Question

what is the missing particle?

190/78 pt → 4/2 he + ?

186/76 pt 186/76 os 194/80 hg

Explanation:

Step1: Calculate the mass number

The mass number of the reactant is \(190\), and the mass number of \(\ce{^{4}_{2}He}\) is \(4\). Let the mass number of the missing particle be \(A\). According to the conservation of mass number \(A = 190-4=186\).

Step2: Calculate the atomic number

The atomic number of the reactant (\(\ce{Pt}\)) is \(78\), and the atomic number of \(\ce{^{4}_{2}He}\) is \(2\). Let the atomic number of the missing particle be \(Z\). According to the conservation of atomic number \(Z=78 - 2=76\).

Step3: Identify the element

Looking at the periodic table, the element with atomic number \(76\) is Osmium (\(\ce{Os}\)).

Answer:

\(\ce{^{186}_{76}Os}\)