The number of elements present in the fourth period is

The electrode potentials for $Cu^{2+}_{(aq)} + e^- \to Cu^{+}_{(aq)}$ and $Cu^{+}_{(aq)} + e^- \to Cu_{(s)}$ are $+0.15 \ V$ and $+0.50 \ V$ respectively. The value of $E^\circ$ for the reaction $Cu^{2+}_{(aq)} + 2e^- \to Cu_{(s)}$ will be ............ $V$.

How many unit cells are present in $39 \ g$ of potassium that crystallises in body-centred cubic structure? [At. wt. of $K = 39$]

Which of the following statements is not valid for oxoacids of phosphorus?

If a polygon of $n$ sides has $275$ diagonals,then $n$ is equal to

The energy that should be added to an electron,to reduce its de-Broglie wavelength from $10^{-10} \ m$ to $0.5 \times 10^{-10} \ m$,will be