<Tr> <Td> 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 m or 6990100000000000000 ♠ 100 pm). </Td> </Tr> <Tr> <Th> Classification </Th> </Tr> <Tr> <Td> <Table> <Tr> <Td> Smallest recognized division of a chemical element </Td> </Tr> </Table> </Td> </Tr> <Table> <Tr> <Td> Smallest recognized division of a chemical element </Td> </Tr> </Table>

What are the physical properties of an atom