex organic materials. Plants tend to build their proteins from minerals, carbon dioxide, and water in the presence of sunlight. These compounds are the most abundant organic compounds found in nature. In every living organism, they are present. Animals tend to get their share of proteins from plants. Life is linked with the existence of proteins. 

The proteins are identified by some laboratory tests. These tests are discussed below along with its theory, required material for tests, and observation. The aim of the protein laboratory test is discussed below.

Aim

The aim of this article to perform a total protein lab test for identifying the presence of proteins in the samples given.

Theory

Proteins possess a higher molecular mass of long-chain polymers that consist of α-amino acids. Cells contain proteins and they are therefore present in all living bodies. Proteins consist of carbon, oxygen, nitrogen, hydrogen, and often sulphur and phosphorus. There are a few tests that are carried out for finding the presence of proteins in the samples given. 

These laboratory tests of proteins are:

1. Biuret test

2. Millions test

3. Xanthoproteic test

4. Ninhydrin test

Each of the tests is discussed below along with the chemical reaction involved in the test.

1. Biuret Test

The compounds having peptide linkage undergo the Biuret test. Proteins are known as the polypeptides of amino acids that are linked together by the peptide bonds. A protein alkaline solution is treated with one drop of aqueous copper sulphate and a bluish violet colour is seen.

The Biuret test is useful in the identification of proteins and protein estimation. Biuret is a kind of chemical that is formed when urea gets heated to 180 ℃. During this reaction, two molecules of urea tend to condense and form a biuret or a bi-urea molecule. The biuret reagent forms a complex of violet colour in the presence of copper ions. 

Note: The formation of the violet colour confirms that the proteins are present.

2. Xanthoproteic Test

When proteins are treated with nitric acid, it gives an orange or yellow colour. The concentrated nitric acid gets used for the nitration process. When proteins are treated with nitric acid, it gives a yellow precipitate that later turns to orange colour when it is treated with an alkali.

Note: The appearance of the yellow coloured solution confirms that proteins are present.

3. Millon’s Test

The phenolic group of the tyrosine compound of proteins tends to react to the mercuric sulphate in the presence of sulphuric acid and sodium nitrate and gives a red colour. The Million’s test is done on the proteins that have phenolic amino acids. However, gelatin does not show this test. Initially, a white precipitate is formed when the proteins are treated with the Million’s reagent and they then turn into brick red in colour when boiled. This confirms that proteins are present.

Note: When a brick red solution appears, it confirms the presence of the proteins.

4. Ninhydrin Test

Proteins undergo a reaction with the pyridine solution of ninhydrin to give a coloured solution. This colour ranges from deep blue to violet-pink and even red in a few cases. The ninhydrin solution is prepared when 0.1g of ninhydrin is dissolved in 100ml distilled water. However, this ninhydrin is highly unstable and can only be kept for 2 days. The chemical reaction is as follows.

Note: The appearance of the violet coloured solution confirms that the proteins are present.

Materials Required for the Protein Lab Test 

The list of materials are given below that are required for the protein lab test.

1. Sodium hydroxide

2. Pyridine solution

3. Ninhydrin reagent

4. Copper sulfate solution

5. Nitric acid

6. Sodium nitrite

7. Sulfuric acid

8. Mercuric sulfate

9. Distilled water

10. Dropper

11. Test tubes

12. Test tube holder

13. Stirrer

14. Water bath

Apparatus Setup of the Protein Total Spot Urine Test

Given below is the setup for the test to give low protein lab results.

Procedure

The procedures of the laboratory test of proteins are as follows:.

1. Biuret Test:

• Take the sample given that is to be tested in a test tube.

• Then add 2ml of the sodium hydroxide solution to the sample.

• To this add about 5 to 6 drops of the copper sulfate solution.

• If a bluish violet colour appears, it indicates the presence of the proteins.

2. Xanthoproteic Test:

• Take 2ml of the sample in a clean test tube.

• Add a few drops of the concentrated sulfuric acid to it and then heat.

• If a yellow precipitate is seen to be formed, it confirms the presence of the proteins.

3. Millions Test:

• Take 2ml of sample solution given in a test tube.

• To it add about 2–3 drops of the Millon’s reagent and then shake well.

