MUKHLiS TANVEER JAN KURD

Chemistry With Tanveer Kurd Behramshahi Mastung.

Chemistry - Oxygen

Introduction

Oxygen is the member of group 16 on the periodic table; however, most of the time, it is treated differently from its group.

The symbol of oxygen is ‘O’ and atomic number is ‘8.’

Oxygen

Oxygen has about nine allotropes and the most common allotrope is diatomic oxygen (i.e. O2). Other important allotrope is Ozone i.e. O3.

Oxygen, first time, was noticed by Swedish pharmacist Carl Wilhelm Scheele.

Salient Features of Oxygen

Oxygen is characteristically categorized as the member of “chalcogen” group.

The word "chalcogen" is derived from a Greek word “khalkόs,” which means “copper” and the Latin-Greek word “Genēs,” which means born or produced.

Oxygen is a highly reactive gas (or nonmetallic element); hence, it is an oxidizing agent that readily forms oxides with most of the elements and compounds.

Oxygen has six valence electrons.

The melting point of oxygen is -218.80C and the boiling point is -1830C.

Occurrence of Oxygen

With about 20.8 percent share (in total earth’s atmospheric constituents), oxygen is the second ranked element of the earth’s atmosphere.

Oxygen occurs almost in sphere of the earth namely atmosphere, hydrosphere, and lithosphere.

During the photosynthesis process, free oxygen is produced by all green plants.

Oxygen occurs as constituent copper ores.

A human body contains about 65 percent oxygen.

By mass, almost half of the earth’s crust is composed of oxygen (i.e. its oxides).

By mass, oxygen is the third-most abundant element that found in the universe; the first and second are hydrogen and helium accordingly.

Oxygen (i.e. O2) is a colorless and odorless diatomic gas.

Oxygen dissolves in water very easily; however, the solubility of oxygen in the water is temperature-dependent.

Compounds of Oxygen

Following are the major compounds of oxygen −

Oxide

Peroxide

Carbon dioxide - CO2

Hydroxide - OH-

Ozone - O3

Mercury (II) oxide - HgO

Chlorate - ClO3

Aluminum oxide - Al2O3

Carbon monoxide - CO

Hypochlorite - ClO-

Silicon dioxide - SiO2

Hypofluorous acid - HOF

Sodium peroxide - Na2O2

Potassium chlorate - KClO3

Oxygen difluoride - OF2

Sodium oxide - Na2O

Uses of Oxygen

Oxygen (O2) is the most essential requirements for the respiration, without it, life cannot be imagined.

Oxygen is used in medicine.

Oxygen therapy is typically used to treat some diseases, such as, emphysema, pneumonia, some heart disorders, etc.

Some of the underwater activities, such as scuba diving, submarines, etc. also use artificial oxygen.

Artificial Oxygen

Aircrafts, mountaineers, etc. also use artificial oxygen.

Oxygen is also used in some of the industries, e.g. smelting of iron ore into steel – in this process, about 55% of oxygen is used.

Chemistry - Nitrogen

Introduction

Nitrogen is a chemical element of group of 15 of the periodic table; among all the elements of group 15, it is the lightest element.

The symbol of nitrogen is ‘N’ and atomic number is 7.

Nitrogen

In 1772, Scottish physician Daniel Rutherford, first discovered and isolated carbon.

However, the name ‘nitrogen’ was first given by Jean-Antoine-Claude Chaptal in 1790.

Salient Features of Nitrogen

Nitrogen has two stable isotopes namely 14N and 15N.

Free nitrogen atoms normally easily react with most of the elements and form nitrides.

The molecules of N2 is colorless, odorless, tasteless, and diamagnetic gas at standard conditions.

The melting point of N2 is −2100C and the boiling point is −1960C.

Nitrogen compounds repetitively interchange between the atmosphere and living organisms, making a nitrogen cycle.

Occurrence of Nitrogen

Nitrogen is most abundantly found element on the earth, as it constitutes about 78.1% of the entire volume of the earth’s atmosphere.

Nitrogen gas, which is an industrial gas, largely produced by the fractional distillation of liquid air.

