JSIERT

The atoms of different elements with the same mass number, but different atomic number.

The atmos of the same element having the same atomic number but different mass number.

Atoms of all noble gases have eight electron in their outermost shell. This arrangement is known as Octet.

Valency of an element is the combining capacity of that element with other elements and is equal to the number of electrons that take part in a chemical reaction.

Those elements that can gain electrons to form ions which are negatively charged are called Anions.

Those elements that can lose electrons to form ions which are positively charged are called Cations.

The electrons present in the valence shell are known as Valence electron .

The outermest shell of an atom is called its Valence shell.

Mass number of an element is the total number of protons and neutrons present in the nucleus.

Atomic number is equal to the number of electrons in the neutral atom of an element .