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Saturday, 26 September 2015

FSc Notes Chemistry Part 1 Chapter 1 Basic Concepts Lecture 1

FSc Notes Chemistry Part 1 Chapter 1 Basic Concepts

Science

The study of all the things of universe is called science.
Or
The knowledge based on observations experiments and results is called science.

At the beginning, science was named as Natural Philosophy and it had two branches.
  1. Biological Science
  2. Physical Science
Biological Science
As there are only two types of living things from the beginning ie Animals and plants, so Biological science got two main farther subjects ie Botany ( from Greek word Botany -----Herbs study plants ). Zoology ( from Greek word Zoo --- Animal ).
Physical Science
On the other hand with the passage of time more and more development took place, in physical science, therefore it is divided into the following main branches . Physics ,Chemistry, Math, Computer Astronomy etc.

Matter:

Anything which has mass and volume is called matter
Or
Anything having mass and volume is called matter e.g Pen, Air, Water, etc

States of matter.

  1. Solid state
  2. Liquid state
  3. Gaseous state
  4. Plasma state

Chemistry:

Is that branch of science which deals with the properties, compositions and structure of matter, changes occurring in matter and the laws under which these changes occur.

Branches of Chemistry:

With the passage of time, more and more development took place in chemistry, therefore it was felt necessary to divide chemistry into various branches to make its study more convenient and systematic, chemistry has been divided into the following important branches.

Organic Chemistry:
The carbon containing compounds ( except CO2, CO, CO3 -2, HCO3- 1 & CN ) are called organic compounds and their study is called organic chemistry.
Inorganic Chemistry:
The study of all the elements and compounds of the elements other than carbon is called inorganic chemistry .
Physical Chemistry:
The branches of chemistry dealing with the study of laws and principles which are responsible for the separation and combination of atoms during chemical reaction called physical chemistry.
Analytical Chemistry:
The study of qualitative and quantitative analysis of a substance is called analytical chemistry.
Biochemistry:
The study of chemical reactions place inside the body of living things is called biochemistry.
Industrial Chemistry:
The study of chemical reactions occurring during the formation of various synthetic products like content, glass, plastic etc in industries is called industrial chemistry.
Nuclear Chemistry:
The study of changes occurring in the nuclei of radio active elements as a result of spontaneous emission of radiations & their effects is called nuclear chemistry.
Environmental Chemistry:
The study of chemical reactions taking place in the environment and their effects upon us is called environmental chemistry.

Atom:

The smallest particle of matter which may or may not have free existence is called atom, For example hydrogen element is composed of H atoms which don’t have free existence. Similarly Helium element is composed of He atoms which have free existence.
The word Atom is derived from a Greek word, Atoms which means indivisible. This name was given by Democritus / 460-370 B.C. Actually the Greek, philosophers thought that matter could be divided into smaller and smaller particles to into smaller and smaller particles to reach a basic unit, that can not be further sub-divided. According to the modern concepts, atom is further composed of sub-atomic particles which are more than 100. however there are the fundamental ones they are:
  1. Proton
  2. Electron
  3. Neutron
All the particles of an atom are inside the nucleus of it. Only electrons are present outside, the nucleus, revolving around it. A Swedish chemist. Named as J. Berzelius ( 1779-1848) determined the atomic masses of elements. He also provided the system of giving symbols to elements.

Elements:

Element is a pure substance, which is composed of chemically identical atoms. e.g.; hydrogen is an element which consists of it atoms which are all chemically identical y the term chemically.

Substance:

Any pure matter which a uniform composition is known as substance. e.g.; elements, compound, molecule etc.
Identical means that all atoms of an element will have same number of protons and same no. of electrons. However their number of neutrons mean be different.
H --> element H,H,H,H,H,H ---> Atoms
So far more than 110 elements are known. Most of them are natural while some are synthetic,
Types:- Elements are of the following three types.
  1. Metals
  2. Non-metals
  3. Metalloids

Metals
  • They are hard solids excepts Hg which is liquid
  • There have shine
  • They are good conductors of heart & electricity
  • Some metals are ductile i.e.; their wires can be format
  • They have light melting point & boiling point.
  • Examples Na, K, Mg, Cu, Ag, Au, Me etc.

