Question

The symbols given below represents the nuclei of radioactive elements. Which among the following are isotopes?

${}_{91}^{230}W$, ${}_{92}^{235}X$, ${}_{93}^{238}Y$, ${}_{92}^{238}Z$

Answer 1

Isotopes are the atoms of same element having the same atomic number but different mass number.

As the nuclei ${}_{92}^{235}X$ and ${}_{92}^{238}Z$ have the same atomic number 92 but different atomic masses 235 and 238 respectively therefore they are isotopes.