CHEMISTRY

BASICS 

FATHER OF CHEMISTRY: Antoine Lavoisier

ATOM:

An atom is a negligible particle. atom is indivisible.we can't see the atom with the human eye.
an atom consists of 3 elements named as: proton, electron, neutron. Around 450 B.C, the Greek philosopher Democritus introduced the thought of the atom. However, the thought was essentially forgotten quite 2000 years. In 1800, John Dalton scientist re-introduced the atom.

proton: 

proton is an element in the atom. every atom consists of its own molecules. proton is a positively charged particle. proton was covered in the anode rays experiment.proton was discovered by the E.GOLDSTEIN. the mass of the proton is 1.00728 a.m.u. the charge of the proton is +1.

electron:

electron is a negatively charged particle. electron is invented by the JJ THOMSON by the cathode rays experiment. the mass of the electron is 0.005486. the charge of the electron is -1.

neutron:

the neutron is a negatively charged particle. the neutron was invented by the JAMES CHADWICK by the bombardment of Beryllium alpha particles. the mass of the neutron is 1.008665 a.m.u. charge of the neutron is zero.

nucleus:

the nucleus is a central part of an atom. here the electrons, protons are revolved around its orbit.

atomic number:

the atomic number denotes the number of protons present in the nuclei of an atom. it is generally indicated with the letter"Z".

mass number:

the sum of the number of protons and electrons in the nuclei of an atom is called MASS NUMBER.
it is indicated with the letter"A".

Atomic number(Z)=number of protons=number of electrons

Mass number(A)=(Z)+number of neutrons

ex:- hydrogen element=protons(1),electron(1)
number of neutrons=(A)-(Z)
then the neutrons=0


BOHR'S ATOMIC THEORY:

Neil's Bohr proposed the model of an atom based on the atomic spectra of hydrogen.

postulates:

-electrons revolve around the nucleus with high velocity in circular paths called orbits or shells.
-electron in a particular orbit, it's energy is constant.these orbits are called stationary orbits.
-the stationary orbits have the energy levels and they are named as K(1), L(2), M(3), N(4)...etc.,
-when the electrons jump from one energy level to another energy level it causes an energy difference called radiation quanta.

E2-E1=hU

h=planck's constant(6.625*10^-34 J.sec)
U=frequency of radiation

Angular momentum;
m*v*r=n h/2*3.14

m=mass of an electron;
v=velocity of an electron;
r=radius of an orbit;
h=planck's constant;
n=integer(orbit number1,2,3,4...)

MERITS:

-bohr's theory explains the spectral series of hydrogen and lithium like similar ions.

LIMITATIONS:

• could not explain the spectral series of more than an atom.
• bohr's theory could not explain the splitting of an atom by the (Zeeman)magnetic effect and(stark)electric effect.
• and also could account for the formation of chemical bonds.

QUANTUM NUMBERS:

the quantum numbers are used to specify and arrange an electron in a specific order.
quantum numbers are four types:
1-principal quantum number
2-azmithul quantum number
3-magnetic quantum number
4-spin quantum number

PRINCIPAL QUANTUM NUMBER:

-the principal quantum number was proposed by the NEIL'S BOHR.
-the principal quantum number is denoted with the letter"n".
-this explains about size and energy of a stationary orbit.
-the number of orbital in a given shell is "n^2".
-the maximum number of electrons in a principal quantum number is given by "2n^2"

AZIMUTHAL QUANTUM NUMBER:

-the azmithul quantum number was proposed by the SOMMERFELD.
-it is indicated by the letter"l".
-it gives the shape of an orbital.
-the l value starts from 0,1,2,3...
-  0=s
   1=p
   2=d
   3=f
-another name of this quantum number is an angular quantum number.

MAGNETIC QUANTUM NUMBER:

-this is proposed by the LANDE.
-it is indicated with the letter "m".
-the magnetic quantum number gives the orientation of orbitals in a space.
-it represents the number of orbitals present in a given subshell.

SPIN QUANTUM NUMBER:

-this is proposed by the UHLENBECK AND GOUDSMIT.
-it is indicated with the letter"s".
-it gives the spin of an electron about its own axis.
- +1/2 clockwise spin and -1/2 anticlockwise spin.
-each orbital consists of two electrons with opposite spin.

