Volcanoes and deep sea hydrothermal vents are both associated with sulfur-rich environments. Mount Etna is classed as a continuously degassing volcano and emissions of SO₂ and H₂S are around 1.5 Tg y⁻¹ and 100 Gg y⁻¹, respectively (Tg = 10¹² g; Gg = 10⁹ g). 

(a) Draw Lewis structures for H₂S and SO₂, ensuring that the octet rule is obeyed by the S and O atoms. Your answer must be consistent with the fact that in SO₂, the two sulfur–oxygen bonds are the same length. 

(b) Are H₂S and SO₂ polar or non-polar molecules? If polar, draw a diagram to show the direction of the molecular dipole moment.

(c) In the troposphere, SO₂ reacts with HO^· radicals. Construct an MO diagram for HO^· from H and O atoms, and deduce what you can about the bonding in HO^·.