Compounds of Nitrogen

Following are the major compounds of Nitrogen −

Ammonium - NH4+

Ammonia - NH3

Nitric acid - HNO3

Nitrite - NO2-

Nitrogen dioxide - NO2

Dinitrogen pentroxide - N2O5

Hydrazine - N2H4

Dinitrogen - N2

Cyanide - CN

Ammonium nitrate - (NH4)(NO3)

Nitrogen trichloride - NCl3

Nitrogen trifluoride - NF3

Nitrogen triiodide - NI3

Pyridine - C5H5N

Nitronium ion - NO2+

Hydrazoic acid - HN3

Ammonium sulfate - (NH4)2SO4

Uses of Nitrogen

Nitrogen compounds are extensively used in wide range of fields and industries.

Pure nitrogen is used as food additive.

Used in fire suppression systems especially for the information technology equipment.

Also used in manufacturing stainless steel.

Nitrogen is also used to inflate the tires of some of the aircraft and race cars.

Liquid nitrogen is used as a refrigerant.

Chemistry - Chemical Law

The laws of nature related to chemistry is known as chemical laws.

Chemical reactions, normally, are administrated by certain laws, which are observed and formulated in words become fundamental concepts in chemistry.

Following are the significant chemical laws −

Laws Explanation

Avogadro's Law “Equal volumes of all gases, at the same temperature and pressure, have the same number of molecules”

Beer–Lambert law, (or simply Beer's law or Lambert–Beer law) “Explains the attenuation of light to the properties of the material through which it (light) passes”

Boyle's Law “The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system”

Charles' Law (also known as Law of Volume) “When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be directly related”

Fick's Laws of Diffusion Describes “diffusion” (of flux)

Gay-Lussac's Law "All gases have the same mean thermal expansivity at constant pressure over the same range of temperature"

Le Chatelier's Principle ("The Equilibrium Law") “When any system at equilibrium is subjected to change in concentration, temperature, volume, or pressure, then the system readjusts itself to counteract (partially) the effect of the applied change and a new equilibrium is established”

Henry's Law “The law calculates the concentration of gas in the solution under pressure”

Hess's Law “The change of enthalpy in a chemical reaction (it means, the heat of reaction at constant pressure) is independent of the pathway between the initial and final states”

Law of conservation of energy “Energy can neither be created nor be destroyed”

Raoult's Law “The partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture”

Faraday's Law Electrolysis “The amount of substance produced at an electrode is directly proportional to the quantity of electricity passed”

Atomic Theory “Matter is composed of distinct units known as atoms”

Köhler Theory “Explains the process in which water vapor condenses and forms the liquid cloud drops”

Van 't Hoff Equation “Describes change in the equilibrium constant of a chemical reaction”

Transition State Theory “The reaction rates of elementary chemical reactions”

Grotthuss–Draper Law “It describes that the light which is absorbed by a system/surface can bring a photochemical change”

Kinetic Theory of Gases “Describes the behavior of a hypothetical ideal gas”

Aufbau Principle “Explains that the electrons orbiting the atoms first fill the lowest energy levels and then second higher levels and so on and so forth”

Hund's Rule “ Explains that every orbital in a sublevel is singly occupied before any orbital is doubly occupied”

Collision Theory “Based on the kinetic theory of gases, collision theory describes that the gas-phase chemical reactions occur when molecules collide with sufficient kinetic energy”

Chemistry - Discovery of Elements

Introduction

Most likely copper was the first element, which was mined and used by humans.

The evidence of earliest use of copper was found in Anatolia, which belongs to 6,000 BCE.

The lead was most likely the second element that humans start using.

The oldest known artifact of lead is statuette, which was found in a temple of Osiris, Abydos, Egypt.

The statuette of Osiris temple belongs to (about) 3,800 BCE.

The oldest known gold treasure was discovered in Varna, Necropolis (Bulgaria).

This gold treasure belongs to (about) 4,400 BCE.

Discovery of silver is almost same as of gold; its evidence was found in Asia Minor.

Some evidence say that the iron was known from (about) 5,000 BCE.

