Answer
a) ${^{16}O}$ and ${^{18}O}$, ${^{18}Ne}$ and ${^{20}Ne}$
b) ${^{18}O}$, ${^{18}F}$ and ${^{18}Ne}$
c) ${^{16}O}$ and ${^{18}O}$, ${^{18}Ne}$ and ${^{20}Ne}$
d) ${^{18}O}$ and ${^{20}Ne}$, ${^{16}O}$ and ${^{18}Ne}$
Work Step by Step
a) Atomic number of isotopes are same, but they differ in mass number. ${^{16}O}$ and ${^{18}O}$ have same atomic number, but differ in atomic mass. Hence they are isotopes and as is the case with ${^{18}Ne}$ and ${^{20}Ne}$.
b) Atoms of different elements having different atomic number but same mass number are called isobars. That is, ${^{18}O}$, ${^{18}F}$ and ${^{18}Ne}$ are isobars.
c) ${^{16}O}$ and ${^{18}O}$ will have the same chemical properties. Because atoms of the same element have the same chemical properties. Due to the same reason, ${^{18}Ne}$ and ${^{20}Ne}$ will also have the same chemical properties.
d) number of neutrons (n) = Mass number (A)-Atomic number (Z)
Using this formula, we find that ${^{18}O}$ and ${^{20}Ne}$ have the same number of neutrons. Similarly, ${^{16}O}$ and ${^{18}Ne}$ have the same number of neutrons.