Non-Metals:
  • They may be solid, liquid or gases
  • They have no shine
  • They are bad conductors except graphite
  • Non-metals are brittle, i.e.; their & some are malleable i.e.; their sheets can be formed wires & sheets cannot be formed.
  • They have low melting point & boiling point.
  • Examples i. Sold:- C, S, P etc ii. Liquid:- Br. iii. Gas:- H2, U2, O2 etc.

Metalloids:
  • The elements which have properties in between metals and non-metals. e.g.; Ga, Ge. Etc.

Compound:

When atoms of two or more elements chemically combine in a fixed ratio, a new substance is formed. Which is known as compound.
For example when two atoms of hydrogen element chemically combine with one atom of oxygen element, a compound, water (H2O) is formed in which the atoms are combined in 2:1

Molecule:

The smallest particle of a substance which is capable of free existence is known as molecule. e.g.; H2O, H2, O2 etc.

Classification of Molecules:

Molecules can be classified in two ways as:
 

On the basis of nature of elements:

On the basis of nature of elements, there are two types of molecule
  1. Molecule of Elements: The molecules which are made of atoms of same elements. e.g.: H2, O2, O3, S8, P4, N2, U2 etc.
  2. Molecule of Compound: The molecules which are made of atoms of different elements. e.g.: H2O,  H2, SO4, C6H12 06 etc.

On the basis of number of atoms.

On the basis of no. of atoms there are three types of molecules, which are described as follow.
  1. Mono-atomic molecules: The molecules which are made of only one atom are called mono-atomic molecules. e.g.; He, Ne, Xe etc.
  2. Diatomic molecules: The molecules which are made of only two atoms (same or different). e.g.; H2, N2, CO,  U2 etc.
  3. Poly atomic molecules: The molecules which are made of more than two atoms are called ply atomic atoms are called poly atomic molecules. e.g.; H2O, H2 SO4, C6 H12O6, CH4, NH3 etc.

Formula Unit:

The simplest combination of atoms of a compound which possesses all the called formula unit. For example NaU is a formula unit. Sodium chloride is a cluster of NaT & U Ions and each U ion is surrounded by 6 NaT & U ions of sodium chloride there is no independent NAu Unit. Therefore, NaU is termed as formula unit rather than molecule. All ionic compounds are represented by formula units.

Isotopes:

Isotopes of an element may be defined as:
"The atoms of an element having same atomic number but different atomic masses, are called isotopes of that elements."
OR "Atoms of an element having same no. of protons and same no. of electrons but different no. of neutrons are called isotopes of that elements.
OR " Atoms of an element having same chemical properties but different physical properties are called isotopes of that element.

For example carbon element has three isotopes. Which are known as C-12, C-13, & C-14. All these isotopes of carbon have same no. of protons (e.g.; b) & same no. of electron (i.e.;6) but different no. of neutrons i.e.; 6,7 and 8 respectively in C-12, C-13, & C-14. Other examples are, Hydrogen has 3 isotopes, oxygen has three, Nickle ( Ni ) has five, calcium has six, palladium has six, cadmium has nine and tin has 2 isotopes.

Round about 280 natural isotopes are known 40 of them are radio active isotopes. Beside these 280, about 300 unstable radio active artificial disintegration. Elements like Arsenic (As), fluorine (F), iodine ( I ) and gold ( Au ) etc, have only a single isotope. It important to note that elements of odd atomic number almost never possess more that two stable isotopes. On the other hand elements of even atomic number usually have larger number of isotopes. The isotopes whose mass number are multiple of 4, are particularly abundant out of 280 isotopes that occur in nature, 154 have even mass number, and even atomic number.