The oldest known iron objects, which was used by the humans, were found in Egypt (belongs to 4000 BCE).

The following table illustrates the significant elements with their discovery date and discovers −

Element Discoverer Discovery Date

Copper Middle East (Place) About 9,000 BCE

Lead Egypt (Place) About 7,000 BCE

Gold Bulgaria (Place) About 6,000 BCE

Silver Asia Minor (Place) About 5,000 BCE

Iron Egypt (Place) About 5,000 BCE

Tin

About 3,500 BCE

Sulfur Chinese/India About 2,000 BCE

Mercury Egypt 2,000 BCE

Phosphorus H. Brand 1669

Cobalt G. Brandt 1735

Platinum A. de Ulloa 1748

Nickel F. Cronstedt 1751

Bismuth C.F. Geoffroy 1753

Magnesium J. Black 1755

Hydrogen H. Cavendish 1766

Oxygen W. Scheele 1771

Nitrogen D. Rutherford 1772

Barium W. Scheele 1772

Chlorine W. Scheele 1774

Manganese W. Scheele 1774

Molybdenum W. Scheele 1781

Tungsten W. Scheele 1781

Zirconium H. Klaproth 1789

Uranium H. Klaproth 1789

Titanium W. Gregor 1791

Chromium N. Vauquelin 1797

Beryllium N. Vauquelin 1798

Vanadium M. del Río 1801

Potassium H. Davy 1807

Sodium H. Davy 1807

Calcium H. Davy 1808

Boron L. Gay-Lussac and L.J. Thénard 1808

Fluorine A. M. Ampère 1810

Iodine B. Courtois 1811

Lithium A. Arfwedson 1817

Cadmium S. L Hermann, F. Stromeyer, and J.C.H. Roloff 1817

Selenium J. Berzelius and G. Gahn 1817

Silicon J. Berzelius 1823

Aluminium H.C.Ørsted 1825

Bromine J. Balard and C. Löwig 1825

Thorium J. Berzelius 1829

Lanthanum G. Mosander 1838

Rubidium R. Bunsen and G. R. Kirchhoff 1861

Thallium W. Crookes 1861

Indium F. Reich and T. Richter 1863

Helium P. Janssen and N. Lockyer 1868

Neon W. Ramsay and W. Travers 1898

Xenon W. Ramsay and W. Travers 1898

Fermium A. Ghiorso et al 1952

Nobelium E. D. Donets, V. A. Shchegolev and V. A. Ermakov 1966

Dubnium A. Ghiorso, M. Nurmia, K. Eskola, J. Harris and P. Eskola 1970

Tennessine Y. Oganessian et al 2010

Chemistry - Elements With Their Valence

The following table illustrates significant elements and their valence −

Element Valence Symbol Atomic No.

