Periodic table
The periodic table is a tabular depiction of the chemical elements and their characteristics. Russian chemist Dmitri Mendeleev is generally credited with the invention of the periodic table. The periodic table lists all the elements, with information about their atomic weights, chemical symbols, and atomic numbers. The vertical columns (groups) of the periodic table are arranged such that all its elements have the same number of valence electrons. A horizontal row in the periodic table, which signifies the total number of electron shells in an element’s atom.
Atom
An atom is made up of three particles, electrons, protons and neutrons. Electrons have a negative charge and protons have a positive charge whereas neutrons have no charge. They are neutral. Due to the presence of equal number of negative electrons and positive protons, the atom as a whole is electrically neutral.

Electrons
and energy levels
The electrons revolve rapidly around the nucleus in fixed circular paths called energy levels, orbits or shells are represented in two ways: either by the numbers 1, 2, 3, 4, 5 and 6 or by letters K, L, M, N, O and P. The energy levels are counted from center outwards. Each energy level is associated with a fixed amount of energy. The shell nearest to the nucleus has minimum energy and the shell farthest from the nucleus has maximum energy.

Shells and subshells
Shells are the circular paths around the nucleus of an atom along which the electrons traverse.Orbitals with the same principal quantum number of n form a shell. Those shells are divided into individual orbitals which are called subshells.Each shell consists of one or more sub-shells. There are four sub-shells - s , p , d ,f .

Bohr’s Atomic Model
Bohr’s Atomic Model  introduced by Danish Physicist Niels Bohr in the year of 1913. According to this model the atom is consists of small nucleus at the center and electrons which rotates in circular orbits surrounding to nucleus - similar to solar system. But here, the force of attraction is provided by electrostatic forces rather than gravitational forces

s-block elements
The elements in which the last electron enters the s-sub- shell of their outermost energy level are called s-block elements.
This block is situated at extreme left of the periodic table. It contains elements of groups 1 and 2. Their general configuration is ns1-2

p-block elements
The elements in which the last electron enters the p-subshell of their outermost energy level are called p-block elements. The ·general configuration of their outermost shell is ns2 np1-4i. The only exception is helium (l s2).
They show variable oxidation states.They form ionic as well as covalent compounds.They have relatively higher values of ionization energy. Most of them are non-metals.

d-Block elements
These elements lie in between s-block and p-block elements. These elements   are called       transition elements as they show transitional properties between s and p-block elements. The general electronic configuration of d-block elements is (n-1)d1-10ns0-2. They are hard, high melting metals. They show variable oxidation states. They form coloured complexes. They form ionic as well as covalent compounds. Most of them possess catalytic properties.

f-block elements
The elements in which the last electron enters the f –sublevel of the anti-penultimate (third to the outermost shell) shell are called f-block elements. Their general configuration is (n – 2)f1-14 (n – 1) d 0-1 , Ns2, where n represents the outermost shell. The elements of first series follow lanthanum (57La) and are called  lanthanoids. The elements of second series follow actinium (89Ac) and are called actinoids .They show variable oxidation states. They have high densities. Most of the elements of actinoid series are radioactive.

Mole and Molar mass
Mole is the amount of substance, which contains as many elementary entities as there are in 12 gram of carbon. Elementary entities may be atoms, molecules, ions, electrons or protons.1mole of a substance always contains the same number of entities irrespective of the identity and kind of the substance.1 mole of Carbon atoms contains 6.022*1023 number of atoms and weighs 12 grams. molar mass defined as mass of 1 mole of substance, expressed in grams. It is numerically equal to atomic mass or molecular mass.Molar mass can be obtained by adding atomic masses of all the atoms present in one molecule of the substance.

Molar volume
The volume occupied by 1 mole of a gas at STP is known as molar volume.
1 mole of CO2 occupies 22.4 liters of volume at STP.

Balanced chemical equation
Every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. Therefore, there must be the same number of atoms of each element on each side of a chemical equation.
Balanced chemical equation for the Combustion of Methane gas in Oxygen.
CH 4 + 2O2 CO2+ 2H2O
Using the mole Concept , 640g   Oxygen   required to react Completely with  160 g CH4 .

Chemical reactions
Chemical reactions take place at different speeds. Some reactions, such as ripening of fruits or rusting of iron, happen over a few weeks and hence are called slow reactions. Reactions which takes longer time for the completion of the reactions are called slow reactions.
Reactions which takes very lesser time for the completion are called fast reactions   An explosion that blasts a rock is an Example of fast reactions. Reactions which takes moderate time for the completion are called moderate reactions .The formation of ammonia and hydrolysis of sugar occur at moderate or medium speeds is an Example of moderate reactions.

catalyst
A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction; hence a catalyst can be recovered chemically unchanged at the end of the reaction it has been used to speed up, or catalyze.

Concentration and
chemical reactions
If the amount of solute In unit volume of the solution is high it’s called Concentrated Solution and solute is low called dilute Solution. For many reactions involving liquids or gases, increasing the concentration of the reactants increases the rate of reaction. The collision theory says that as more collisions in a system occur, there will be more combinations of molecules bouncing into each other. If you have more possible combinations there is a higher chance that the molecules will complete the reaction. The reaction will happen faster which means the rate of that reaction will increase. All Collisions  between reactant molecules need not lead to a chemical reaction. Only the molecules having energy greater than a certain threshold value can undergo effective Collisions leading to the success.

chemical equilibrium
Many chemical reactions are reversible, and the forward and backward reactions can occur at the same time. When the rate of the forward reaction is equal to the rate of the backward reaction, we call that a dynamic equilibrium. We will learn how equilibrium can be described by the equilibrium constant K, and how different factors than can affect the chemical equilibrium.

Reactivity series of metals
Some metals are chemically very reactive but some are less reactive. metals which lose the electrons readily, forming positive ions are more reactive than other metals which do not lose electrons readily. Some metals like alkali & alkaline earth metals are very reactive and  react vigorously with a reactant. But some metals like gold and  platinum are least reactive and passive for almost all reactants. Some metals like copper release hydrogen gas with dilute acid. Hence, there must be some criteria for understanding the reactivity of different metals and predicting the products of different reactions. For example, Zn in metal displaces copper from copper sulphate  solution when zinc  rod is immersed in CuSO4 solution. But copper cannot displace zinc from ZnSO4 solution. Therefore zinc is more reactive than copper. We can arrange the metals in the order of decreasing reactivity for comparison of relative reactivity. The arrangement of metals in the order of decreasing reactivity on the basis of chemical reaction is called reactivity series of metals.

Galvanic cell
A galvanic cell is an electrochemical cell that uses the transfer of electrons in redox reactions to supply an electric current. Galvanic cell reactions supply energy, which is used to perform work. For this reason, galvanic cells are commonly used as batteries.  A galvanic cell consists of at least two half cells, a reduction cell and an oxidation cell. Chemical reactions in the two half cells provide the energy for the galvanic cell operations.

electrolyte
it’s a liquid, gelatinous or solid material that contains ions. In a battery, the electrolyte is the material that allows electricity to flow from one plate to another (between positive and negative electrodes

Electroplating
Electroplating is the process of coating a metal on the surface of a conductor by electrolysis. It’s is an art of protecting metal surface form corrosion and giving it pleasant appearance. It’s apart from improving aesthetics of metals also brings about change in its physical, chemical and mechanical properties. It has wide range of applications starting from protection to many industrial uses.