In chemistry, resonance or mesomerism is a way of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by one single Lewis structure.Contributing structures differ only in the position of electrons, not in the position of nuclei.

Electrons have no fixed position in atoms, compounds and molecules , but have probabilities of being found in certain spaces (orbitals). Resonance forms illustrate areas of higher probabilities (electron densities). The term Resonance is applied when  there are two or more possibilities available. Resonance structures do not change the relative positions of the atoms For a compound to show resonating structures , it should

1) have a planar structure

2) follow Hackel's rule of electron numbers

3) hybridization remains same and fixed

4) no of lone pairs remain same .

The limiting reagent (or limiting reactant) in a chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by this reagent, since the reaction cannot continue without it.

A molecule will be stable if there are more attractive forces and less repulsive forces.

Attractive forces lower the potential energy of the molecule and repulsive forces increase the potential energy of the molecule.

Therefore molecules with lower energy are more stable.

This is used in energy minimization to determine the most stable conformation of a molecule, most stable structure of a molecule etc.

It is also used in binding studies to determine the most stable interaction between a substrate/ligand/drug and the enzyme.

Entropy is property where as enthalpy is energy.

Entropy is function of quantity of heat, the property of the system which decides the percentage of heat that can be converted into work. Entropy shows the randomness of molecules.If the randomness of molecules is more, then the increase in entropy in a process will be more, hence the percentage of heat that can be converted into work will be less. In other words, entropy is a function of quantity of heat.

Enthalpy is energy, the sum of internal energy and flow energy is called as enthalpy.

The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today.The Haber Process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The reaction is reversible and the production of ammonia is exothermic. The catalyst is actually slightly more complicated than pure iron.

The second electron is added to the negatively charged oxygen atom and therefore more electron-electron repulsion. To overcome this repulsion energy has be supplied and hence it is positive.

J.J.Thomson

The particle that J.J.Thomson discovered in 1897, the electron.

j.j. thomson.

An acyl halide (also known as an acid halide) is a chemical compound derived from an oxyacid by replacing a hydroxyl group with a halide group.

If the acid is a carboxylic acid, the compound contains a –COX functional group, which consists of a carbonyl group singly bonded to a halogen atom. The general formula for such an acyl halide can be written RCOX, where R may be, for example, an alkyl group, CO is the carbonyl group, and X represents the halide, such as chloride. Acyl chlorides are the most commonly encountered acyl halides, but acetyl iodide is the one produced (transiently) on the largest scale. Billions of kilograms are generated annually in the production of acetic acid.

P (1s² 2s² 3s² 3p⁶) is able to expand its valency to 5 due to the presence of empty d orbitals and forms PCl₅. Nitrogen doesent have ant empty d orbiatls, so it can have a maximum valency of 3.

Electromagnetic radiation (EMR) is a kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously. It consists of self-sustaining oscillating electric and magnetic fields at right angles to each other and to the direction of propagation. EMR does not require a supporting medium and travels through empty space at the speed of light.

Electromagnetic radiation (EMR) is a kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously. It consists of self-sustaining oscillating electric and magnetic fields at right angles to each other and to the direction of propagation. EMR does not require a supporting medium and travels through empty space at the speed of light