Question

Two alpha particles are emitted from an element whose mass number is $226$ and the atomic number of the element obtained after emission?

Answer 1

Alpha decay is defined as the loss of an alpha particle which is a helium atom from an unstable nucleus. Given that the element with mass number $226$ undergoes decay to form two alpha particles. Thus, the element formed after decay has the mass number $218$ with atomic number $84$ and the chemical element is polonium.

Complete Step By Step Answer:
Some chemical elements which can exist as isotopes are unstable and undergo radioactive decay or decomposition to form a stable nucleus and the process is known as decay. There are different types of decay like alpha decay and beta decay.
Alpha decay is defined as the decay in which the alpha particles come out from the unstable nucleus.
Given that two alpha particles are emitted from an element whose mass number is $226$
The element with mass number $226$ is radium with atomic number $88$ It undergoes alpha decay as follows:
$_{88}^{226}Ra \to _2^4He + _{86}^{222}Rn$
Now the element radon is formed with mass number $222$ with atomic number $86$ and undergoes alpha decay as follows:
$_{86}^{222}Rn \to _2^4He + _{84}^{218}Po$
Thus, after emission of two alpha particles from an element whose mass number is $226$ is the polonium element.

Note:
Alpha particle means helium element with atomic number $2$ and mass number $4$ . Given that two alpha particles were emitted. Thus, the element obtained is polonium. But polonium is not a stable nucleus with mass number $222$ the decay continues to form a stable nucleus like lead after a further number of decays.