Answer:
[tex]Bismuth-210\text{ -}__{_{83}}^{210}Bi[/tex]
Explanations:
If the atom of Astatine-214 undergo alpha particle, it will emit helium element as shown;
[tex]_{85}^{214}At\rightarrow_{83}^{210}Bi+_2^4He[/tex]
According to the decay, 4 is subtracted from the mass number and 2 from the atomic number.
According to the reaction, the new isotope produced is Bismuth-210