• Observe any changes.

• If a white precipitate is seen which then changes to brick red when heated, then it confirms the presence of the proteins.

4. Ninhydrin Test:

• Take the given sample solution that is to be tested in a test tube.

• Add about 1–2ml of the ninhydrin solution to it.

• Then boil the mixture and observe any changes.

• If the solution turns blue in colour, then it confirms the presence of the proteins.

Observation and Inference from the Protein Laboratory Test

Results and Discussions

The given sample contains _________ (proteins).

Precautions

1. Handle the chemicals with care when performing the experiments and tests.

2. Wear lab aprons and gloves while performing the experiments.

3. Use only the droppers for taking the reagents from the bottles.

Viva Questions for the Total Protein Lab Test

1. What are proteins?

Answer: Proteins are made of smaller units known as amino acids which are attached in the form of longer chains to one another. Twenty different types of amino acids can be combined together to form a protein molecule.

2. What are the two different types of proteins?

Answer: The two different kinds of proteins are fibrous proteins and globular proteins.

3. What happens when a protein undergoes hydrolysis?

Answer: When proteins undergo the process of hydrolysis, they form α-amino acids.

4. How can amino acids together form a polypeptide?

Answer: Two amino acids get linked together when a water molecule is lost. The amino acids that are joined together by the peptide bonds tend to form a chain of polypeptides and every unit of the amino acids in the polypeptide is referred to as the residue. 

5. What do you mean by the monomer and polymer of the proteins?

Answer: A monomer is referred to as a molecule that forms bigger polymer molecules. It is known to be the building block of proteins. For example, amino acids are the building blocks of proteins. A polymer is known as a protein of the monomer series.

Conclusion

There are many important functions that are performed by proteins which are essential for all forms of life. They are important structural molecules. In this article, we learn all the necessary information of laboratory tests of proteins.

Lead acetate is an ionic compound with the formula [Pb(CH3COO)2], in which lead is present in +2 oxidation state. It is a white crystalline solid. It has a slight sweet taste.  It is also known as Plumbous acetate, salt of Saturn, sugar of lead, Goulard’s powder or lead diacetate. Its systematic IUPAC name is Lead(II) ethanoate. Lead acetate is also toxic like other lead compounds. But it still has various applications such as a fixative and also as a reagent for synthesis of other compounds. It was also used as a sweetener but soon it was banned due to its toxic nature. It was discovered in the US in 1944. 

 

Lead(II) acetate has Pb+2 cation and CH3COO– anion. It is a water – soluble compound. It is commonly found as trihydrate lead acetate which is particularly known as sugar of lead due to its sweet taste. Molecular formula of trihydrate lead acetate is Pb(CH3COO)2.3H2O. It is white in color and a monoclinic crystalline substance which is soluble in water. It is used in dyeing, gold cyanidation plants, paints etc.

 

The formula of Lead(II) Acetate

 

Structure of Lead Acetate 

It is an ionic compound that is formed by the reaction of elemental lead and acetic acid. It has one Pb2+ ion and two CH3COO– ions. As lead cation contains +2 charge while each acetate anion has -1 charge, so the compound lead(II) acetate contains zero charges. 

 

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Properties of Lead Acetate 

Physical and chemical properties of lead acetate – Properties of lead acetate are listed below –

• The molar mass of anhydrous lead acetate is 325.29 g.mol-1.

• The molar mass of its trihydrate (Pb(CH3COO)2.3H2O) form is 379.33 g.mol-1.

• It is a white-colored efflorescent crystalline solid. 

• It is slightly sweet.

• It has a pleasant acetic smell. 

• Its density in its anhydrous form is 3.25 g.cm-3 while in its trihydrate form is 2.55 g.cm-3.

• The melting point of anhydrous lead acetate is 280 °C. While the melting point of trihydrate lead acetate is 75 °C.

• Anhydrous lead acetate is soluble in water and its solubility increases as temperature increases. For example, 19.8 grams of it is soluble in 100ml water at 0 °C while 44.3 grams are soluble in 100ml water at 20 °C.

• It is also soluble in alcohol, glycerol, etc. 