Hydrogen -1, +1 H 1

Helium 0 He 2

Lithium 1 Li 3

Beryllium 2 Be 4

Boron 3, 2, 1 B 5

Carbon -1, -2, -4, 4, 3, 2, 1, C 6

Nitrogen 0, -1, -2, -3,0, 5, 4, 3, 2, 1, N 7

Oxygen -1, -2, 0, 2, 1, O 8

Fluorine -1, 0 F 9

Neon 0 Ne 10

Sodium -1, 1 Na 11

Magnesium 2 Mg 12

Aluminum 3, 1 Al 13

Silicon -1, -2, -4, 4, 3, 2, 1 Si 14

Phosphorus -1, -2, -3, 0, 5, 4, 3, 2, 1 P 15

Sulfur -1, -2, 0, 6, 5, 4, 3, 2, 1 S 16

Chlorine -1, -2, 0, 6, 5, 4, 3, 2, 1 Cl 17

Argon 0 Ar 18

Potassium -1, 1 K 19

Calcium 2 Ca 20

Scandium 3, 2, 1 Sc 21

Titanium -1, -2, 0, 4, 3, 2, Ti 22

Vanadium -1, -2, 0, 5, 4, 3, 2, 1 V 23

Chromium -1, -2, -3, -4, 0, 6, 5, 4, 3, 2, 1 Cr 24

Manganese -1, -2, -3, 0, 7, 6, 5, 4, 3, 2, 1 Mn 25

Iron -1, -2, 0, 6, 5, 4, 3, 2, 1 Fe 26

Cobalt -1, 0, 5, 4, 3, 2, 1 Co 27

Nickel -1, 0, 6, 4, 3, 2, 1 Ni 28

Copper 4, 3, 2, 1, 0 Cu 29

Zinc 2, 1, 0 Zn 30

Gallium 3, 2, 1 Ga 31

Germanium 4, 3, 2, 1 Ge 32

Arsenic -3, 5, 3, 2, As 33

Selenium -2, 6, 4, 2, 1 Se 34

Bromine -1, 0, 7, 5, 4, 3, 1 Br 35

Krypton 2, 0 Kr 36

Rubidium -1, 1 Rb 37

Strontium 2 Sr 38

Yttrium 3, 2 Y 39

Zirconium 0, -2, 4, 3, 2, 1 Zr 40

Niobium -1, -3, 0, 5, 4, 3, 2, 1 Nb 41

Molybdenum -1, -2, 0, 6, 5, 4, 3, 2, 1 Mo 42

Technetium -1, -3, 0, 7, 6, 5, 4, 3, 2, 1 Tc 43

Ruthenium -2, 0, 8, 7, 6, 5, 4, 3, 2, 1 Ru 44

Rhodium -1, 0, 6, 5, 4, 3, 2, 1 Rh 45

Palladium 4, 2, 0 Pd 46

Silver 3, 2, 1, 0 Ag 47

Cadmium 2, 1 Cd 48

Indium 3, 2, 1 In 49

Tin -4, 4, 2 Sn 50

Antimony -3, 5, 3 Sb 51

Tellurium -2, 6, 5, 4, 2, 1 Te 52

Iodine -1, 0, 7, 5, 3, 1 I 53

Xenon 8, 6, 4, 3, 2, 0 Xe 54

Cesium -1, 1 Cs 55

Barium 2 Ba 56

Lanthanum 3, 2 La 57

Cerium 4, 3, 2 Ce 58

Praseodymium 4, 3, 2 Pr 59

Neodymium 4, 3, 2 Nd 60

Promethium 3 Pm 61

Samarium 3, 2 Sm 62

Europium 3, 2 Eu 63

Gadolinium 3, 2, 1 Gd 64

Terbium 4, 3, 1 Tb 65

Dysprosium 4, 3, 2 Dy 66

Holmium 3, 2 Ho 67

Erbium 3 Er 68

Thulium 3, 2 Tm 69

Ytterbium 3, 2 Yb 70

Lutetium 3 Lu 71

Hafnium 4, 3, 2, 1 Hf 72

Tantalum -1, -3, 5, 4, 3, 2, 1 Ta 73

Tungsten -1, -2, -4, 0, 6, 5, 4, 3, 2, 1 W 74

Rhenium -1, -3, 0, 7, 6, 5, 4, 3, 2, 1 Re 75

Osmium -2, 0, 8, 7, 6, 5, 4, 3, 2, 1 Os 76

Iridium -1, 0, 6, 5, 4, 3, 2, 1 Ir 77

Platinum 6, 5, 4, 2, 0 Pt 78

Gold -1, 0, 7, 5, 3, 2, 1 Au 79

Mercury 2, 1 Hg 80

Thallium 3, 1 Tl 81

Lead 4, 2 Pb 82

Bismuth -3, 5, 3, 1 Bi 83

Polonium -2, 6, 4, 2 Po 84

Astatine -1, 7, 5, 3, 1 At 85

Radon 2, 0 Rn 86

Francium 1 Fr 87

Radium 2 Ra 88

Actinium 3 Ac 89

Thorium 4, 3, 2 Th 90

Protactinium 5, 4, 3 Pa 91

Uranium 6, 5, 4, 3, 2 U 92

Neptunium 7, 6, 5, 4, 3, 2 Np 93

Plutonium 7, 6, 5, 4, 3, 2 Pu 94

Americium 7, 6, 5, 4, 3, 2 Am 95

Elements With Their Atomic Number

Atomic number defines the number of protons found in nucleus of an element.

