Category: Chemistry Notes PPT

Carcinogen definition can be given as the substances, radionuclide, or the radiations, which are involved directly in the formation of cancer, are known as carcinogenic substances, otherwise, as a carcinogen, and this entire process is known to be carcinogenicity.

These carcinogenic substances can damage the genome or even disrupt the cells involved in the metabolism process. Various radioactive substances are considered carcinogenic, but these substances’ carcinogenic behavior is caused by the radiation they emit. Alpha particles and Gamma rays are the carcinogens examples or examples of carcinogenic substances. Also, we have non-radioactive carcinogens such as certain dioxins, tobacco smoke, and the inhaled asbestos. 

Note: Tobacco smoke produces harmful gases such as carbon monoxide, cancer-causing substances. Often, carcinogenic substances are thought of as synthetic chemicals or chemical carcinogens, but they can be synthetic and natural in reality. These substances need not be toxic immediately, as they are insidious.

Carcinogenic Substances

Cancer is a disease group that causes abnormal cell growth to spread to other parts of the human body. It is a disease where the body cells get damaged. In general, carcinogenic substances increase cancer risk because they damage the body’s metabolic cells. Also, they damage the cell’s DNA component, which is associated directly with various biological processes in the body, leading to tumors.

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Aflatoxin B1, which is produced by a fungus, grows on the surface of peanut butter, grains, and many nuts. It is also a microbial carcinogenic substance that occurs naturally. Also, the virus hepatitis B and human papilloma can cause cancer to the person infected by them.

Besides the virus, radiations, and fungus, there are various carcinogenic substances. The substances like polynuclear hydrocarbons and benzene, which have more than two benzene rings fused together, also contain carcinogenic effects. These polynuclear hydrocarbons form when incomplete combustion of organic material like coal, tobacco, and petroleum occurs. These substances undergo biochemical reactions by entering into the human body, which damages the DNA cells and causes cancer, further leading to death.

Toxicity is the degree to which a chemical can damage the body’s human cells. We have seen the carcinogenicity effect and the substances associated with it. These are highly toxic substances in nature, and their use should be avoided to sustain a healthy body.

What is Toxicity?

Toxicity is the degree to which a chemical substance or a specific mixture of substances can lead to damage to an organism. It can refer to the whole organism’s effect, such as an animal, plant, or bacterium, and the effect on the organism’s substructure, such as an organ or cell (cytotoxicity) like the liver (hepatotoxicity). 

As an extension, the word can be metaphorically used to describe the toxic effects on more complex groups, like the family unit or society. At times, the word is less or more synonymous with poisoning in daily usage.

The central concept of toxicology can be defined as the toxic effects are dose-dependent; even water can lead to intoxication when taken in higher doses. Even a very toxic substance like snake venom, there is a dose with no detectable toxic effect. 

Recently, a novel Drug Toxicity Index (DTI) has been proposed considering the limitations of this dose-response concept. DTI involves the responsibilities like, recognizes hepatotoxic drugs, redefines the drug toxicity, predicts clinical outcomes, gives proper mechanistic insights, and has the potential as a screening tool. Toxicity is species-specific, making the cross-species analysis problematic. 

On the other side, the newer metrics and paradigms are gradually developing to bypass animal testing while maintaining the concept or feature of toxicity endpoints.

Types of Toxicity

There are four types of toxic entities, as given below:

1. Chemical, 

2. Biological, 

3. Physical,

4. Radiation:

• Chemical toxicants are inorganic substances including mercury, chlorine gas, hydrofluoric acid, and organic compounds like most medications, methyl alcohol, lead, and toxins.

• The biological toxicity of pathogens is difficult to measure because the “threshold dose” can be a single organism. Theoretically, one virus, worm, or bacteria can reproduce to cause a serious infection.

• Physical toxicants exist due to their interference and physical nature with biological processes. Examples can be given as asbestos fibers, coal dust, or finely divided silicon dioxide, which can ultimately be fatal if inhaled.