• It is highly soluble in methanol. For example, at 66.1 °C temperature, 102.75 grams of lead acetate is soluble in 100 grams of methanol. 

• Its 20 grams are soluble in 100 g of glycerol at 15 °C.

• It has a monoclinic crystal structure. 

• It is a non – flammable but toxic compound. On oral consumption, 400 mg/kg of it can be lethal for mice. 

• It is basic. 

• Its standard enthalpy of formation is -960.9 kJ.mol-1.

• Reaction with hydrogen sulfide – It reacts with hydrogen sulfide and forms lead sulfide and acetic acid. The reaction is given below –

Pb(C2H3O2)2 + H2S → PbS + 2CH3COOH

K2CrO4 + Pb(C2H3O2)2 → PbCrO4 + 2CH3COOK

 

Production of Lead Acetate 

It can be produced by following two methods –

• By the reaction of acetic acid, hydrogen peroxide, and elemental lead

• By the reaction of copper acetate and lead metal

By the reaction of acetic acid, hydrogen peroxide, and elemental lead – Elemental lead is boiled in acetic acid and hydrogen peroxide which results in lead acetate and water. Lead carbonate or lead oxide can be used in place of elemental lead. The reaction is given below –

 

Pb(s) + H2O2(aq) + 2H+_(aq)→ Pb2+(aq) + 2H2O(l)

 

Pb2+(aq) + 2CH3COO−(aq) → Pb(CH3COO)2(aq)

 

By the reaction of copper acetate and lead metal – Lead metal on reaction with copper acetate displaces copper metal and forms lead acetate by a single displacement reaction. The equation is given below –

 

Cu(CH3COO)2 + Pb → Cu + Pb(CH3COO)2

 

Uses of Lead Acetate 

Lead acetate was used as a sweetener due to its slightly sweet taste. Ancient Romans used to boil grape juice in lead pots to produce reduced sugar syrup. This sugar syrup was called defrutum. But after a few years, it was recognized that lead compounds (or lead acetate) are toxic and were causing lead poisoning in those who were consuming the sugar syrup. Currently, its usage as a sweetener is banned. 

 

Lead acetate has been widely used in the cosmetic industry for a long time but due to its toxicity, presently its use has been limited. Nowadays it is mainly used in the production of hair coloring products. Although in many places such as Canada, European Union, and California lead acetate is completely banned in food items and cosmetic products as well due to its carcinogenicity and reproductive toxicity. It was also used as a remedy for sore nipples. 

 

Lead acetate solution which is also known as Goulard’s Extract is used as an astringent to constrict mucous membrane and exposed tissues in modern medicine. Specifically, Goulard’s extract is a solution of lead acetate and lead oxide which was first introduced by French surgeon Thomas Goulard. 

 

A paper made up of lead acetate is used in the detection of poisonous gas H2S. Moist lead acetate on reaction with hydrogen sulfide gas gives lead sulfide. 

 

It is also used in the cleaning and maintenance of stainless steel suppressors and compensators. It was also used in making matchsticks during the Medieval period. Sugar of lead is used in boiled linseed oil to increase its effectiveness. 

 

Lead(II) Acetate: Summary in Tabular Form 

 

Conclusion:

This ends our coverage on the topic “lead acetate”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic.

 

The formula of Lead Acetate:

Lead acetate is a white crystalline compound with a chemical formula Pb(C2H3O2)2.

 

Structure of Lead Acetate:

 

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Properties of Lead Acetate:

 

Production of Lead Acetate:

Lead acetate can be made by boiling elemental lead in acetic acid and hydrogen peroxide. This method will also work with lead carbonate or lead oxide.

 

Pb_(s) + H2O2_(aq) + 2 H+_(aq) → Pb2+_(aq) + 2 H2O_(l)

 

Pb2+_(aq) + 2 CH3COO−_(aq) → Pb(CH3COO)2_(aq)

 

Lead(II) acetate can also be made via a single displacement reaction between copper acetate and lead metal:

 

Cu(CH3COO)2 + Pb → Cu + Pb(CH3COO)2

 

Uses of Lead Acetate:

Sweetener: Similar to other lead (II) salts. Lead acetate (II)  has a sweet taste and has historically been used as a sugar substitute for wine and food. The ancient Romans, who had few sweeteners other than honey, boiled must (grape juice) in a reed pot to make a sugar-reduced syrup called syrup, which was concentrated and returned to Sapa. This syrup was used to sweeten wine and  sweeten and preserve fruits. Lead (II) acetate or other lead compounds in the syrup may have caused lead poisoning in those who ingested it. Lead acetate has been shown to be toxic and is no longer used in the production of sweeteners. 

