परमाणु (Atom) कउनो तत्व के सबसे छोट भाग ह जेमें उ तत्व के रासायनिक गुण निहित होखेला।
Helium atom
Helium atom ground state.
An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. The black bar is one angstrom (6990100000000000000♠10−10 m or 6990100000000000000♠100 pm).