Briefly describe the following terminologies:
1. Chemical changes
The changes that occurs in the structure and composition of the matter is known as the chemical change. It is irresible and one directional.
2. Compound
The chemical substance that is formed by the composition of two or more than two elements combined in fixed proportion. It is result of the chemical change between the elements.
3. Element
Element is the purest form of matter that can neither be created nor can be destroyed.

4. Atomic Number
The number of electron or the number of protons in aen electrically neutral atom is known as the atomic Number. It is usully denoted by A. It is typical number that helps to determine the chemical and physical properties of an atom.
In an neutral atom,
Atomic Number(A)= Number of electron= Number of the Proton
5. Mass Number
Mass number of an atom is the sum of the mass of the sub-atomic particle of an atom, particularly neutron and electron ( the mass of electron is negligible). Thus, mass number is the mass of the nucleus of an atom.
It is usually denoted by the letter Z.
Mass Number= Mass of Proton+ Mass of Neutron
6. Isotopes
Isotopes are the different form of the elements with atomic number but different mass number. It usually differ in the number of the neutrons.
Example, Chlorine-36 and Chlorine-37 are Isotopes.
7. Mole
Mole is the quantity of any matter that contain the Avagardo number of it.
Avogadro Number= 6.023*10^23
For example: 1 mole of Carbon atom=