• Radiation can hold a toxic effect on the organisms.

Classification of Toxicity

Let us look at the classification of Toxicity in detail.

For the substances to be handled and regulated appropriately, they must be classified and labeled properly. Approved calculations or testing measures determine the classification. It has determined the cut-off levels set by scientists and governments (threshold limit values, no-observed-adverse-effect levels, and tolerable daily intake levels).

The pesticides provide an example of well-established toxicity labels and class systems. While currently, most countries have various regulations concerning the test types, cut-off levels, numbers of tests, the Globally Harmonized System implementation has begun unifying these countries.

Cerium is a metal in grey and shimmering radiant. The symbol of Cerium is Ce in the periodic table and the atomic number is 58. It is one most abundant element of the rare earth elements and the 2nd most active lanthanide after europium and 25th most-abundant element with approx 0.0046% of Earth’s crust weight. It is soft but a little harder than lead. It is found in lanthanides. It contains 82 neutrons and  58 protons and 58 electrons. It is radioactive in nature as its number of neutrons is greater than the number of protons. 

Cerium is found in allanite, monazite, bastnaesite, and other minerals also. For commercial purposes, it is prepared by the reduction of the fused fluoride with calcium. 

Analytical techniques such as atomic absorption or emission spectrophotometry are used for the determination of cerium. Some of the other techniques are ICP-AES, stripping voltammetry, and involve high cost. 

Discovery of Cerium

Cerium has been discovered in the year 1803 by Jons Jacob Berzelius and Wilhelm Hisinger.  

Properties of Cerium

• Malleable – can be shaped accordingly by beating with a hammer or by the pressure.

• Ductile – can be drawn out into wire.

• Ignite – Burn if it is scratched with a sharp object.

• Moderately toxic.

• Highly reactive with bases, acids, hydrogen gas, and other metals.

• Oxidizes slowly in cold water and quickly in hot water. 

• It is slightly harder than lead and is iron-grey in colour.

• It is highly reactive and tarnishes readily in the air and it can dissolve in the acid.

• It oxidizes readily in the water ( slowly in cold water and rapidly in the hot water )

• It can be burned heated or scratched with a knife

CE Periodic Table 

What is Ce on the Periodic Table

 

Ionization Energies of Cerium 

1st Ionization energy / kJ mol-1 is 534.41

2nd Ionization energy / kJ mol-1: 1046.87

3rd Ionization energy / kJ mol-1: 1948.82

4th Ionization energy / kJ mol-1: 3546.608 

Cerium Uses

The world’s production of cerium is 23000 tonnes a year and is likely to increase in the future as the use of cerium is increasing day by day in our lives. The top 3 producers in the world are China, Russia, and Malaysia. Cerium is used commercially in industries as well as in household equipment.

• It is used in low-energy light bulbs

• It is used in cigarettes lighters

• It is used in colour screen TVs

• It is used in chromium plating

• It is used in nuclear reactor 

• It is used in Lasers

• It is used in microwave devices

• It is used in aluminium and iron alloys

• It is used in stainless steel as a hardening agent

• It is used gas mantles, in gas lighting

• It is used glass polishing agent

• It is used to clean up exhaust vehicles through the catalyst of catalytic converters 

• It is used in making pigments for containers, toys, household wares and crates

• It is used as the core of the carbon electrode in the arc lamp

• It also catalysis the reduction of the nitrogen oxide to nitrogen gas

• It is also used in the catalytic converter which consists of a ceramic or a metal substrate along with aluminium and is installed in every new car

Health Effects

Various health problems are caused by cerium. Nowadays more and more of the cerium is being used and using it in the working environment is almost dangerous because it is highly reactive in the air. The harmful damps and gasses can be inhaled with air through the respiratory system and if it accumulates in the human body, it can be a threat to the liver, lungs, especially during exposure for a long time and will also have a harmful effect if present for a short time also. It can also cause lung embolisms. It has also been noted that cerium stimulates salt metabolism and cerium also has no noted biological effect.

