Write a symbol for each of the following neutral isotopes.

Write a symbol for each of the following neutral isotopes. Include the atomic number and mass number for each.
(a) the chalcogen with a mass number of 125?
(b) the halogen whose longest-lived isotope is radioactive?
(c) the noble gas, used in lighting, with 10 electrons and 10 neutrons?
(d) the lightest alkali metal with three neutrons?