Basic Chemistry

Atoms
An atom is the smallest, indivisible part of a substance.

Electrons
Electron is a Negatively charged fundamental Particle, which revolves around the nucleus around a fixed stationary energy level orbit.

Protons
Proton is a Positively Charged Fundamental Particle, which is present in the nucleus.

Neutrons
Neutron is a Neutral Fundamental Particle, present in the Nucleus

Others
Positron, Quark , Neutrinos , Boson , Fermion , Leptons , etc.

Atomic Number
Atomic Number is the number of Electrons or Protons present in the Atom.

Atomic Mass Number
Atomic Mass is the sum total of the number of Protons and Neutrons (nucleons) in an atom. Atommic Mass Number is represented in terms of Unified Mass Unit which is equal to the mass of 1/12th of C12 atom (1 proton).

Mass of Proton   =  1.6 x 10-24 g

Mass of Electron =  9.1 x 10-28 g

Mass of Neutron = 1.6 x 10-24 g

Isotopes
Atoms having the same atomic number, but different atomic masses are called as Isotopes.

Isobars
Atoms having the same atomic mass, but different atomic numbers are called as Isobars.

Elements
The fundamental, independent particles , which can be represented by a single atom are called as elements.

Metals & Non Metals
Electron Donating Species are called as Metals & Electron Withdrawing species are called as Non-Metals.

Molecules
A collection of atoms bonded together, is called as a molecule.

Compounds
A Compound is a molecule consisting of 2 or more atoms in its structure.

Chemical Reactions
A Chemical Reaction occurs when a Chemical Change occurs. Reactants react with each other under certain conditions with the help of catalysts to form products.

Law of Conservation of Mass
Law of Conservation of Mass states that mass is neither created nor destroyed in a Chemical Reaction. It is only converted from reactants to products.

Law of Constant Proportions
The Law of Constant Proportions states that if a pure sample of a compound is formed by two reacting molecules, they will do so in a fixed ratio of their masses , independent of their source.

Law of Multiple Proportions
The Law of Multiple proportions states that when two elements combine to form two or more products, the ratio of their masses is always the same or a whole number ratio of each other.

Law of Reciprocal Proportions
The Law of Reciprocal Proportions states that if two different elements are combining with a third element, then the ratio in which they combine is either the same or a simple whole number ratio of proportion in which they combine with each other.

Molecular Formula
The Symbolic representation of a molecule or compound, so as to show the number of atoms of a particular element in the molecule is called as molecular formula.

Empirical Formula
The simplest ratio of a molecular formula is the

Percentage Composition
If the mass percentage is less than 100, then the rest of the compound consists of Oxygen.

The percentage composition consists of the percentage of mass occupied by each element in the molecule.

Limiting and Excess Reagents
Limiting reagents are taken in a limited quantity, while excess reagents are taken in excessive quantity.

Stoichiometry
Calculations based on mass - mass relation, volume - mass relation and volume - volume relation is called as Stoichiometry.

The coefficients or number of moles obtained after balancing the reaction are called as stoichiometric coefficients.