Ion:

When an atom loses or gains one or more electrons have 8 electrons in their outermost (valence ) shell, they get a tire of –ve sign. This positively or negatively changed species is known as ion.
e.g.
Electron configuration of
Na is K=2 , l=8, M=1
So sodium loses its single valence electron & thus forms sodium ion ( Na+ ). Such an ion having + ve charge is called cation
Na ----------------------- Na+ + Ie-
2, 8
Similarly the electronic configuration on of 17CL is k=2, L=8, M=7 so it gains an electron to
form chloride ion ( Cl -1 )
i. e Cl + Ie- ---------------------------- Cl-1
2, 8, 12
The ion having negative change is called “Anion ". It is important to note that properties of ions are totally different from their corresponding neutral atoms. The ions may be a group of atoms like
-2 , Co3
-2, Hco3
-1 , no4
-1 , Cr2O7
-2, PO4

The + ve ion common e.g. NH4 + ion and some carbon cations in organic chemistry.

Ion are always stable inside their solution E.g.: Na+ & CL- ions are always stable inside water.

Molecular Ion:

When a molecule loses or gains electron or electrons which is known as molecular ion. e. g CH4 + , N2 + , CO+ etc. The cationic molecular ions ( +ve ) are more abundant than the anionic ones. Molecular ions are formed by passing high speed electrons or x—particles through a gas.

Radical:

Any negatively or positively charged species or a specie with unpaired electron, which is unable to have free existence is known as radical. e. g H. + CL. ( Neutral radicals with unpaired electron )


Atomic Number:

The no of protons or electrons present in an atom is called atomic number of that element. For example there are 11 protons and 11 electrons in an atom of sodium element, therefore atomic mass of sodium is 11.

Atomic Mass or Mass No:
Sum of the protons and neutrons present in the nucleus of an atom is called the atomic mass of that atom.
e. g There are 11 protons ans 12 neutrons in the nucleus of Na atom, therefore the atomic mass of Na will be: 11 + 12 ======= 23 a. m. u

Relative Atomic Mass:

The mass of one atom of an element compared with the mass of one atom of corbon – 12 is called relative atomic mass of that element. Carbon- 12 ( C-12 ) which is an isotopes of carbon element and it is considered as standard. It mass is considered as exactly 12 a.m. u The masses of all the other elements are compared with the mass of C- 12 which are known as their relative atomic mass.

The unit of atomic mass is a. m. u ie atomic mass unit.

Atomic Mass Unit ( A. M. U )

It may be defined as the 12th part of the mass of an atom of C-12
Or
The mass of an atom of E-12 divided by 12 is known as one a. m. u. Let the mass of an atom of C-12 is Xg, then value of one a.m.u will be:
1 a. m. u = x = 12
E.g. : the mass of an atom of hydrogen id 0.084 times the mass of C-12, so the relative atomic mass of Hydrogen is 0.084* 12===1.008 a. m. u.
We can find the mass of one atom of C-12 as follow. As atomic mass of C-12 = 12g which is equal to one mole of carbon – 12 containing 6.023*1023 C-12 atoms i.e.
12g of C= 6.023 * 1023
1 a.m. u = 1.99*10-23/12
1 a.m. u = 1.66*10-24

Relative Molecular Mass:

Sum of the relative atomic masses of all the elements present in a molecule is called as relative molecular mass of that molecule. For example


Average Atomic Mass:

The average of the atomic masses of all the isotopes of an element with respect t their relative abundance is known as average atomic mass of that element for the determination of the average atomic mass of an element we multiply the masses of all the isotopes with relative abundance and then add then up and finally divide them by 100.


Relative Abundance:

The no of atoms of an isotopes of an element present in 100 atoms of element is known as relative abundance of that isotope.
Eg if we take 100 atoms of Hydrogen element & let the no of protium atoms is 97 that of deuterium atoms is 2 and that of tritium, atoms is 1. Thus we can say that the relative abundance of protium is 97% , Deuterium is 2% and tritium is 1 % .

Written by: Asad Hussain

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