ATOMS, MOLECULES AND NUCLEAR CHEMISTRYATOMS AND MOLECULES
The combination of different elements to form compounds is governed by some basic rules. These rules, collectively called ‘laws of chemical combination’.
LAW OF CHEMICAL COMBINATIONS
Law of Conservation Mass:
Lavoisier, who is widely regarded as the father of modem chemistry gave the law of conservation of mass. This law states that in any chemical reaction, the mass of the substances that react equals the mass of the products that are formed.
Law of Definite Proportions:
This Jaw was given by Joseph Proust, a French chemist, in 1799. Proust’s law of definite proportions states that different samples of the same compound always contain its constituent elements in the same proportion by mass.
Law of Multiple Proportions:
In 1803 Dalton gave this law. As per this law if two elements combine to form more compounds, the masses of one element combine with a fixed mass of the other element, are in the ratio of small whole numbers.
The Law of Gaseous Volume:
When gases react, the volumes consumed and produced, measured at the same temperature and pressure, are in ratios of small whole numbers. This is also known as Gay-Lussac’s Law.
Dalton’s Atomic Theory
The hypotheses about the nature of matter on which Dalton’s atomic theory is based can be summarized as:
Matter consists of indivisible atoms.
All the atoms of a given chemical element are identical in mass and in all other properties.
Different chemical elements have different kinds of atoms and in particular such atoms have different masses.
Atoms are indestructible and retain their identity in chemical reactions.
Laws of Chemical Combination and Dalton’s Theory
Dalton’s fourth postulate explains the law of conservation of mass.
The fifth postulate is an attempt to explain the law of definite proportions.
ATOMS
Atoms are building blocks of all matter. On the basis of Dalton’s atomic theory, we can define an atom as the basic unit of an element that can enter into chemical combination. The size of an atom is extremely small and not visible to eye. The comparative idea regarding the size of atom can be had from the following:
ELEMENTS CLASSIFICATION AND CHEMICAL BONDINGCLASSIFICATION OF ELEMENTS
Four major attempts made for classification of the elements are follows:
Dobereiner’s Triads
Newlands’ Law of Octaves
Mendeleev’s Periodic Law & Periodic Tables
Modern Periodic Table
Dobereiner’s Triads
In 1829, J.W. Dobereiner, a German chemist made groups of three dements each and called them triads.
All three elements of a triad were similar in their physical and chemical properties. He proposed a law known as Dobereiner’s law of triads,
According to this law, when elements are arranged in order of increasing atomic mass, the atomic mass of the middle element was nearly equal to the arithmetic mean of the other two and its properties were intermediate between those of the other two.
Newlands’ Law of Octaves
John Alexander Reina Newlands in 1863-64 noted that every eighth element showed similar physical and chemical properties, when the elements are placed in the increasing order of their atomic masses. This was called the Newlands law of octaves.
The law states that when elements are placed in the increasing order of atomic masses, the properties of the eighth elements are repeated.
Mendeleev’s Periodic Law and Periodic Table
On arranging the elements in the increasing order of atomic masses, it was observed that the elements with similar properties repeat periodically.
In 1869, Mendeleev stated his observation in the form of the following statement winch is known as the Mendeleev’s Periodic Law
The chemical and physical properties of elements are periodic function of their atomic masses.
Mendeleev arranged the elements in the form of a table which is known as the Mendeleev’s Periodic Table as below:
Elements were arranged in increasing order of their atomic masses in horizontal rows till element whose properties were similar to those of the first element was came across.
Salient Features of Mendeleev’s Periodic Table
The following are the main features of this periodic table:
The elements are arranged in rows and columns in the periodic table.
The horizontal rows are called periods. There are six periods in the periodic table. These are numbered from 1 to 6 (Arabic numerals). Each one of the 4th, 5th and 6th periods have two series of elements.
All the elements present in a particular group are chemically similar in nature. They also show a regular gradation in their physical and chemical properties from top to bottom.