Modern chemistry can easily see it and has almost completely stopped its illegal use, which has continued for decades since its use as a sweetener was banned. Cosmetics: Lead acetate (II) and white lead have been used in cosmetics throughout history.  Medical Use: Lead (II) Acetate Solution is a common folk remedy for nipple pain. In modern medicine,  it was sometimes used as an astringent, in the form of a gall extract, and  also  to treat poison ivy.  Industrial Use: Lead (II) acetate paper is used to detect the toxic gas hydrogen sulfide. The gas reacts with lead (II) acetate on  moistened test strips to form a gray precipitate of lead (II) sulfide.

Liquefied Natural Gas (LNG) is generally methane or natural gas that has been liquified to make storage and LNG transportation easy. It is almost six hundred times smaller than natural gas in itself when the latter is in the gaseous form, making it easy to be shipped overseas. LNG is produced when natural gas is cooled below its boiling point, that is, -162°C or -258°F. And then, it is stored in containers that are double-walled cryogenic or are slightly above what we call atmospheric pressure. It is very easy to convert it back to the gaseous state, and this can be done by just raising its temperature. This is the LNG liquefaction process that takes place in LNG plants.

Usage and Transportation

LNG is far more practical as compared to Liquified Petroleum Gas (LPG), or other liquid gases that there are, especially when it comes to usage in large volume since it has the very same composition that natural gas does! This fact, along with the steadily growing demand for natural gas, has caused a stimulation for LNG production. What’s more, LNG technology makes it very possible to use natural gas from those remote parts of the world where there was previously no commercial use, and it was, in fact, being burned or flared as it is called.

There are special tankers called the LNG carriers that have supercooled cryogenic tanks that transport this liquified gas from countries like Algeria, Indonesia, Australia, and Qatar to the markets that are in Japan, Surprise, and China. At the beginning of the 21st century, there was an expansion of the natural gas pipelines in the United States, and this resulted in the nation being the net exporter of LNG, where it previously was just the vital importer of this gas.

Liquefied Natural Gas is generally reverted back to its gaseous state or is regasified as it is called, at the import terminals that are in the recipient counties. It is then injected into the natural gas pipelines and then, in this way, is transported to power plants and other distribution companies for the various industrial needs that there are. 

How is LNG Made?

As mentioned above, liquified gas is primarily methane and is made when the temperature of natural gas is brought down to -258°F. What happens during this cooling process is that the other components of natural gas like the other hydrocarbons, sulfur compounds, oxygen, nitrogen, carbon dioxide, and water and gradually but steadily removed, leaving behind almost pure methane. This is an essential process as many of the compounds that get removed during the process of liquefaction can potentially damage the downstream facilities that there are. Another risk is that some compounds could freeze instead of liquefying as is needed.

LNG is considerably denser when compared to gaseous natural gas; however, when it comes to volume, it is much lighter than water. It actually weighs less than half of the weight of water, and if it were to be spilled on water, it would actually float. The energy-dense yet lightweight nature of the gas makes it easy to transport. This is done in large tankers that are ocean-going that have double hulls to ensure extra insulation to help keep the LNG cold as it should remain. The process of refining natural gas and LNG liquefaction happens in an LNG plant.

It is also important to talk about floating liquefied natural gas facilities. Floating liquefied natural gas facilities are, as the name suggests, flotation production storages. They also function as offloading units that conduct LNG operations for those natural gas resources that are offshore and developing.

Advantages and LNG Uses

As mentioned, natural gas liquefaction results in Liquefied Natural Gas, which is very easy to transport. This makes it possible for isolated natural gas deposits like pipelines to have the gas recovered and also transported with the use of tankers. These tankers are very safe, and it is estimated that they have sailed over a hundred million miles with no death or major shipboard accident even though some land-based, on-site accidents have taken place.

