sentences: atomic number is used to describe the proton number of an element
docs: atomic_nucleus is microscopic_object. atoms has electrons decimal is number. hydrogen has atomic_number_of_one atomic_number is positive_integer. atomic_ion is atom. atomic_number is number. hydrogen_maser_atomic_clock is atomic_clock. each_element_in_periodic_table has number_associated_with magic_number is atomic_number.