Question

What is the smallest particle of an element that can exist called?

Answer 1

Hint: Atom is the smallest particle of every element. They are called the building block in chemistry. They are extremely small in size. They cannot be seen by naked eyes. They are present deep inside every element. It contains protons, neutrons and electrons.

Complete answer:
The smallest particle of an element that can exist is called an atom. It is the smallest unit of every element. It is also called the basic building block of chemistry. The idea of the atom was first introduced by Democritus, almost $2500$ years ago.
Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms combine to form molecules, which then interact to form solids, gases, or liquids. These are extremely small particles typically around $100$ picometers approx. All atoms are roughly the same size. Every atom is composed of a nucleus surrounded by a cloud of negatively charged electrons. The nucleus is made of one or more positively charged protons and several neutrons. Most spaces in the atom are empty spaces and the rest space is occupied by protons, neutrons, and electrons. Despite the small size of the nucleus, virtually all the mass of the atom is concentrated there. The atomic number is the number of protons an atom has. It is characteristic and unique for each element.

Note:
Whenever there is an addition of an atom then there is the formation of a new element, and whenever there is the addition of a neutron, there is the formation of an isotope or a heavier version of that particular atom. Atoms have different properties based on the arrangement and number of their basic particles.