However, LNG is neither explosive nor flammable like a liquid is. When it starts vaporizing, it may potentially be flammable or explosive but only in the range of 5-15% of natural gas in the air. When it is at less than 5%, there isn’t enough natural gas to burn, and above 15%, there’s not enough oxygen for it to burn.

LNG also allows convenient storage even in off-peak times. This can be referred to as ‘peak-shaving,’ and it is about the storage of the natural gas that is a surplus, in LNG form in those periods where energy consumption is lower. When the demands for energy rise, it can be regasified and then be used to meet the higher levels of demand, thereby preventing energy shortage.

LNG uses are vast and many, and to sum it all up, we can say that it is a source of energy. When LNG gets regasified to its original state, it can be used across industrial, commercial, and residential sectors for things like generating electricity, cooking, heating, and also for the manufacture of a rather large variety of products. It is also used as fuel for vehicles that are heavy-duty and also otherwise. 

The earth has provided tons of resources for human advancements. The layers of earth are abundantly rich with minerals and resources. These minerals are extracted from the crust of the earth surface and utilised in different manners. Moreover, these elements have turned out to be purposeful in several distinctive fields ranging from healthcare to the industrial sectors. One of the most useful minerals out of these is magnesium. This mineral is utilised in different spheres. Moreover, it has paved the ways for further discoveries in vast sectors.

Magnesium is one of the most chemically active elements found in the periodic table. It is a part of the metal family. It was used for thousands of years but in a clustered form. In the past few decades, scientists have figured out the isolation process of the element ‘magnesium’ and its effective applications. It was the chemist, Sir Humphry Davy who first carried out the purification and isolation of magnesium metal. This experiment was carried out in the year 1808. The metal was first discovered by a scientist named Joseph Black.

Magnesium is donated by the symbol of Mg, and an atomic number of magnesium is 12 in the periodic table. Moreover, the metal possesses abilities to act as a reducing agent under certain conditions. This often results in the formation of essential metal oxides.

The earth’s crust consists of a total of 2 percent of magnesium element. Moreover, it is among the top ten most abundant metals found in the earth layers. Also, it is the most abundant metal present in the seawater. The presence of magnesium can be witnessed in areas like salt layers and brines also.

Since the past few years, magnesium has resulted in several discoveries. It has provided multiple possible applications as well. As a result, it is one of the most versatile metals ever discovered in the field of science and chemistry.

Properties of Magnesium

• Magnesium element is considered one of the principal elements in the periodic table. With atomic weight as 24.305, it is a member of the alkaline-earth metal family. It occurs in the form of complex compounds like Epsom salt, magnesia, magnesites, oxides, hydroxides, etc.

• Magnesium metal is the eighth-most abundantly found element in the earth’s crust. However, it is produced by the electrolysis of molten magnesium chloride, commercially. This compound is obtained from the seawater.

• The metal is silvery-white in appearance and easily ignites in the presence of air. It is lightweight but strong in composition. However, the element holds a density of 1.738 g/mL; this indicates that though it is lightweight but can subsequently sink in water. The surface of the Mg is covered by a thin layer of oxides. This oxide ensures that the metal surface is well protected from the air particles.

• The Mg element also produces a bright white flame when it is ignited in the presence of air. The metals also showcase high reactivity probability towards halogen elements like bromine, chlorine, etc. and form magnesium compounds.

Uses of Magnesium

Magnesium is used for carrying out diverse applications. Due to its abundance in nature, it is easily extracted and put to different uses. However, the isolation process of magnesium requires long time durations. As a result, it is mostly utilised in compound forms. Some of the most common applications of magnesium are-

• It is used in the production of products which are required to be lightweight. These products are laptops, luggage bags, car seats, power tools, etc.

• The metal is utilised in the making of fireworks, sparklers, and flares. This is because it ignites easily in the presence of air. Moreover, it showcases a bright light while burning.

• In human bodies also, it is an essential mineral. Magnesium is required to help in the working of multiple enzymes. Also, it is vital for human bones.  

Alcohols are saturated organic compounds that contain at least one hydroxyl group (OH). The general formula of alcohol is CnH2n+1OH. Alcohol can be of many types. In this article, we will discuss the mannitol. This article will cover all important points like what is mannitol, mannitol structure, mannitol uses, mannitol action and mannitol injection uses. 