Modern Periodic Law and Periodic Table
The Modern Periodic Law states that the chemical and physical properties of elements are periodic functions of their atomic numbers, i.e. if elements are arranged in the order of their increasing atomic number, the elements with similar properties are repeated more...
NON - METALS
Non-metals occupy the upper right hand comer of the periodic table.
Seventeen elements are generally classified as non-metals. Their names as per their states in the normal conditions are:
Gases: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon.
Liquid: bromine.
Solid: carbon, phosphorus, sulphur, selenium, and iodine.
PROPERTIES OF NON-METALS
Physical Properties
Non-metals are neither malleable nor ductile.
They are brittle (break easily).
They do not conduct heat and electricity.
They are not lustrous (not shiny). They are dull.
They are generally soft (except diamond which is extremely hard non-metal).
They may be solid, liquid or gases at the room temperature.
They have comparatively low melting points and boiling points (except diamond which is a non-metal having a high melting point and boiling point).
Non-metals have low densities, that is, non-metals are light substances.
Non-metals are non-'sonorous. They do not produce sound when hit with an object.
Chemical Properties of Non-Metals
Non-metals are more reactive with metals than with other non-metals. Generally non-metals react with each other at a high temperature.
Action of Air:
Non-metals do not react with air at room temperature except white phosphorus.
Action of water:
Generally, non-metals do not react with water. However, chlorine dissolves in water and form an acidic solution.
Displacement of one non-metal by another from salt solution:
Just like metals, non-metals also differ in their reactivity’s. Among halogen family (i.e. Cl, Br, I and F) the most reactive is chlorine (Cl). The order of reactivity is Cl > Br > I. Thus chlorine can displace Br and I from solutions of bromides (NaBr) and Iodides (Nal).
Reaction with metals:
Non-metals with high electronegativity (F, Cl, Br etc.) generally reacts with alkali and alkaline earth metals to form ionic compounds.
Handy Facts
Allotropes are different from of the same element. Different bonding arrangements between atoms result in different structures with different chemical and physical properties. For example: The all tropes forms of carbon are white, red and black phosphorous. The term allotropy is referred to element only another term polymorphism is used to mean the ability of solid to exist in more than one term or crystal structure.
SOME IMPORTANT NON-METALLIC ELEMENTS
Hydrogen
The discovery of hydrogen is credited to Henry Cavendish in 1766, although it had been isolated as early as 1671 by Robert Boyle.
Isotopes of Hydrogen
Three isotopes of hydrogen exist and all occur naturally.
\[^{\text{1}}\text{H}\]is sometimes called Protium, It is abundent in nature. It is the only hydrogen isotope lacking neutrons.
The second isotope, \[^{2}\text{H}\], is called deuterium
Handy Facts
D-element bonds are more difficult to break than H-element bonds and this fact allows the mechanisms or many chemical reactions to be examined. \[{{D}_{2}}O\]itself is important as a material that slows neutrons in nuclear reactors.
The third isotope,\[^{3}\text{H}\], Tritium is radioactive.
ORGANIC CHEMISTRYOrganic chemistry is the study of carbon containing compounds and their properties. This includes the great majority of chemical compounds on the planet, but some substances such as carbonates and oxides of carbon are considered to be inorganic substances even though they contain carbon. There exists a large number of organic compounds.Differences between Organic and Inorganic CompoundsFollowing table compares the properties of the organic and in organic compounds:
Organic Compounds
Inorganic Compounds
Use mostly covalent bonding
Mostly ionic bonding
Are gases, liquids or solids with low melting points
Are generally solids with high melting points
Mostly insoluble in water
Many are water soluble
Many are soluble in organic solvents such as petroleum, benzene and hexane
Most are not soluble in organic solvents
Solution in water generally do not conduct electricity
When dissolved in water con- ducts electrical current
Living systems are made of a number of complex organic compounds which are called bio-molecules. The various biomolecules are carbohydrates, amino acids, proteins, enzymes, lipids, hormones; etc. We may call these molecules of life also.
