Answer :
Final answer:
Thallium-210 (Tl-210) transforms into lead-210 (Pb-210) following beta decay, as this process increases the atomic number by one while keeping the mass number constant (option a).
Explanation:
When thallium-210 (Tl-210) undergoes beta decay, it is transformed into another element. During beta decay, a neutron in the nucleus is converted into a proton and emits an electron (beta particle) and an antineutrino. Since the number of protons in the nucleus determines the element, the addition of a proton during beta decay means that the atomic number increases by one. Accordingly, we can determine the new element by looking at the periodic table and finding the element that comes after thallium.
Thallium (Tl) has an atomic number of 81, so after emitting a beta particle, the nucleus will have 82 protons, making the element lead (Pb). As the mass number stays the same during beta decay (because a neutron changes into a proton), the resulting isotope is lead-210 (Pb-210).
The correct nuclear equation for the beta decay of thallium-210 is:
210Tl81 → 210Pb82 + e⁻ + v.
