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

The smallest particle of an element that can exist independently is called an atom. It is the fundamental unit of matter and often referred to as the basic building block of chemistry. The concept of the atom was first proposed by Democritus nearly 2500 years ago.

All forms of matter—solids, liquids, gases, and plasma—are made of atoms, either neutral or ionized. Atoms combine to form molecules, which further interact to create different states of matter. Atoms are extremely tiny, about 100 picometers in size, and all atoms are nearly similar in scale.

An atom consists of a nucleus surrounded by a cloud of negatively charged electrons. The nucleus contains positively charged protons and neutral neutrons. Most of the atom’s volume is empty space, while nearly all of its mass is concentrated in the nucleus.

The atomic number of an element is defined by the number of protons in its nucleus, and this number is unique for every element.