RUTHERFORD’S ATOMIC MODEL OR PLANETRY MODEL OF AN ATOM OR GOLD FOIL EXPERIMENT OR DISCOVERY OF NUCLEUS: In order to determine the structure of an atom, Rutherford carried out Gold Foil experiment in year 1911.He bombarded alpha-particles on 0.00004cm thick gold foil. Alpha-particles are emitted from radioactive elements like Radium and Polonium.

Discovery of Neutrons

In 1920 Rutherford predicted the existence of neutral particle in an atom. In 1932 James Chadwick bombarded alpha particles on the nucleus of beryllium. It produced neutral particles having mass equal to proton and carry no charge. These particles were named as neutrons.

Discovery of Protons

DISCOVERY OF PROTON OR DISCOVERY OF CANAL RAYS: In 1886, GOLDSTEIN observed that in addition to cathode rays , other rays were also present in the discharge tube. These rays were travelling in opposite direction to cathode rays. He used a discharge tube having perforated cathode that is holes were present in cathode. He found […]

Cathode Rays Experiment and Discovery of Electrons

CATHODE RAYS EXPERIMENT: In 1895, Sir William Crooks performed experiments by passing electric current through gases in a discharge tube at a very low pressure. During this experiment crooks observed radiations , that were later named electrons.

State the reasons: soft drink is a mixture and water is a compound

Soft drink is formed by simple mixing of water, CO2 and sugar while water is formed by chemical combination of hydrogen and oxygen. Components of soft drink can be easily separated by physical means while components of water can not be separated by physical means. Components of soft drink has no fixed ratio by mass while […]

Why do you think air is a mixture and water a compound

Air is a mixture and water is a compound due to following reasons. 1) Air is formed by simple or physical mixing of different gases while water is formed by chemical combination of hydrogen and oxygen. 2) air does not have any chemical formula while water has chemical formula that is H2O.

Mole and Avogadro’s Number

Mole (Chemist secret unit) A mole is defined as the amount(mass) of a substance that contains 6.02 x 1023 number of particles (atoms, molecules or formula units). OR mole is the atomic mass, molecular mass or formula mass of a substance expressed in grams is called mole. It establishes a link between mass of a substance and number of particles. […]

Gram Atom, Gram Molecule and Gram Formula

1) Gram Atomic Mass: The atomic mass of an element expressed in grams is called gram atomic mass or gram atom. It is also called a mole. 1 gram atom of hydrogen = 1.008 g = 1 mol of hydrogen 1 gram atom of carbon = 12.0 g = 1mol of carbon It means that […]

Types of Molecule

Molecule: The smallest component of a substance (an element or a compound) that can exist independently or freely in nature is called a molecule. A molecule is  mostly formed by the chemical combination of atoms. It is the smallest unit of a substance. It shows all the properties of the substance and can exist independently.

Ion vs Free Radical

Differences between ion and free radical   Ions Free Radicals 1. These are the atoms which bear some charge. These are the atoms that have odd number of electrons. 2. They exist in solution or in crystal lattice. They can exist in solutions as well in air. 3. Their formation is not affected by the […]

Molecule vs Molecular Ion

Differences between molecule and molecular ion.   Molecule Molecular Ion 1. It is the smallest particle of an element or compound which can exist independently and shows all the properties of that compound. It is the formed by gain or loss of electrons by a molecule. 2. it is always neutral. It have negative or […]

Atom vs Ion

Differences between atom and ion.   Atom Ion 1. It is the smallest particle of an element. It is the smallest unit of an ionic compound. 2. it can or cannot exist independently and can take part in a chemical reaction. It cannot exist independently and is surrounded by oppositely charged ions. 3. it is […]

Cleavage in Chemistry

Cleavage: The splitting or breakage of the bond between two atoms due to absorption of heat or light energy is called cleavage. Types of cleavage: there are two types of cleavage.

Chemical species – Ion, Free Radical and Their Types

Chemical species: Atom or group of atoms which can take part in a chemical reaction or that is produced after a chemical reaction as a highly reactive substance is called chemical species. Types of chemical species: Following are the main types of chemical species. 1) ions  2) Free Radicals.

Molecular Mass and Formula Mass

Molecular Mass: The sum of atomic masses of all the atoms present in one molecule of a molecular substance, is its molecular mass. For example, molecular mass of chlorine (Cl2 ) is 71.0 amu, of water (H2O) is 18 amu and that of carbon oxide (CO2) is 44 amu.

How to Write Chemical Formula – Definition, Types and Significance of Formula

Chemical formula: The symbolic representation of all the elements(atoms) in the compound is called chemical formula. OR The way of representing of a molecule or a compound using the symbols of its elements. How to write a Chemical Formula: Compounds are represented by chemical formulae as elements are represented by symbols. Chemical formulae of compounds are written […]

Atomic Number, Mass Number, Relative Atomic Mass and amu

Atomic number or proton number or identification number: The number of protons present in the nucleus of an atom is called proton number or atomic number. Explanation: It is represented by symbol ‘Z’ . As all atoms of an element have the same number of protons in their nuclei, they have the same atomic number. […]

Atom – Short Note

Atom: (Derived from word atomos means indivisible but still atoms are divisible) smallest particle of an element which can take part in a chemical reaction is known as atom. Or The smallest building block of an element is called atom. Atoms of the same element are alike. For example gold element contain all gold atoms. Each […]

Mixture vs Compound

when two or more substances (elements or compounds) mix up physically without any fixed ratio by mass, they form a mixture. Mixture is of two types.   HOMOGENOUS MIXTURE: Mixtures that have uniform composition throughout are called homogeneous mixtures e.g. air, gasoline, ice cream.