Successive emission of an $\alpha$-particle and two $\beta$-particles by an atom of an element results in the formation of its

Which of the following pairs of nuclides is an example of isotones?

The isotope that causes skin disease is

Which radioactive carbon isotope has been helpful in understanding the mechanism of photosynthesis in plants?

In the following radioactive transformation given below $R$ $\xrightarrow{\alpha} X$ $\xrightarrow{\beta} Y$ $\xrightarrow{\beta} Z$; the nuclei $R$ and $Z$ are

Which among the following isotopes is not found in natural uranium?