How is matter constituted or formed?

Solution:

The same as a building is made of building units called bricks and blocks, matter is made of building units called atoms and molecules.

An atom is the smallest part of an element that can exist chemically. Up to now (2020), 118 chemical elements have been discovered. Atom of each element is represented by a symbol that is unique and identifies it. Some atoms are represented by one letter symbol written always as capital letter. Example: an atom of Hydrogen (H), Oxygen (O), Fluorine (F).

Other elements are represented by a 2 letters symbol, where the first letter is always a capital letter, whereas the second is always a small letter. Example: Atom of Sodium (Na), Helium (He), Calcium (Ca).

Some chemical symbols originate from former Latin names such as Fe (from Ferrum) for Iron, Na (from Natrium) for Sodium.

The molecule is a unit made of a combination of 2 or more atoms; it is the fundamental unit that forms chemical substances other than the rare gases. It is the smallest part of a chemical substance that can take part in a chemical reaction. Example: Molecule of Hydrogen (H2), Water (H2O), Sulphuric acid (H2SO4).