The oxoanion in which the oxidation state of the central atom is same as its group number in the periodic table is

$FeSO_4 \cdot 7H_2O$ (Green Vitriol) salt on thermal decomposition does not produce

For $Cu_{2}Cl_{2}$ and $CuCl_{2}$ in aqueous medium,which of the following statements is correct?

Choose the correct statements from the following:
$A$. $Mn_2O_7$ is an oil at room temperature.
$B$. $V_2O_4$ reacts with acid to give $VO^{2+}$ ions.
$C$. $CrO$ is a basic oxide.
$D$. $V_2O_5$ does not react with acid.
Choose the correct answer from the options given below:

When potassium permanganate $(KMnO_4)$ is heated at $513 \ K$,it decomposes to form two manganese-based products. The physical properties of the product in which manganese has a higher oxidation state than the other are:

$A$ first row transition metal with the highest enthalpy of atomization,upon reaction with oxygen at high temperature,forms oxides of the formula $M_2O_n$ (where $n=3, 4, 5$). The 'spin-only' magnetic moment value of the amphoteric oxide from the above oxides is $......$ $BM$ (nearest integer). (Given atomic number: $Sc: 21, Ti: 22, V: 23, Cr: 24, Mn: 25, Fe: 26, Co: 27, Ni: 28, Cu: 29, Zn: 30$)