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

State whether the following statements are true or false:
$(i)$ Isobars have different atomic numbers.
$(ii)$ $_{14}^{30}\text{Si}$,$_{16}^{32}\text{S}$ are isotones.
$(iii)$ Niels Bohr was the first to suggest that the atom is spherical.
$(iv)$ Rutherford's model is accepted as the nuclear model of the atom.

The electronic configuration of a divalent metal ion $M^{2+}$ is $2, 8, 14$ and its atomic mass is $58 \, a.m.u.$ What is the number of neutrons in its nucleus?

Which of the following species are isoelectronic (i.e.,have the same number of electrons)?
$Na^{+}, K^{+}, Mg^{2+}, Ca^{2+}, S^{2-}, Ar$

Calculate the number of electrons,protons,and neutrons in $Cl_{2}$,$Cl$,and $Cl^{-}$. (Given for $Cl$: $Z = 17$ and $A = 35$)

Which of the following species does not have the same number of electrons as the other three species?