Environmental Effects

< p>Cerium is environmentally undesirable. It accumulates in soil and water and thus can lead to intense concentrations in humans, animals, and in soil particles. Cerium is dumped by petrol-producing industries. It is thrown away by households also in various equipment when cerium enters the equipment. Cerium causes damage to cell membranes in water animals that can affect reproduction and nervous systems badly and have several negative influences on reproduction.

On a positive note, cerium is used as a catalyst. Cerium is used in catalytic converters to improve the atmosphere wherever diesel engines operate. Ceramic filters burn the particulates and carbon particles emitted by diesel engines. It catalyses the burning of the particulate and eliminates them.

Little cerium oxide can be added to the fuel itself so that it can catalyse the burning of the particulates and abolish them.

An Introduction

One material can be transformed into another with differing qualities as a result of a chemical transformation. One or newer substances are likely to form in this environment. Synthesis or breakdown of two substances might lead to a new substance being formed as a result of this process. The oxidation reaction is one example of a chemical change that results in a chemical reaction. 

Chemical reactions are normally irreversible, except in the case of reversible alterations in chemistry. Some instances of chemical alterations are the creation of dye in the colour and the chemical change in the colour of hair.  

Chemical Changes 

It is possible for a chemical alteration to be reversed, or it is not. Let’s take a closer look at them.   

Reversible Change 

The term “reversible change” refers to a chemical alteration that can be undone. One or more approaches can be used to undo this alteration. Only the physical qualities of the material, such as its size and shape, tend to change in a reversible alteration. In the vast majority of circumstances, new material is not created when a chemical reaction is reversible. The elongation of a spring or the folding of paper are two examples of reversible chemical changes. 

Irreversible Change 

An irreversible change is a change that cannot be reversed by any physical or chemical methods. Newer substances are formed when a substance undergoes a permanent change. 

Reversible and irreversible alterations both have their merits and disadvantages. The blacksmith, for example, can cast a piece of iron into a variety of shapes. Following the heating procedure, the iron piece is pounded to the appropriate shape. Metals expand when heated and compress when cooled, as we know. In light of this, it is clear why we see reduced spaces between rails on the railway lines. In the summer, the temperature rises, causing the metal tracks to expand. Consequently, these gaps in the train lines compensate for the increase in the area. 

Chemical Process:  

  [Hydrogen(H_{2})+Oxygen(O_{2}) rightarrow Water(H_{2}O)] 

 

A chemical process is depicted in this diagram. hydrogen gas (2 H-H) is combined with oxygen gas (O=O) to form two molecules of water in the reaction (2 H-O-H). In the diagram, look at the arrow. What message does it convey? There is a strong correlation between the direction of the reaction and the formation of water.

Chemical symbols are abbreviations for chemical elements, functional groups, and compounds used in chemistry. Chemical element symbols are normally made up of one or two Latin letters, with the first letter capitalized.

An element is the purest version of a chemical in chemistry, containing only atoms and unable to be broken down further. These elements are classified and ordered in the contemporary periodic table based on their chemical and physical properties and atomic number (Z). Scientists and alchemists used a variety of esoteric symbols to depict chemical elements and compounds before chemistry was established as a separate subject of science. A chemist named John Dalton was the first to devise his own system of symbols for elements and compounds.

Berzelius is credited with inventing the typographical technique of representing elements with letters from their names or ancient names.

While the elements’ names were spelled differently in different languages, the symbols functioned to symbolize each of the chemical elements in the same way. Hundreds more chemical elements have been discovered as a result of advances in chemistry, and each of the 118 elements currently has its own distinct symbol.

A symbol represents the element’s stoichiometric quantity. The letter “B” stands for one atom of the element Boron, for example. Similarly, the letters “S” and “Mg” stand for one atom of Sulphur and one atom of Magnesium, respectively. There are 6.022 10-23 moles of particles in one atom. B has 6.022 10-23 moles of particles, which can be deduced.

