Final answer:
To assign oxidation numbers, consider guidelines: in neutral compounds, sum is zero, Group 1 elements are +1, Group 2 elements are +2, oxygen is usually -2 except in peroxides where it is -1, and hydrogen is usually +1 except when bonded to a metal. The underlined atom in each compound has the following oxidation numbers: a) UO2²-: U is +4. b) As2O3: As is +3. c) NaBiO3: Bi is +5. d) Na2S2O3: S is +2. e) Hg2Cl2: Hg is +2. f) Ca(NO3)2: Ca is +2. g) CO3²-: C is +4. h) Cr2O7²-: Cr is +6.
Step-by-step explanation:
Oxidation numbers, also known as oxidation states, represent the charge an atom would have if all its bonds were 100% ionic. To assign oxidation numbers, consider the following guidelines:
- In a neutral compound, the sum of the oxidation numbers is zero.
- Group 1 elements (such as Na) have an oxidation number of +1, and Group 2 elements (such as Ca) have an oxidation number of +2.
- Oxygen usually has an oxidation number of -2, except in peroxides (such as Li2O2) where it has an oxidation number of -1.
- Hydrogen usually has an oxidation number of +1, except when it is bonded to a metal, where it has an oxidation number of -1.
- In an ion, the sum of the oxidation numbers is equal to the charge of the ion.
Using these guidelines, here are the oxidation numbers for the underlined atom in each compound:
a) UO22- (uranium dioxide): Uranium (U) has an oxidation number of +4.
b) As2O3 (arsenic trioxide): Arsenic (As) has an oxidation number of +3.
c) NaBiO3 (sodium bismuthate): Bismuth (Bi) has an oxidation number of +5.
d) Na2S2O3 (sodium thiosulfate): Sulfur (S) has an oxidation number of +2.
e) Hg2Cl2 (mercury(I) chloride): Mercury (Hg) has an oxidation number of +2.
f) Ca(NO3)2 (calcium nitrate): Calcium (Ca) has an oxidation number of +2.
g) CO32- (carbonate ion): Carbon (C) has an oxidation number of +4.
h) Cr2O72- (chromate ion): Chromium (Cr) has an oxidation number of +6.