SOME IMPORTANT MOLECULES OF LIFE
Carbohydrate
The chemicals used by the body may be divided into two categories;
Macronutrients: those substances that we need to eat regularly in fairly large quantities.
Micronutrients: those substances that we need only in small quantities.
Carbohydrates are the main energy sources for the human body. Chemically, carbohydrates are organic molecules in which carbon, hydrogen, and oxygen bond together in the ratio:\[{{C}_{X}}{{({{H}_{2}}O)}_{Y}}\], where X and Y are whole numbers.
Animals obtain carbohydrates by eating foods like potatoes, rice, breads, and so on. These carbohydrates are manufactured by plants during the process of photosynthesis. Plants harvest energy from sunlight to run the reaction just described in reverse:
\[6C{{O}_{2}}+6{{H}_{2}}O+energy\,(from\,\,sunlight)\xrightarrow[{}]{{}}{{C}_{6}}{{H}_{12}}{{O}_{6}}+6{{O}_{2}}\]
There are two types of carbohydrates, the simple sugars and those that are made of long chains of sugars - the complex carbohydrates.
Simple Sugars
All carbohydrates are made up of units of sugar (also called saccharide units). Carbohydrates that contain only one sugar unit (mono saccharides) or two sugar units (disaccharides) are referred to as simple sugars. Simple sugars are sweet in taste and are broken down quickly in the body to release energy. Two of the most common mono saccharides are glucose and fructose. Glucose is the primary form of sugar stored in the human body for energy. Fructose is the main sugar found in most fruits. Both glucose and fructose have the same chemical formula (\[{{C}_{6}}{{H}_{12}}{{O}_{6}}\]); however, they have different structures. Disaccharides have two sugar units bonded together. For example, common table sugar is sucrose, a disaccharide that consists of a glucose unit bonded to a fructose unit.
Sweetening power of common sugars:
Fructose> Invert sugar> Sucrose> Glucose> Maltose> Lactose
Complex Carbohydrates
Complex carbohydrates are polymers of the simple sugars. In other words, the complex carbohydrates are long chains of simple sugar units bonded together. Therefore the complex carbohydrates can also be referred to as polysaccharides. Starch is an example of complex carbohydrate.
Handy Facts
Both starch and glucogen are polymers of glucose; however, starch is a long, straight chain of glucose units, wheras glycogen is a branched chain of glucose units. Another important polysaccharide is cellulose. Cellulose is yet a third polymer of the monosaccharide glucose. Cellulose differs from starch and glycogen in terms of extra stability. Cellulose, also known as plant fibre, cannot be digested by human beings, therefore cellulose passes through the digested tract without being absorbed into the body. Cellulose fibre is essential in the diet because it helps exercise the digestive track and keep it clean and healthy.
AMINO ACIDS AND PROTEINS
Amino Acids
Amino acids play central roles both more...
BIOLOGICAL CLASSIFICATION/CELL & ITS DIVISIONBIOLOGICAL CLASSIFICATION
Biological classification is the scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing the groups in a hierarchy of categories. The purpose of biological classification is to organize the vast number of known plants and animals into groups that could be named, remembered and studied.
NEED FOR THE BIOLOGICAL CLASSIFICATION
Classification is needed to
help in establishing relationship between different organisms and to know about their evolution.
help in the identification of organisms.
study one or two organisms of one particular group and give the sufficient information of that group. It gives an idea of whole range of diversity found in organisms.
it gives an idea of the evolution of various groups of organisms.
Systematics
Systematics is the study of the units of biodiversity. It is the study of the diversification of organisms and their relationship among living things through time. It includes the following parts:
Identification: It is a process of finding the correct name and place of an organism in a system of classification.
Classification: It is the arrangement of an organism in a particular group on the basis of their similarities and dissimilarities.
