Which element from the following forms colourless compounds in $+2$ oxidation state?

An atom with atomic number $21$ belongs to the category of

In chromyl chloride,the number of $d$-electrons present on chromium is same as in (Given atomic number of $Ti = 22, V = 23, Cr = 24, Mn = 25, Fe = 26$)

Misch metal is an alloy of $:-$

Which of the following species would be expected to be paramagnetic?

Calculate the number of unpaired electrons in the following gaseous ions: $Mn^{3+}, Cr^{3+}, V^{3+}$ and $Ti^{3+}$. Which one of these is the most stable in aqueous solution?