Question

multiple choice 1 point
what is the missing element in this equation. you may use the periodic table to help you
210 84?→206 82pb+4 2he
multiple choice 1 point
for the following equation, what is the mass of the missing element?
235 92u+1 0n→95 37rb+□+2.1 0n
po pt pm pz

Explanation:

Step1: Balance atomic number

In nuclear reactions, the sum of atomic numbers on the left - hand side equals the sum on the right - hand side.
The atomic number of \(U\) (\(Z = 92\)), the atomic number of \(n\) (\(Z = 0\)), the atomic number of \(Rb\) (\(Z = 37\)), and the atomic number of \(He\) (\(Z = 2\)).
For the first reaction: \(92+0 = 37+Z + 2\times0\). Solving for \(Z\): \(Z=92 - 37=55\).
For the second reaction: Let the atomic number of the unknown element be \(Z\). We know that in \(_{84}^{210}?\to_{82}^{206}Pb + _{2}^{4}He\), using the atomic number balance \(Z=82 + 2=84\).

Step2: Balance mass number

For the first reaction: The mass number of \(U\) (\(A = 235\)), the mass number of \(n\) (\(A = 1\)), the mass number of \(Rb\) (\(A = 95\)), and the mass number of \(n\) (\(A = 1\)).
\(235 + 1=95+A+1 + 2\times1\). Solving for \(A\): \(A=236-(95 + 1+ 2)=138\). But this is not relevant for the second - type problem (finding the element symbol from atomic number).
For the second reaction: Using mass number balance \(A = 206+4=210\). The element with atomic number \(Z = 84\) is \(Po\) (Polonium).

Answer:

Po