Final answer:
The complete alpha decay equation for (²²⁶Ra) is (²²⁶Ra → ²²²Rn + ⁴He). Therefore the correct option is (a) (²²⁶Ra → ²²²Rn + ⁴He).
Step-by-step explanation:
The correct complete alpha decay equation for (²²⁶Ra) is (²²⁶Ra → ²²²Rn + ⁴He) as given in option (a). In this decay, a helium-4 nucleus (⁴He) is emitted from the radium-226 nucleus, resulting in the formation of radon-222 (²²²Rn) as the daughter nucleus.
During alpha decay, a nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons.
This results in the original atom losing four units of mass and two units of atomic number, as reflected in this decay equation where Radon-222 (222Rn) is produced along with an alpha particle, represented as Helium-4 (4He).