The total number of protons and neutrons (found in nucleus) is calculated as the atomic mass number.

The following table illustrates the some of the significant elements with their atomic number, atomic mass, and symbols −

Element Atomic Number Atomic Mass (g mol-1) Symbol

Hydrogen 1 1.0079 H

Helium 2 4.00 He

Lithium 3 6.94 Li

Beryllium 4 9.01 Be

Boron 5 10.81 B

Carbon 6 12.01 C

Nitrogen 7 14.0067 N

Oxygen 8 16.00 O

Fluorine 9 19.00 F

Neon 10 20.1797 Ne

Sodium 11 22.989768 Na

Magnesium 12 24.3050 Mg

Aluminum 13 26.981539 Al

Silicon 14 28.0855 Si

Phosphorus 15 30.973762 P

Sulfur 16 32.066 S

Chlorine 17 35.4527 Cl

Argon 18 39.948 Ar

Potassium 19 39.0983 K

Calcium 20 40.078 Ca

Scandlum 21 44.955910 Sc

Titanium 22 47.867 Ti

Vanadium 23 50.9415 V

Chromium 24 51.9961 Cr

Manganese 25 54.93805 Mn

Iron 26 55.845 Fe

Cobalt 27 58.93320 Co

Nickel 28 58.6934 Ni

Copper 29 63.546 Cu

Zinc 30 65.39 Zn

Gallium 31 69.723 Ga

Germanium 32 72.61 Ge

Arsenic 33 74.92159 As

Selenium 34 78.96 Se

Bromine 35 79.904 Br

Krypton 36 83.80 Kr

Rubidium 37 85.4678 Rb

Strontium 38 87.62 Sr

Yttrium 39 88.90585 Y

Zirconium 40 91.224 Zr

Niobium 41 92.90638 Nb

Molybdenum 42 95.94 Mo

Technetium 43 97.9072 Te

Ruthenium 44 101.07 Ru

Rhodium 45 102.90550 Rh

Palladium 46 106.42 Pd

Silver 47 107.8682 Ag

Cadmium 48 112.411 Cd

Indium 49 114.818 In

Tin 50 118.710 Sn

Antimony 51 121.760 Sb

Tellurium 52 127.60 Te

Iodine 53 126.90447 I

Xenon 54 131.29 Xe

Cesium 55 132.90543 Cs

Barium 56 137.327 Ba

Lanthanum 57 138.9055 La

Cerium 58 140.115 Ce

Praseodymium 59 140.90765 Pr

Neodymium 60 144.24 Nd

Promethium 61 144.9127 Pm

Samarium 62 150.36 Sm

Europium 63 151.965 Eu

Gadolinium 64 157.25 Gd

Terbium 65 158.92534 Tb

Dysprosium 66 162.50 Dy

Holmium 67 164.93032 Ho

Erbium 68 167.26 Er

Thulium 69 168.93421 Tm

Ytterbium 70 173.04 Yb

Lutetium 71 174.967 Lu

Hafnium 72 178.49 Hf

Tantalum 73 180.9479 Ta

Tungsten 74 183.84 W

Rhenium 75 186.207 Re

Osmium 76 190.23 Os

Iridium 77 192.217 Ir

Platinum 78 195.08 Pt

Gold 79 196.96654 Au

Mercury 80 200.59 Hg

Thallium 81 204.3833 Tl

Lead 82 207.2 Pb

Bismuth 83 208.98037 Bi

Polonium 84 208.9824 Po

Astatine 85 209.9871 At

Radon 86 222.0176 Rn

Francium 87 223.0197 Fr

Radium 88 226.0254 Ra

Actinium 89 227.0278 Ac

Thorium 90 232.0381 Th

Protactinium 91 231.0388 Pa

Uranium 92 238.0289 U

Neptunium 93 237.0482 Np

Plutonium 94 244.0642 Pu

Americium 95 243.0614 Am

Curium 96 247.0703 Cm

Berkelium 97 247.0703 Bk

Californium 98 251.0796 Cf

Einsteinium 99 252.083 Es

Fermium 100 257.0951 Fm

Mendelevium 101 258.10 Md

Nobelium 102 259.1009 No

Lawrencium 103 262.11 Lr

Unnilquadium 104 261.11 Unq

Unnilpentium 105 262.114 Unp

Unnilhexium 106 263.118* Unh

Unnilseptium 107 262.machines

Chemistry - Nobel Prize

Jacobus Henricus van 't Hoff (a scientist of the Netherlands) was the first person who received the Nobel Prize in Chemistry in 1901.

