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

A. Platinum

B. Lead

C. Uranium

D. Thallium

The question asks us to choose the element which has 81 protons in the nuclei of its atoms. We can use Periodic system of elements. There we can see that TL is an element with the atomic number 81. Thallium (Tl) is a toxic metal. it has : 81 electrons, 81 protons and 123 Neutrons. Answer: D. Thallium.

The element that contains 81 protons in the nuclei is Thallium. The answer to this item is letter D. The number of protons in the nuclei of the remaining choices are 78, 82, and 92 for Platinum, Lead, and Uranium, respectively. If an atom is neutral, this means that the number of proton is equal to the number of electrons.