Explain what the term isotope means.
A sulfur sample has these isotopic abundances by mass: isotope mass $32$, $33$, $34$ with percentage by mass $95.00\%$, $0.77\%$, $4.23\%$. Calculate the relative atomic mass, $A_r$, of sulfur to two decimal places.
Polonium isotopes, with proton number $84$, are formed through the radioactive decay of several elements, including thorium, Th, which has proton number $90$. The isotope $^{213}\text{Po}$ is formed from the thorium isotope $^{232}\text{Th}$. Complete the table to show the atomic structures of the isotopes $^{213}\text{Po}$ and $^{232}\text{Th}$ by giving the number of protons, neutrons and electrons.
In the first stage of the radioactive decay of $^{232}_{90}\text{Th}$, the products are an isotope of element $E$ and an alpha-particle, $^{4}_{2}\text{He}$. Using nucleon and proton numbers only, construct a balanced equation for the formation of the isotope of $E$ in this reaction: $^{232}_{90}\text{Th} \rightarrow \; \ldots \; + \; ^{4}_{2}\text{He}$. Show the nucleon number and proton number of the isotope of $E$ clearly.
Hence state the symbol for element $E$.