Jacobus Henricus received the Nobel award for his work namely ‘the laws of chemical dynamics and osmotic pressure in solutions.’

Starting from the 1901 to 2016, total 174 scientists (of chemistry) have been received the Nobel Prize.

By the time, four women have been received the Nobel Prize in chemistry.

Marie Curie was the first lady who received the Nobel Prize in chemistry.

The following table illustrates the name of individuals who received Nobel Prize in chemistry along with their work (for which they received the Prize) −

Name Country (year) Work/Area

Svante August Arrhenius Sweden (1903) Electrolytic theory of dissociation

Sir William Ramsay UK (1904) Discovery of the inert gaseous elements in air

Ernest Rutherford UK/New Zealand (1908) Chemistry of radioactive substances

Maria Skłodowska-Curie Poland/France (1911) Discovery of the elements radium and polonium

Alfred Werner Switzerland (1913) Linkage of atoms in molecules

Theodore William Richards US (1914) Determinations of the atomic weight

Walter Norman Haworth UK (1937) Investigations on carbohydrates and vitamin C

Paul Karrer Switzerland (1937) investigations on carotenoids, flavins and vitamins A and B2

Adolf Friedrich Johann Butenandt Germany (1939) Work on s*x hormones

Otto Hahn Germany (1944) Discovery of the fission of heavy nuclei

John Howard Northrop & Wendell Meredith Stanley US (1946) Preparation of enzymes and virus proteins in a pure form

Vincent du Vigneaud US (1955) First synthesis of a polypeptide hormone

Sir Cyril Norman Hinshelwood & Nikolay Nikolaevich Semenov UK & Soviet Union (1956) Mechanism of chemical reactions

Frederick Sanger UK (1958) The structure of proteins (especially insulin)

Willard Frank Libby US (1960) Method to use carbon-14 for age determination

Melvin Calvin US (1961) Carbon dioxide assimilation in plants

Karl Ziegler & Giulio Natta Germany & Italy (1963) Chemistry and technology of high polymers

Dorothy Crowfoot Hodgkin UK (1964) Determinations by X-ray techniques

Paul J. Flory US (1974) Physical chemistry of macromolecules

Paul Berg US (1980) recombinant-DNA

Aaron Klug UK (1982) Development of crystallographic electron microscopy

Henry Taube US (1983) Mechanisms of electron transfer reactions

Robert Bruce Merrifield US (1984) Methodology for chemical synthesis on a solid matrix

Elias James Corey US (1990) Methodology of organic synthesis

Richard R. Ernst Switzerland (1991) Methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy

Kary B. Mullis US (1993) Polymerase chain reaction (PCR) method

George A. Olah US & Hungary (1994) Carbocation chemistry

Peter Agre US (2003) Discovery of water channels (cell membranes)

Roger D. Kornberg US (2006) Molecular basis of eukaryotic transcription

Gerhard Ertl Germany (2007) Chemical processes on solid surfaces

Venkatraman Ramakrishnan, Thomas A. Steitz, & Ada E. Yonath 2009 Structure and function of the ribosome

Tomas Lindahl, Paul L. Modrich, & Aziz Sancar 2015 DNA repair

Jean-Pierre Sauvage, Fraser Stoddart, & Ben Feringa 2016 Design and synthesis of molecular machines.

Chemistry - Atoms & Molecules

Introduction

Around 500 BC, an Indian Philosopher Maharishi Kanad, first time postulated the concept of indivisible part of matter and named it ‘pramanu.’

