Input interpretation
sulfite anion
Lewis structure
Draw the Lewis structure of sulfite anion. Start by drawing the overall structure of the molecule, ignoring potential double and triple bonds: Count the total valence electrons of the oxygen (n_O, val = 6) and sulfur (n_S, val = 6) atoms, including the net charge: 3 n_O, val + n_S, val - n_charge = 26 Calculate the number of electrons needed to completely fill the valence shells for oxygen (n_O, full = 8) and sulfur (n_S, full = 8): 3 n_O, full + n_S, full = 32 Subtracting these two numbers shows that 32 - 26 = 6 bonding electrons are needed. Each bond has two electrons, so we expect that the above diagram has all the necessary bonds. However, to minimize formal charge oxygen wants 2 bonds. Identify the atoms that want additional bonds and the number of electrons remaining on each atom. The net charge has been given to the most electronegative atom, oxygen, in 2 places: In order to minimize their formal charge, atoms with large electronegativities can force atoms with smaller electronegativities on period 3 or higher to expand their valence shells. The electronegativities of the atoms are 2.58 (sulfur) and 3.44 (oxygen). Because the electronegativity of sulfur is smaller than the electronegativity of oxygen, expand the valence shell of sulfur to 4 bonds. Therefore we add a total of 1 bond to the diagram, noting the formal charges of the atoms. Double bonding sulfur to the other highlighted oxygen atoms would result in an equivalent molecule: Answer: | |
General properties
formula | (SO_3)^(2-) net ionic charge | -2 alternate names | trioxosulfate | trioxidosulfate | sulfite | sulfite(2-)
Other properties
ion class | anions | oxoanions | polyatomic ions common sources of ion | zinc sulfite dihydrate (1 eq) | silver(I) sulfite (1 eq) | potassium sulfite (1 eq)
Thermodynamic properties
molar free energy of formation Δ_fG° | aqueous | -486.5 kJ/mol (kilojoules per mole) molar heat of formation Δ_fH° | aqueous | -635.5 kJ/mol (kilojoules per mole) molar entropy S° | aqueous | -29 J/(mol K) (joules per mole kelvin)