Bohr, Niels (1885-1962), was a noted Danish physicist who developed a theory about the structure of the atom. Bohr's theory, published in 1913, was based on an earlier one proposed by Ernest Rutherford, a New Zealand-born physicist. Rutherford had shown that the atom consisted of an extremely small, positively charged nucleus, with negatively charged electrons whirling around the nucleus. Bohr proposed that the electrons could travel only in certain successively larger orbits around the nucleus. He thought the outer orbits could hold more electrons than the inner ones. Bohr also suggested that the electrons in the outermost orbit determined the atom's chemical properties.