is atom a solid?since it is unbreakabledont say me that it is that which constitutes a matter

The name atom comes from the Greek átomos, which means uncuttable, something that cannot be divided further. The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.

Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton and the neutron. However, the hydrogen-1 atom has no neutrons and a positive hydrogen ion has no electrons.

Even electrons and protons are not indivisible. New theories suggets that even electrons and protons are composed od even smaller particles called "quarks". 

Don't think of these tiny particles as "solid". Solids are defined only in the macroscopic word, not in the microscopic world. Even liquids and gases are made up of atoms. Just understand that the microscopic world is very very different from the outside world. So the usual picture of the atom being a solid ball doesn't work here.