What is Mannitol?

Mannitol is a six-carbon, linear, simple, and polyhydroxy sugar alcohol. It is a low molecular weight compound. Its chemical formula is C6H14O6.  It gets easily filtered through the glomerulus but it can not be reabsorbed in the renal tubule of the kidney. 

Mannitol Structure

Mannitol is an isomer of sorbitol. The only difference in the structure of mannitol from sorbitol is the orientation of the hydroxyl group on the second carbon. All the carbons present in the mannitol are sp3 hybridized. All bonds present in the mannitol are sigma bonds.

Comparison of Sorbitol and Mannitol.

Properties of Mannitol

• The molar mass of mannitol is 182.172 g/mol.

• The density of mannitol is 1.489 at 68°F.

• The boiling point of mannitol is 563°F at 3.5 mm Hg.

• The melting point of mannitol is 333°F. 

• It is an odourless compound.

• It occurs naturally in white crystalline or in granule form.

• It is sweet in taste.

Mannitol Action 

• Mannitol is a polyhydroxy compound, which is mildly metabolized by the body. The renal tubule does not have the capacity to absorb it. Therefore, it rapidly gets excreted by the kidney, when mannitol injection is used and poorly absorbed when taken orally.  

• Mannitol, when ingested orally, passes through the intestine and excreted in the feces as the small intestine is not able to absorb it properly. Therefore, it does not affect blood sugar and can be used as a sweetener for the diabetic patient.

Mannitol Uses

• Mannitol is used for promoting diuresis for acute renal failure.

• Mannitol is used for increased intracranial pressure.

• Mannitol is used for the excretion of toxic material.

• Mannitol is used as a sweetener for diabetic food products.

• Mannitol is used for preventing intradialytic hypotension.

• It is used to measure Extracellular Fluid (ECF) and Glomerular Filtration Rate (GFR).

• It is used in cardiopulmonary bypass.

Mannitol Injection Uses

Mannitol is used as a medicine. Mannitol infused into a vein or into the urethra. It should never be given subcutaneously. It is infused by health care professionals in a hospital or clinic. The total concentration, dosage, and rate of mannitol administration should be governed by the nature and severity of the condition. The standard adult dose ranges from 50-200 g/day. The rate of infusion is usually adjusted to maintain a urine flow. 

Harmful Effects of Mannitol

• It can cause dehydration when consumed in excess amounts.

• At low temperature, it gets precipitated and can damage the vascular organ system.

• It can cause heart failure.

• It can cause pulmonary edema.

• It can cause renal failure.

Did You Know?

• Mannitol is found in mushrooms, brown algae, and bark of manna trees.  

• Mannitol lowers the blood pressure. 

• Mannitol in the intestine for a long time can cause bloating and diarrhoea.  

Transition metals are actually the various chemical elements that have valence electrons. It means electrons that can promote the formation of chemical bonds in two shells instead of just one. Although the term transformation does not have any specific chemical meaning, it is a convenient name for distinguishing the similarity of the atomic structures and the resulting properties of the elements. They occupy the center portions of the periodic table of elements between the groups on the left and the groups on the right. Specifically, groups 3 (IIIb) through 12 (IIb)

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What is a Metallic Character? 

According to the metallic character definition, Metallic character refers to the level of the metal’s reactivity. Metals tend to lose electrons in chemical reactions, as implied by their low ionization energy. Metal atoms have a low attraction for electrons within the compound, as indicated by their low electronegativity.

Physical properties related to metallic character involve metallic luster, glossy appearance, high density, high electrical conductivity, and high thermal conductivity. Most of the metals with metallic characters are malleable and ductile and can be deformed without breaking. In this case, Zn, Cd, Hg, and Mn are exceptions. The rest of the elements show one or more metallic characters at room temperature. Except for the metals which are exceptions, the remaining of the elements are hard and have low volatility.

Metallic Character Trend 

According to the modern periodic table, the metallic character of an element decreases as we move from left to right in the periodic table. This is due to the fact that, while moving from left to right in a period of time, the number of electrons and protons in an atom is expected to increase, which makes the nuclear force stronger, and therefore it becomes more difficult to lose electrons.