The mass of an atom is known as atomic mass. In a balanced chemical process, a specific symbol represents the precise mass of a certain element. One nitrogen atom with an atomic mass of 14 u is represented by the letter N.

Compounds: In a complicated process, writing the compound’s whole chemical name takes a long time. Consider the chemical reaction represented in the diagram below. Is it easy to write H₂O or Water (formed product)? With symbols, of course!

Identity: Each of the 118 components is represented by a different symbol. There should be no ambiguity or misinterpretation while assigning or reading chemical symbols. For example, the first character in “Ca, Cu, C, Cr, Cs, Cl” is the same as “Ca, Cu, C, Cr, Cs, Cl,” but the second character is different. From left to right, the elements are calcium, copper, carbon, chromium, and cesium.

How can I Study Chemical Symbols the Most Effectively?

Make use of the Periodic Table to assist you. To build chemical formulas, become familiar with chemical symbols, which are most easily found on the periodic table of elements. The periodic table is a list of all known elements that include both the element’s full name and symbol, such as H for hydrogen and Cl for chlorine.

Cinnabar, which is also referred to as mercury sulfide (HgS), is the chief ore mineral of mercury. Commonly, cinnabar is encountered with marcasite, stibnite, and pyrite in veins near recent volcanic rocks and the deposits of hot-springs. The essential deposit is at Almadén – Spain, where it has been mined for over 2,000 years. The other deposits present in Huancavelica, Peru; Iudrio – Italy; and the Coast Ranges of California, the U.S. Metacinnabar, which is the isometric (cubic) form of cinnabar, that transforms to cinnabar upon heating at a temperature of 400°–550° C (750°–1,020° F).

More about Cinnabar

In general, cinnabar takes place as a vein-filling mineral associated with the alkaline hot springs and recent volcanic activity. This mineral resembles the quartz in symmetry and its exhibiting birefringence. Cinnabar mineral has a mean refractive index around 3.2, a hardness between 2.0 and 2.5, and a particular gravity of 8.1, nearly. The properties and colour derive from a structure, which is a hexagonal crystalline lattice that belongs to the trigonal crystal system, crystals that exhibit twinning sometimes.

Cinnabar mineral has been used for its colour since the antiquity in the Near-East, including as a cosmetic of rogue-type, in China since as early as the Yangshao culture, and in the New World since the Olmec culture, where it was used in colouring stoneware.

Associated with modern precautions for handling and use of cinnabar arise from the mercury component toxicity, which was recognized as early as ancient Rome.

Etymology

The term cinnabar derived from the Ancient Greek word, named kinnabari, most likely applied by the Theophrastus to many distinct substances. Whereas the other sources say, the term comes from the Persian word, named Arabicized, a word of uncertain origin. In Latin, it was known as minium, which also means “red cinnamon”, though both of these terms, which now refer particularly to lead tetroxide.

Properties and Structure

Properties

Commonly, Cinnabar is found in a massive, earthy, or granular form and is bright scarlet to brick-red in colour, even it occasionally takes place in crystals with a nonmetallic adamantine luster. In its symmetry, it resembles quartz. It exhibits birefringence, and it contains the second-highest refractive index of any mineral. Its mean refractive index is given as 3.08 (sodium light wavelengths), versus the indices for the non-mineral gallium(III) arsenide (GaAs) and diamond, which are 3.93 and 2.42, respectively. The hardness of cinnabar is given as 2.0–2.5 on the Mohs scale, and its specific gravity is 8.1.

Structure

Cinnabar structurally belongs to the trigonal crystal system. It occurs as a slender prismatic crystal or thick tabular or as granular to massive incrustations. Crystal twinning also occurs as simple contact twins.

It is to note that, HgS, mercury(II) sulfide, adopts the cinnabar structure and one additional structure, which means it is dimorphous. Cinnabar is more stable and is a structure akin to that of HgO: every Hg centre contain two short Hg−S bonds (each of 2.36 Å), and four longer Hg···S contacts (with 3.10, 3.10, 3.30, 3.30 Å separations). Additionally, HgS can be found in a black, which is a non-cinnabar polymorph (otherwise metacinnabar) that has the structure of zincblende.

