Oxidation state rules

Question 1

What is oxidation number of an element in its free (uncombined)?

For example, Al(s) or Zn(s). As well as the diatomic elements

H2, O2, N2, F2, Cl2, Br2, I2

and sulfur:

S8

Answer 1

Zero

Question 2

What is the oxidation number of a monatomic (one-atom) ion?

Answer 2

same as the charge on the ion, for example:

Na⁺ = +1

S^-2 = -2

Question 3

What is the sum of all oxidation numbers in a neutral compound? Also, what is the sum of all oxidation numbers in a polyatomic (many-atom) ion?

Answer 3

1. Zero
2. same as the charge on the molecule

Question 4

What is the oxidation number of an alkali metal (IA family) in a compound? Also, what is the oxidation number of an alkaline earth metal (IIA family) in a compound?

Answer 4

1. +1
2. +2

Question 5

The oxidation number of oxygen in a compound is usually _______. If, however, the oxygen is in a class of compounds called peroxides (for example, hydrogen peroxide), then the oxygen has an oxidation number of _______. If the oxygen is bonded to fluorine, the number is __________.

Answer 5

• -2
• -1
• +1

Question 6

The oxidation state of hydrogen in a compound is usually ________. If the hydrogen is part of a binary metal hydride (compound of hydrogen and some metal), then the oxidation state of hydrogen is _________.

Answer 6

• +1
• -1

Question 7

The oxidation number of fluorine is always _________. Chlorine, bromine, and iodine usually have an oxidation number of ________, unless they’re in combination with an __________ or _________.

Answer 7

• -1
• -1
• oxygen; fluorine

Question 8

• Lose of electrons
• Lose of H⁺
• Gain of O^-2

Answer 8

Oxidation

Question 9

• Gain of electrons
• Gain of H⁺
• Lose of O^-2

Answer 9

Reduction