How many of the following metal ions have similar value of spin only magnetic moment in gaseous state? $\_\_\_\_$
(Given: Atomic number : V, $23 ; \mathrm{Cr}, 24 ; \mathrm{Fe}, 26 ; \mathrm{Ni}, 28$ ) $\mathrm{V}^{3+} \cdot \mathrm{Cr}^{3+}, \mathrm{Fe}^{2+}, \mathrm{Ni}^{3+}$
