Chem Ch 8a quiz

Question 1

What are oxidation numbers

Answer 1

Possible charges an atom of an element can have (if all its bonds are ionic)

Question 2

Why do we have oxidation numbers

Answer 2

Keep track of electrons in bonding of 2 atoms
Represent number of electrons that an atom in a compound must gain or lose to return to its neutral state (charge = 0)

Question 3

Determining the oxidation number rules

Answer 3

1) (free-element rule): Pure elements + Atoms in natural form = 0
2) (ion rule): Monatomic ion is = ion’s charge
3) (zero-sum rule): Sum of all atom’s #s must be 0
4) Alkali metals +1, Alkaline earth +2, Hydrogen +1 (except when bonded to atoms -1)
Oxygen -2 (except when bonded to fluorine +1; -1 in peroxide ion)
Halogens -1 when bonded to metals, w nonmetals the element w higher electronegativity takes negative #
Fluorine ALWAYS -1 (Also Cl, Br, I)
5) Oxidation #s of all atoms in a polyatomic ion = its charge
(Also used 4 poly ionic compounds)

Question 4

Finding oxidation numbers

Answer 4

If 1 rule contradicts another rule, rule listed first is followed
For binary ionic compounds, crisscross method can be used

Question 5

Polyatomic ions are covalently bonded groups of atoms that carry a ____________

Answer 5

Charge

Question 6

Some atoms can have more than one

Answer 6

Oxidation #
EX: Transition metals
Iron (Fe): +2, +3, +6
Nitrogen (N): -3, +5

Question 7

Polyatomic ions are what kind of groups that carry what?

Answer 7

Covalently bonded groups of atoms that carry a charge