Input interpretation
carbonate anion
Lewis structure
Draw the Lewis structure of carbonate anion. Start by drawing the overall structure of the molecule, ignoring potential double and triple bonds: Count the total valence electrons of the carbon (n_C, val = 4) and oxygen (n_O, val = 6) atoms, including the net charge: n_C, val + 3 n_O, val - n_charge = 24 Calculate the number of electrons needed to completely fill the valence shells for carbon (n_C, full = 8) and oxygen (n_O, full = 8): n_C, full + 3 n_O, full = 32 Subtracting these two numbers shows that 32 - 24 = 8 bonding electrons are needed. Each bond has two electrons, so in addition to the 3 bonds already present in the diagram add 1 bond. To minimize formal charge oxygen wants 2 bonds and carbon wants 4 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: Fill in the 1 bond by pairing electrons between adjacent highlighted atoms, noting the formal charges of the atoms. Double bonding carbon to the other highlighted oxygen atoms would result in an equivalent molecule: Answer: | |
General properties
formula | (CO_3)^(2-) net ionic charge | -2 alternate names | trioxocarbonate | trioxidocarbonate | carbonate | carbonate(2-)
Ionic radius
thermochemical radius | 178 pm
Units
Other properties
ion class | anions | ionic conjugate bases | oxoanions | polyatomic ions common sources of ion | strontium carbonate (1 eq) | sodium percarbonate (2 eq) | sodium carbonate decahydrate (1 eq) | soda ash (1 eq) | samarium(III) carbonate hydrate (3 eq) | rubidium carbonate (1 eq) | pearl ash (1 eq)
Thermodynamic properties
molar free energy of formation Δ_fG° | aqueous | -527.8 kJ/mol (kilojoules per mole) molar heat of formation Δ_fH° | aqueous | -677.1 kJ/mol (kilojoules per mole) molar entropy S° | aqueous | -56.9 J/(mol K) (joules per mole kelvin)