Identify the element having lowest first ionization enthalpy.

Calculate molar mass of an element having density $8.6 \mathrm{~g} \mathrm{~cm}^{-3}$ if it forms bec structure $\left[\mathrm{a}^3 \times \mathrm{N}_{\mathrm{A}}=22.0 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right]$

Which from following mixtures in water acts as a basic buffer?

Which from following molecules does not have lone pair of electrons in valence shell of central atom?