Nomenclature: It is a system of providing proper and distinct name to one particular organism which helps in recognizing that organism.
Taxonomy: It is a science dealing with the description, identification, naming and classification of organism.
Classification of Organisms
It is the arrangement of organisms into taxonomic group according to their similarities and dissimilarties. System of classification is an attempt to organize different organisms into different categories that we can use to study.
Hierarchy in Classification
Hierarchy in classification involves many steps. Each step represents a rank or category. All categories or steps together constitute the taxonomic hierarchy.
Species
The smallest tax on is species. At the species level organisms look alike and are able to breed with one another.
Genus
The next largest taxon is genus. At the genus level, there is a group of similar species that are closely related.
Family
A group of two or more genera with common characteristics make a family. For example, lion (Panthera leo), tiger (Panthera tigris) and the domestic cat (Felis domesticus) make the family Felidae.
Order
A group of related families make an order. For example the family of cat (Felidae) and the family of dogs, foxes, etc. (Canidae) is grouped under the Carnivora.
Class
Related orders make a class. For example several orders like those of the tigers, cats, dogs, monkey, bats and human belong to class Mammalia.
Phylum
A phylum is the largest category with related classes grouped together. For example the classes of mammals, birds, reptiles, amphibians and fishes together constitute the phylum Chordata. more...
GENETICS AND BIOTECHNOLOGYGENETICS
Heredity is the transmission of genetic characters from parent to off springs. Individuals of same species have some differences, these are called variation.
MENDEL’S FINDINGS
Mendel’s Law of Dominance and Recessive
Each of the \[{{f}_{1}}\] generation plant shows inheritance of Y allele from one parent and a G allele from the other. When the \[{{f}_{1}}\] plants breed, each has equal chance of passing on either Y or G allele to each offspring.
In all the seven traits that Mendel examined, one form appeared dominant over the other i.e., it marked the presence of the other allele, e.g.
BASIC TERMS USED IN INHERITANCE STUDIES
· Allele: It is an alternative form of a gene which are located on same position (loci) on the homologous chromosome. Term allele was coined by Bateson.
· Homozygous: A zygote is formed by fusion of two gametes having identical factors is called homozygote and organism developed from this zygote is called homozygous.
Ex. TT, RR, tt.
· Heterozygous: A zygote is formed by fusion of two different types of gamete carrying different factors is called heterozygote (Tt, Rr) and individual developed from such zygote is called heterozygous.
· Hemizygous: If individual contains only one gene of a pair then individual is said to be hemizygous. Male individual is always hemizygous for sex linked gene.
· Phenotype: It is the external and morphological appearances of an organism for a particular character.
· Genotype: It is the genetic constitution or genetic make-up of an organism for a particular character.
· Back cross: A back cross is a cross in which \[{{F}_{1}}\]individuals are crossed with any of their parents.
· Test cross: When \[{{F}_{1}}\] progeny is crossed with recessive parent then it is called test cross.
· Monohybrid test cross: The progeny obtained from the monohybrid test cross are in equal proportion, means 50% is dominant phenotypes and 50% is recessive phenotypes.
It can be represented in symbolic forms as follows. \[{{F}_{1}}\]progeny (hybrid) \[\times \] Recessive parent
Monohybrid test cross ratio =1:1
· Dihybrid test cross: The progeny is obtained from dihybrid test cross are of four types and each of them is 25%.
Law of Segregation: According to this law, for any particular trait, the pair of alleles of each parent separate and only one allele passes from each parent to an off spring. Allele in a parent’s pair of allele is inherited as a matter of chance (we now know segregation of alleles occurs during the process of meiosis).
Law of Independent Assortment: This is also known as ‘Inheritance law’. According to this law, different pairs of alleles are passed to offspring independently of each more...