ELECTRONIC CONFIGURATION:

The arrangement of electrons in various orbitals of an atom is called electronic configuration.

the electronic configuration is two types:
1- nl^x method
2- box method

(1) the 'n' 'l' represents the principal and azmithul quantum numbers, the
 power x represents the number of electrons in a subshell.

ex:1 s^2

(2) a subshell is indicated by the square and spin of electrons are indicated by the upward and downward arrows.

there are four principles to describe the arrangement of an electron in an atom:

[1]AUFBAU'S PRINCIPAL

-electrons are added progressively to the various subshells in the order of increasing their energy.

[2]HUND'S RULE

-electrons are started pairing after until each electron filled in a subshell.

[3]PAULI'S EXCLUSION

-No two electrons can have all the four quantum numbers in an atom.

[4]ADDITIONAL STABILITY

-atom gets stable after the electrons completely filled or half-filled in degenerated orbitals.

ORBITAL:

The probability of finding electrons is maximum in a region of space around the nucleus of an atom.

SHAPES OF ORBITAL:

four types are identified and recognized by the shapes and angular momentum of electrons.

S-ORBITAL:

spherical shape

P-ORBITAL:

dumbbell shape

D-ORBITAL:

double dumbbell shape

F-ORBITAL:

it is similar to d orbital but cut in half.


CHEMICAL BONDING:

a strong force of attraction holding the atoms together in a molecule, resulting in the sharing or transferring of electrons.

The electronic theory of valency:

this theory was proposed by the KOSSEL and LEWIS. it explains the chemical bonding in terms of electronic distribution.

valency means the number of electrons present in the outermost orbital of an atom.

the fact attaining 8 electrons configuration in the outermost orbit called OCTET RULE.and those are called stable atoms.


chemical bonds have the following nature:

1-ionic
2-covalent
3-metallic
4-molecular
5-coordinate
6-hydrogen bond

IONIC BOND:

the transfer of electrons from one atom to a different atom is named as IONIC BOND.
and it is also called an electrovalent bond.

COVALENT BOND:

the sharing of electrons from one atom to another atom is called COVALENT BOND.

LEWIS DOT MODEL:

it explains the formation of a covalent bond. the covalent bond is formed by the sharing of electrons in atoms, by the contributing
 one electron to pair in the outermost orbital.

Crystal:

a solid figure which has a definite geometrical shape with sharp edges and flat faces.

Lattice point:

a point at which constituent the particle. these are formed by straight lines.

Unit cell:

the smallest portion of the crystal.

Simple cubic structure:

there are points only at each corner.

Face centered cubic  lattice:

there are points at which each corner and centers of each face in a cube.

Body-centered cubic lattice:

there are points at which all the corners as well as in the body center of the cube.

SOLUTIONS OF CHEMISTRY

The solution is nothing but a homogeneous mixture of substances is called SOLUTION.

the solution consists of two substances one is solute and another one is solvent.

the solute is a substance that has a high concentration and less amount of portion.

the solvent is a substance that has less concentration comparing to solute and a large amount of portion.

solutions are classified into three types:

saturated solutions: the solution in which no more solute can be dissolved in the solvent is called a saturated solution.

unsaturated solution: the solution in which contains less amount of solute compared to the saturation
the solution is called an unsaturated solution.

supersaturated solution: the solution in which contains more than the amount of solute compared to the saturated solution is called a supersaturated solution.

concentration: the amount of solute is dissolved in a definite quantity of solution is called concentration.

MOLE: it is defined as the mass of a substance that contains 6.023*10^23 elementary units.

MOLARITY is defined as the number of moles of the solute present in one liter of solution.

molarity=(W*1000)/(GMW*V)

W stands for a wait of solute.
GMW stands for a gram molecular weight of solute.
V stands for the volume of the solution. (ml)
EWS stands for an equivalent weight of solute.

unit of molarity=(mol.lit^-1)

molarity decreases with the increase in temperature.

NORMALITY is defined, the number of gram equivalents of a solute present in one liter of solution.

normality=(W*1000)/(EMW*V)

i.e for EMW of acid=(GMW / basicity of an acid)
i.e for EMW of base=(GMW / acidity of a base)
i.e for EMW of salts=(GMW / total charge on the cation on anion)

NOTE:

the periodic elements table: