Draw a Lewis structure for each molecule and determine its molecular geometry. What kind of intermolecular forces are present in each substance?
(a)Lewis structure of H2Se:angular geometry
Hydrogen selenide is an inorganic compound with the formula H₂Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H₂Se is a colorless, flammable gas under standard conditions.
It is a selenium atom with two bonds to hydrogen atoms and two lone pairs. There is a definite polar bond here: Selenium is more electronegative than hydrogen so electrons will tend to go towards the selenium atom, causing a dipole. However, it is not polar enough to be considered a hydrogen bond. The answer is that dipole-dipole causes most of the intermolecular forces (although london dispersion forces always exist. It's just in this case they are insignificant compared to dipole-dipole).
(b)Lewis structure of SO2 :angular geometry
Sulfur dioxide is the chemical compound with the formula SO 2. At standard atmosphere, it is a toxic gas with a pungent, irritating smell. The triple point is 197.69 K and 1.67 kPa. It is released naturally by volcanic activity
Dipole-dipole forces occur when polar molecules are attracted to one another due the attraction of opposite charges. Polar molecules have partial negative charge on the more electronegative atom and partial positive charge on the less electronegative atom because the more electronegative one pulls electrons from the other. The partial charges on adjacent molecules is the dipole-dipole force.
In this case, sulfur dioxide is polar because oxygen is more electronegative than sulfur. However, way more important than this is the fact that there is a partial negative charge on both oxygen atoms (see the diagram) and a partial positive charge on sulfur (see diagram), making this an extremely polar molecule.