Atomic structure is the structure of an atom in a chemical element.
An atom consists of a nucleus of the size of 1/1000th of the atom at its center. In the nucleus there are particles called neutrons and protons. The neutrons are neutral in electrical charge and have a mass nearly equal to that of protons.
The protons have an electric charge of 1.6 * 10^-19 C and have mass nearly thousand times that of electrons. Electrons have a mass of 10^-31 kg.
The electrons are negatively charged particles which orbit around the nucleus in fixed orbits. The electrons are bound to the nucleus due to electrical attraction. The number of electrons in an atom of a neutral element is same as that of protons.
The atom looks like an electron cloud with many electrons in their smaller and bigger orbits moving so fast as 1,000 km/sec.
The properties of matter (element or substance) is the result of the number of electrons, neutrons, protons, and the configuration of electrons, size of atom and size of nucleus.
Further, it is said that protons and neutrons are made of subatomic particles called quarks.
The structure of an atom is same for all atoms of the same chemical element, having the same composition. The size of an atom increases with the atomic number of the element.