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 .

## Chemical Laws

### **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 .