1. What element has 81 protons in the nuclei of its atoms?

A. Platinum

B. Lead

C. Thallium

D. Uranium

A little trick i learnt: The atomic number reflects how many electrons there are, and there must be an equal charge. therefore, there are the same amount of protons as there are electrons. so if it has 81 protons, we look for number 81 in the periodic table, Thallium