How many protons and neutrons does thorium have?
90 protons, 90 electrons
Th-232 isotope has 142 neutrons
Thorium has an atomic number of 90, or in other words, 90 protons in its nucleus. The mass number or the identification of the -232 isotope with its 142 neutrons is a red herring - in isotopy the number of neutrons may vary but the atomic number or the count of protons is the same. If the atomic number varied from 90 it would by definition no longer be thorium.