EVOLUTION AND ECOLOGICAL BIODIVERSITYEVOLUTION
The branch of life science for the study of ‘origin of life’ and evolution of different forms of life on earth was called bio evolution or evolutionary biology by Mayer, (1970). The word evolution means to unfold or unroll or to reveal hidden potentialities. Evolution simply means an orderly change from one condition to another. Evolution is slow but continuous process which never stop.
ORIGIN OF LIFE
Origin of life is the process by which living organisms developed from inanimate matter which is generally thought to have occurred on Earth between 3800 – 4200 millions years ago. First life evolved 3800-4200 million years back. There are several theories about the origin of life, like big bang theory, theory of special creation, theory of eternity, cosmozoic theory etc.
Chemosynthetic Theory of Origin of Life
The widely accepted theory is the Chemosynthetic theory of origin of life proposed by A.I. Oparin. It states that life has originated on earth through a series of combinations of chemical substances in the distant past. All these processes took place in water.
The early atmosphere contained ammonia (\[N{{H}_{3}}\]), water vapour (\[{{H}_{2}}O\]), hydrogen (\[{{H}_{2}}\]), methane
(\[C{{H}_{4}}\]). At that time there was no free oxygen.
Miller and Urey Experiment
CHEMICAL EVOLUTION AND ORGANIC EVOLUTION
Comparative Anatomy and Morphology
Different animals and plants show dissimilarities in their structure but in some characters they show similarity. These similarities provide one of the most concluding evidence of organic evolution.
Similarities are of two types: homology and
Let us discuss some of the important sources that provide evidences/or evolution.
Homologous organs: Homologous organs are similar in origin (or are embryo logically similar) but perform different functions.
For example, the forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar.
·
Analogous organs: Analogous organs have different origin but perform similar functions.
For example, the wings of a bird and a bat are similar in function but this similarity does not mean that these animals are more closely related.
Vestigial organs
The organs which are present in reduced form and do not perform any function in the body but correspond to the fully developed functional organs of related animals are called vestigial organs.
Human body possess about 180 vestigial organs. Some of these are - nictating membrane, muscles of pinna (auricular muscles), vermiform more...
TISSUE, PHYSIOLOGY OF PLANTS AND ANIMALSTISSUETissue is a group of cells with common origin, structure and function that work together to perform a particular function. For example. Blood, bone, cartilage are some examples of animal tissues while xylem, phloem, parenchyma etc. are different types of tissues found in plants. The study of tissue is called histology. The term was coined by Meyer.PLANT TISSUESOn the basis of their ability to divide, plant tissues are divided into two types:
Meristematic Tissues
Meristematic tissues are thin-walled compactly arranged, immature cells that keep on dividing continuously. The new cells produced are initially Meristematic. Slowly, they grow, differentiate and mature into permanent tissues.
The meristematic cells are spherical, or polygonal in shape and the cells are compactly arranged without inter-cellular spaces. The cell wall is thin, elastic and is made of cellulose. Each cell has abundant cytoplasm and prominent nuclei. These cells are always living.
Classification of meristematic tissue
On the basis of origin and development
Promeristem
Primary meristem
Secondary meristem
·Represents primary stages of rneristematic cells.
·present at the tip of radicle and plumule
·Originate from promeristem that continue to divide to form different tissues.
·Always in more...
Species
The smallest tax on is species. At the species level organisms look alike and are able to breed with one another.
Genus
The next largest taxon is genus. At the genus level, there is a group of similar species that are closely related.
Family
A group of two or more genera with common characteristics make a family. For example, lion (Panthera leo), tiger (Panthera tigris) and the domestic cat (Felis domesticus) make the family Felidae.
Order
A group of related families make an order. For example the family of cat (Felidae) and the family of dogs, foxes, etc. (Canidae) is grouped under the Carnivora.
Class
Related orders make a class. For example several orders like those of the tigers, cats, dogs, monkey, bats and human belong to class Mammalia.
Phylum
A phylum is the largest category with related classes grouped together. For example the classes of mammals, birds, reptiles, amphibians and fishes together constitute the phylum Chordata.
