ATOMIC STRUCTURE

There are 118 elements identified worldwide so far. Out of these elements, elements occur in the nature and the remaining elements are synthesised in the laboratories.

Copper, Iron, Gold and Silver are some of the elements found in the .

Elements like Technetium, Promethium, Neptunium and Plutonium are synthesised in the .

provided a basic theory about the nature of matter. He proposed a model of atom known as Dalton’s atomic theory in 1808

All the matters are made up of extremely small particles called

Dalton’s theory explains most of the properties of gases and

Dalton’s theory helps to recognize the molecular differences of elements and .

Atoms of the same element have different

The electrode which is connected to the negative terminal of the battery is called the

The electrode connected to the positive terminal is called the

Cathode rays travel in line from cathode towards anode.

Cathode rays are deflected by both and magnetic fields.

When invisible radiation falls on materials like zinc sulphide, they emit a visible light. These materials are called materials.

Anode rays travel in lines

When hydrogen gas was taken in a discharge tube, the positively charged particles obtained from the hydrogen gas were called

Neutron is a neutral particle, that is, it carries

Protons and neutrons are found at the centre of an atom, called .

Electrons are revolving around the nucleus in a circular path, called .

The electrons revolving in the outermost orbit are called .

The arrangement of electrons in the orbits is known as .

is defined as the number of electrons lost, gained or shared by an atom in a chemical combination

Generally, valency of an atom is determined with respect to hydrogen, oxygen and chlorine.

ATOMIC STRUCTURE

Gap-fill exercise