$_{18}Ar^{40}$,$_{20}Ca^{40}$ and $_{19}K^{40}$ are

The nuclides (a nuclide is the general name for any nuclear species) $_6C^{12}$,$_{26}Fe^{56}$,and $_{92}U^{238}$ have $12$,$56$,and $238$ nucleons respectively in their nuclei. The total number of nucleons in a nucleus is equal to:

The phosphide ion has an electronic structure similar to that of:

Which of the following properties are different for neutral atoms of isotopes of the same element?

Give the symbol of the following species:
$(i)$ Number of electrons,protons,and neutrons are $10, 8$,and $8$ respectively.
$(ii)$ $Ca$ $(Z = 20)$ and nucleon number $= 40$.
$(iii)$ Species with mass number $25$,protons $12$ (magnesium),and electrons $10$.
$(iv)$ Species of Bromine in which $(Z = 35)$,electrons $36$,and neutrons $45$.
$(v)$ $+2$ positive and $-2$ negative ions that are isoelectronic with $Al^{3+}$ $(Z = 13)$.

Which of the following pairs represents an iso-electronic species?