Compared with an atom of atomic weight $12$ and atomic number $6$,the atom of atomic weight $13$ and atomic number $6$:

Give the relation between the following pairs of species:
$(i)$ $_{20}^{40}Ca$ and $_{19}^{40}K$
$(ii)$ $_{17}^{35}Cl$ and $_{17}^{37}Cl$
$(iii)$ $_{18}^{40}Ar$,$_{20}^{40}Ca$ and $_{19}^{40}K$
$(iv)$ $_{38}^{87}Sr$ and $_{38}^{90}Sr$

Which of the following atoms or ions is isoelectronic with neon $(Ne)$?

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

Isotopes of an element have

$Ca$ has atomic number $20$ and atomic weight $40$. Which of the following statements is not correct about $Ca$ atom?