Metallic character increases down the group. This kind of metallic character trend happens because the atomic radius increases while moving down the group, which makes it easier to lose electrons.

How to Recognize Elements with Metallic Trends?

• Metallic characters are shown by metals, all of which are on the left side of the periodic table.

• The only exception is hydrogen, which is a non-metal under normal conditions. Yet hydrogen behaves like metal when it’s liquid or solid, but perhaps you should perceive it non-metallic for most purposes.

• Metallic elements occur in certain groups or columns of elements, including alkali metals, alkaline earth metals, transition metals (including lanthanide and actinides below the main body of the periodic table), and base metals.

• Other metal categories encompass base metals, noble metals, ferrous metals, heavy metals, and precious metals. Metalloids display some metallic character. However, this family of elements also has some non-metallic properties.

What are Transition Metals?

The metals in the periodic table that mostly consist of the d-block transition elements possessing unique and useful properties are known as transition metals. There are a total of 56 transition elements present in the periodic table which are further classified into three main groups-

There are incomplete inner electron shells in the case of transition metals which act as the transitional links between the most electropositive and least electropositive between the series of elements. The characterization of the transition metals can be done by the points listed below-

Transition Metals – Metallic Character

Transition metals possess low ionization energies and several vacant orbitals are present in their outermost shell. This is the reason behind their metallic character. Typical metallic properties are exhibited by transition metals because of the formation of metallic bonds between them. The presence of covalent bonds is indicated by the hardness that these metals possess which is because they have unpaired d-electrons. The unpaired electrons which are present in the d-orbitals may overlap leading to the formation of covalent bonds.

 

The number of covalent bonds present depends on the number of unpaired electrons. If the number of unpaired electrons is high, the covalent bonds will be formed more. This property leads to an increase in the hardness and strength of the metal. 

The transition metals including chromium, molybdenum, and tungsten are known to be very hard metals because they have the maximum number of electrons present in their d-orbital while on the other hand metals like mercury, zinc, and cadmium are not at all hard since no unpaired electrons are present in their d-orbitals. 

The metallic depends upon the easiness of a metal with which it loses electrons. When we move left to right across the periodic table, there is an increase in the number of protons and electrons which further leads to an increase in nuclear forces on the electrons which makes it difficult for them to lose electrons, therefore the metallic character while moving left to right decreases. As the atomic radius is increased there is an increase in the metallic character as well. Therefore while moving top to bottom, the metallic character of the elements is increased. 

Explanation for the Metallic Character of Transition Elements

• Transitional elements have a metallic character because they have low ionization energies as well as several empty orbitals in their outer shells. Such a property leads to the formation of metallic bonds in transition metals and hence demonstrates common metallic properties.

• These metals are hard, indicating the presence of covalent bonds. This is due to the presence of unpaired d-electrons in transition metals. The d-orbital containing unpaired electrons can sometimes overlap and establish covalent bonds. The higher the number of unpaired electrons present in the transition metals, the greater the number of covalent bonds formed by them.

• The chromium (Cr), tungsten (W) and molybdenum (Mo) metals have a maximum number of unpaired d-electrons. These transition metals are therefore exceedingly difficult. On the other hand, zinc (Zn), cadmium (Cd), and mercury ( Hg) are not extremely hard because they do not have unpaired d-electrons.

Metallic character with Alloys 

Although the metallic character is mainly related to pure elements, alloys could also have a metallic character. For example, bronze and most copper, magnesium, aluminum, and titanium alloys usually show a high level of metallicity. A few other metallic alloys consist purely of metals, but most often contain metalloids and nonmetals, while retaining the properties of metals.

Example Questions 

1. Give some examples of metals that display metallic character 

The metals that display with metallic characters are francium, caesium, sodium, copper, silver, iron, gold, aluminum, etc. Caesium and francium are the elements that display the highest metallic character.

 

2. How does the atomic radius vary in the metallic trends of transition elements? 

The atomic radius increases by going down a group, by moving the outer electrons further away from the nucleus. It makes the electron less attracted to the nucleus. As a result, metals become more reactive as we go down the group.