In 1808, John Dalton used the term ‘atom’ and postulated the atomic theory to the study of matter.

John Dalton

Dalton’s Atomic Theory

According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms.

According to Dalton’s atomic theory, all matters, whether they are elements, compounds, or mixtures, are composed of small particles known as atoms.

Salient features of Dalton’s Atomic Theory

All matter is made of very miniscule particles known as atoms.

Atom is an indivisible particle, which cannot be created or destroyed through chemical reaction.

All atoms of an element are identical in mass and chemical properties whereas, atoms of different elements have different masses and chemical properties.

To form a compound, atoms are combined in the ratio of small whole numbers.

In a given compound, the relative number and kinds of atoms are constant.

Atomic Mass

The mass of an atom of a chemical element; it is expressed in atomic mass units (symbol is u).

The atomic mass is roughly equivalent to the number of protons and neutrons present in the atom.

One atomic mass unit is a mass unit equal to the exactly one-twelfth (1/12th) the mass of one atom of carbon-12 and the relative atomic masses of all elements have been calculated with respect to an atom of carbon-12.

Molecule

The smallest particle of an element or a compound, which is capable to exist independently and shows all the properties of the respective substance.

Molecule

A molecule, normally, is a group of two or more atoms which are chemically bonded together.

Atoms of the same element or of different elements can join (with chemical bond) together to form molecules.

The number of atoms that constitute a molecule is known as its atomicity.

Ion

A charged particle is known as ion; it could be either negative charge or positive charge.

The positively charged ion is known as a ‘cation’.

The negatively charged ion is known as an ‘anion.’

Chemical Formulae

A chemical formula of a compound demonstrations its constituent elements and the number of atoms of each combining element.

Chemical Formulae

The chemical formula of a compound is the symbolic representation of its Composition.

The combining capacity of an element is known as its ‘valency.’

Molecular Mass

The molecular mass of a substance is calculated by taking the sum of the atomic masses of all the atoms in a molecule of respective substance. For example, the molecular mass of water is calculated as −

Atomic mass of hydrogen = 1u

Atomic mass of oxygen = 16 u

The water contains two atoms of hydrogen and one atom of oxygen.

Molecular Mass of Water is = 2 × 1+ 1×16 = 18 u (u is the symbol of molecular mass).

Formula Unit Mass

The formula unit mass of a substance is calculated by taking the sum of the atomic masses of all atoms in a formula unit of a compound.

Avogadro Constant or Avogadro Number

Avogadro was an Italian scientist who had given the concept of Avogadro Number (also known as Avogadro Constant).

The number of particles (atoms, molecules, or ions) present in 1 mole of any substance is fixed, and its value always calculated as 6.022 × 1023.

In 1896, Wilhelm Ostwald had introduced the concept of ‘mole;’ however, mole unit was accepted to provide a simple way of reporting a large number in 1967.

Law of Conservation of Mass

During a chemical reaction, sum of the masses of the reactants and products remains unchanged, which is known as the ‘Law of Conservation of Mass.’

Law of Definite Proportions

In a pure chemical compound, its elements are always present in a definite proportion by mass, which is known as the ‘Law of Definite Proportions.’

Energy Levels

Bohr represented these orbits or shells are by the letters K, L, M, N,… or the numbers, n = 1,2,3,4,….

Neutron

In 1932, J. Chadwick discovered a new sub-atomic particle i.e. neutron.

Neutron has no charge and a mass nearly equal to that of a proton.

Neutrons are present in the nucleus of all atoms, except hydrogen.

Electrons Distributed in Different Orbits (Shells)

The maximum number of electrons that can be present in a shell is given by the formula 2n2.

‘n’ is the orbit number or energy level index, i.e. 1, 2, 3,….

According to the given formula −

First orbit i.e. K-shell will be = 2 × 12 = 2

Second orbit i.e. L-shell will be = 2 × 22 = 8

Third orbit i.e. M-shell will be = 2 × 32 = 18

Fourth orbit i.e. N-shell will be = 2 × 42 = 32

Likewise, the maximum number of electrons that can be accommodated in the outermost orbit is 8.