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Occurrence

In general, cinnabar occurs as a vein-filling mineral associated with alkaline hot springs and recent volcanic activity. It is deposited by the epithermal ascending aqueous solutions (those near the surface and not much hot) far removed from the source of their igneous. It is also associated with stibnite, native mercury, pyrite, realgar, opal, marcasite, chalcedony, quartz, calcite, barite, and dolomite.

Mining and Mercury Extraction

Cinnabar has been mined as the common source of mercury in nature for thousands of years, even as far back as the Neolithic Age. It was mined both as a pigment and for its mercury content during the Roman Empire.

To produce liquid mercury (which is also called quicksilver), crushed cinnabar ore can be roasted in the rotary furnaces. And, pure mercury gets separated from the sulfur in this process and evaporates easily. A condensing column can be used to collect the liquid metal, which is often shipped in iron flasks.

Toxicity

Associated modern precautions for handling and use of cinnabar have arisen from the toxicity of the mercury component, which was recognized as early as in ancient Rome. Due to its mercury content, cinnabar might be toxic to human beings. Overexposure to mercurialism, mercury, was seen as an occupational disease to the ancient living Romans.

Other Forms of Cinnabar

• Paragite or hepatic cinnabar is the impure brownish variety from the Idrija mines in the Carniola region of Slovenia, where the cinnabar is mixed with earthy matter and bituminous.

• In the hexagonal crystal system, hypercinnabar crystallizes at high temperatures.

• Metacinnabar is a form of black-coloured mercury(II) sulfide, which crystallizes in the cubic crystal system.

What do you know about organic compounds? If we talk about in Chemistry terms, Organic compounds can be defined as any type of chemical compounds in which atoms of carbon, that could be one or more than one, are covalently linked to the other elements’ atoms. In very simple terms, you can say that organic compounds are simply any chemical compounds that have carbon, but it doesn’t mean that every carbon-containing compound can be known as organic, for e.g., cyanides, carbonates and carbides.

The best example of the simplest organic compound is Methane. A few examples of Organic compounds are cyclohexane, ethyne, ethane and ethane.

Classification of Organic Compounds

Organic Compounds can be classified on two bases. Firstly we will talk about organic compounds, which are based on “Structure,” and secondly, we will discuss the organic compounds, which are based on “Function.” Now we will study these classifications of organic compounds in detail.

1. Classification based on the structure

Let us look at the classification of organic compounds based on structure.

1. Acyclic or open chain compounds

2. Cyclic or closed chain compounds

1. Acyclic or Open-chain Compounds

Acyclic compounds are just opposite to cyclic compounds because their molecules don’t form any ring. It is called open-chain compounds because they have a linear structure. The best examples of these compounds are acyclic aliphatic compounds and alkanes. Open-chain compounds can be understood by straight-chain compounds and branched-chain compounds. The straight-chain compounds don’t have any side chains, but branched-chain compounds’ atoms have the straight chain and one or more than one side chain are attached to it.

2. Cyclic or Closed-chain Compounds

Cyclic compounds are also known as “Ring compounds.” As its second name suggests, cyclic compounds are those kinds of compounds where one or more than one number of atoms get connected to form a closed ring. It is not mandatory that every ring of these compounds is to be of the same size.

Cyclic or closed-chain compounds always have a prior place in human beings’ day-to-day life as humans encounter these compounds on a daily basis. They are also categorized into two divisions. The first division is about “Heterocyclic,” and the second division is about “Homocyclic.” Now we will discuss these categories one by one.

1. Heterocyclic compounds

Heterocyclic compounds are a kind of cyclic compound in which the ring structure exists. We can understand these compounds in a very simple definition as it is like any other dominant branch of organic compounds in which two or more two atoms join in the ring shape in their molecules. Although they have atoms of carbon, it must be noticed that at least one atom of another element also exists. The very familiar examples of these compounds are synthetic dyes, nucleic acids and most drugs.

