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).
Classification
Smallest recognized division of a chemical element
Properties
Mass range:
6973167000000000000♠1.67×10−27 to 6975452000000000000♠4.52×10−25 किg
