Question

what is the missing particle?

198 86 rn → 194 84 po + ?

Explanation:

Step1: Calculate the mass number of the missing particle

The mass number of \(^{198}_{86}Rn\) is \(198\), and the mass number of \(^{194}_{84}Po\) is \(194\).
Let the mass number of the missing particle be \(A\). According to the conservation of mass number in nuclear reactions \(A = 198-194=4\).

Step2: Calculate the atomic number of the missing particle

The atomic number of \(^{198}_{86}Rn\) is \(86\), and the atomic number of \(^{194}_{84}Po\) is \(84\).
Let the atomic number of the missing particle be \(Z\). According to the conservation of atomic number in nuclear reactions \(Z=86 - 84=2\).

Step3: Determine the element of the missing particle

The element with atomic number \(Z = 2\) is Helium (\(He\)).

Answer:

\(^{4}_{2}He\) (the first option in the given choices)