2. Homocyclic compounds

If we talk about organic chemistry, Homocyclic compounds are the type of cyclic compounds, unlike heterocyclic, in which the ring structure is formed by the atoms. This ring structure is made up of the same elements’ atoms and this element is the carbon. These are called Carbocyclic compounds. No element other than carbon can exist in this compound. Although in inorganic chemistry, homocyclic compounds have ring structures that have been formed by diff-diff elements’ atoms like boron, sulphur, phosphorus and so on. The best examples of this compound are naphthalene, tetracene, benzene and so on.

Heterocyclic Compounds

Heterocyclic compounds are divided into two broad categories, which are named Alicyclic heterocyclic compounds and Aromatic heterocyclic compounds. Now, we will discuss these categories in brief.

Classification of Heterocyclic Compounds

1. Alicyclic Heterocyclic Compounds

We can understand these compounds by simple lines. Ring structures of these compounds have one or more than one heteroatom. We can understand these compounds by a few examples, which are tetrahydrothiophene, tetrahydrofuran and so on.

2. Aromatic Heterocyclic Compounds

These compounds can be easily defined by simple understanding. Unlike Alicyclic heterocyclic compounds, molecules of these compounds have one or more than one heteroatom. Examples of these compounds are thiophene, furan and so on.

Homocyclic or Carbocyclic Compounds

Homocyclic or carbocyclic compounds are basically divided into two compounds. The first compound is known as Alicyclic compound and the second is known as Aromatic compound. Now we will discuss these compounds in detail.

Classification of Homocyclic compounds

1. Alicyclic Compounds

The alicyclic compound is that kind of compound that is aliphatic and cyclic too. This compound has one or more than one all-carbon ring that can be saturated or unsaturated. The bonds which exist in pairs of atoms can be any type of bond like single, double or triple.

2. Aromatic Compounds

Aromatic compounds are those cyclic compounds that are unsaturated, unlike alicyclic compounds, which are either saturated or unsaturated. These compounds are also called aromatics or arenas. They are pleasant in the smell, as their Greek meaning suggests, which is “aroma.” These compounds can be distinguished by one or more than one planar ring of atoms linked by covalent bonds of two different types. A few examples of these compounds are benzene and toluene.

Classification of Aromatic Compounds

Aromatic compounds have distinctive stability and this is why they are referred to as aromaticity which is majorly concerned with odour. Now we will discuss the classification of these compounds, which are basically Benzenoid Aromatic Compounds and Non-Benzenoid Aromatic compounds. Further, we will discuss them in detail.

1. Benzenoid Aromatic Compounds

These aromatic compounds are mainly obtained from benzene. These compounds are distinguished by the existence of one or more than one isolated or fused benzene rings and their derivatives additionally in the structure. These compounds can be arranged as Monocyclic, Bicyclic and Tricyclic on the basis of the number of benzene rings which are fused together in the structure. In bicyclic and tricyclic compounds, there are two or more than two rings present in the structure. A few examples of these compounds are Phenanthrene, Naphthalene, Anthracene. In addition, a few of such compounds are represented below.

2. Non-benzenoid Aromatic Compounds

These aromatic compounds consist of other unsaturated rings instead of benzene rings. These aromatic compounds have special stability. Some examples of these compounds are Tropolone and Azulene.

2. Classification based on the functional groups

A functional group can be defined as a process in which a molecule receives its characteristic chemical properties from one or group of atoms that exist in the molecule. Now we must understand why we need to classify organic compounds on the basis of functional groups. The answer is very simple because it classifies the chemical behaviour of an organic compound. We need to understand that the nature of functional groups draws impacts on the reactions of compounds and at some level, their physical properties.

There are numerous organic reactions, which involve functional group transformation, and have no effect on the rest of the molecules. There are so many examples in the functional group case, such as the carboxylic acid group (-COOH), the hydroxyl group (-OH) and the aldehyde group (-CHO).