An isotope of oxygen has a mass number of $18$. Other isotopes of oxygen will have the same:

The expression $Ze$ gives :

If the atomic weight of an element is $23$ times that of the lightest element and it has $11$ protons,then it contains

Consider an imaginary ion ${}_{22}^{48}X^{3-}$. The nucleus contains '$a$'$\%$ more neutrons than the number of electrons in the ion. The value of '$a$' is $.....$ [nearest integer].

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

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.