Electrons are not filled in a given shell, unless the inner shells are filled. It means, the shells are filled in a step-wise manner; starting from inner shell to outer shell.

Valence

The electrons, those are present in the outermost shell of an atom, are known as the valence electrons.

According to Bohr-Bury model, the outermost shell of an atom can have a maximum of 8 electrons.

Atomic Number

The total number of protons, present in the nucleus of an atom, is known as atomic number.

The number of protons of an atom determines the atomic number.

Atomic number is denoted by ‘Z’.

Protons and neutrons collectively are known as nucleons.

Mass Number

The sum of the total number of protons and neutrons, present in the nucleus of an atom, is known as mass number.

Isotopes

The atoms of the same element, having the same atomic number but different mass numbers, is known as isotopes. E.g. Hydrogen atom has three isotopes namely protium, deuterium, and tritium.

The chemical properties of isotopes of an atom are similar but their physical properties are different.

Isobars

Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars. E.g. calcium’s atomic number is 20and argon’s atomic number is 18;

Chemistry - Carbon and its Compounds

Introduction

Carbon plays very important roles for all living beings.

The amount of carbon in the earth’s crust is merely 0.02%, which is available in the form of minerals such as carbonates, hydrogen-carbonates, coal, and petroleum.

The presence of carbon in the atmosphere of the earth is 0.03%, in the form of carbon dioxide.

Compounds of Carbon

Almost all carbon compounds (except a few) are poor conductors of the electricity.

The diamond and graphite both are formed by carbon atoms; however, the difference lies between them in the manner in which the carbon atoms are bonded to one another.

In diamond, each atom of the carbon, is bonded to four other carbon atoms and form a rigid three-dimensional structure (see the image given below).

Diamond Structure

In graphite, each atom of the carbon, is bonded to three other carbon atoms in the same plane, which gives a hexagonal array (see the image given below) −

graphic Structure

There is also difference in some physical structure of diamond and graphite.

Diamond is the hardest substance known whereas graphite is smooth and slippery substance.

Graphite is good conductor of electricity.

Following table illustrates the structures of compounds of carbon and hydrogen −

Name Formula Structure

Methane CH4 Methane Structure

Ethane C2H6 Ethane Structure

Propane C3H8 Propane Structure

Butane C4H10 Butane Structure

Pentane C5H12 Pentane Structure

Hexane C6H14 Hexane Structure

The compounds, which has identical molecular formula, but different structures, are known as structural isomers (see the structure Butane given below).

Structure Butane

The saturated hydrocarbons are known as alkanes.

The unsaturated hydrocarbons, which comprise of one or more double bonds, are known as alkenes.

The unsaturated hydrocarbons, which comprise of one or more triple bonds, are known as alkynes.

Use of Alcohol as Fuel

Sugarcane plants very efficient convert sunlight into chemical energy and its juice can be used to prepare molasses.

When molasses is fermented, it produces alcohol (ethanol).

Some of the countries now using alcohol as an additive in petrol, as it is a cleaner fuel.

These alcohol, on burning in sufficient air (oxygen), gives rise to only carbon dioxide and water.

Esters

Esters are sweet-smelling substances, which are most commonly formed by reaction of an acid and an alcohol (see the image below – illustrating the formation of esters).

Formation of Esters

When esters react in the presence of an acid or a base, it gives back the alcohol and carboxylic acid.

The reaction of esters with an acid or a base, is known as saponification because it is used in the preparation of soap.

The molecules of soap normally are sodium or potassium salts of long-chain carboxylic acids.

Interestingly, the ionic-end of soap dissolves in water whereas the carbon chain dissolves in oil. This typical features of the soap molecules forms structures known as micelles (see the image given below)

Micelles

In micelles, one end of the molecules is towards the oil droplet whereas the ionic-end remains outside.

The soap micelle helps in dissolving the dirt in water; likewise, the clothes get cleaned.

On the other hand, detergents are usually ammonium or sulphonate salts of long chain carboxylic acids, which remain effective even in hard water.

Detergents are customarily used to make shampoos.

Hacker Jan.