Question

what is the missing particle?

226 88 ra → 4 2 he + ?

222 86 rn

222 86 ra

224 86 rn

Explanation:

Step1: Calculate mass number

Mass number of Ra is \(226\), mass number of He is \(4\). So mass number of missing particle is \(226 - 4=222\).

Step2: Calculate atomic number

Atomic number of Ra is \(88\), atomic number of He is \(2\). So atomic number of missing particle is \(88 - 2 = 86\).

Step3: Identify element

Element with atomic number \(86\) is Rn (Radon).

Answer:

\(\ce{^{222}_{86}Rn}\)