Oxidation numbers

Question 1

What are the oxidation number rules?

Answer 1

A set of rules to work is a redox is taking place and if so, which element is reduced and oxidised

Question 2

What is the most important oxidation rule?

Answer 2

Oxidation refers to an individual atom and are mostly always the same element and they are written with the +/- sign before the number

Question 3

What is oxidation number significance in covalent compounds?

Answer 3

It has no significance in covalent compounds (any compound with covalent bonding)

Question 4

What is the first oxidation number rule?

Answer 4

Atoms of uncombined always have an oxidation number of 0

Question 5

What is the second oxidation number rule?

Answer 5

Group 1 element atoms have an oxidation number of +1

Question 6

What is the third oxidation number rule?

Answer 6

Group 2 element atoms have an oxidation number of +2

Question 7

What is the fourth oxidation number rule?

Answer 7

Fluorine atoms have an oxidation number of -1

Question 8

What is the fifth oxidation number rule?

Answer 8

Oxygen atoms have an oxidation number of -2 except when in a peroxide (e.g, H2O2 - hydrogen peroxide) then it is -1

Question 9

What is the sixth oxidation number rule?

Answer 9

Hydrogen atoms have an oxidation number of +1 except when in a metal hydride (which is only metal & hydrogen , e.g, LiH) then it is -1

Question 10

What is the oxidation number rule about simple ions?

Answer 10

The sum of the oxidation numbers equals the charge on the ion, e.g, I- = -1

Question 11

What is the oxidation number rule about compound ions?

Answer 11

The oxidation numbers must all add up to the charge of the ion (in polyatomic ions), e.g, SO4 2- = -2

Question 12

What is the oxidation number rule about neutral compounds?

Answer 12

The sum of oxidation numbers is 0 (but must account for formula in compounds)

Question 13

What do roman numerals indicate?

Answer 13

The oxidation number of the element and they are always positive

Question 14

What do roman numerals after a metal indicate?

Answer 14

The oxidation number of the metal (but are only used when the metal can form more than one ion e.g, Fe(III) = Fe 3+

Question 15

What do roman numerals written after a compound ion indicate?

Answer 15

The oxidation number of the element in the ion which is not oxygen

Question 16

What is oxidation (in terms of oxidation number)?

Answer 16

Increase in oxidation number

Question 17

What is reduction (in terms of oxidation number)?

Answer 17

Decrease in oxidation number

Question 18

How do you work out which element has been oxidised and reduced using oxidation numbers?

Answer 18

First, assign oxidation numbers to everything in the equation (no balancing) and then identify the increase (oxidation) and decrease (reduction)

Question 19

How do you describe that an element has been oxidised?

Answer 19

(The element) has been oxidised because it’s oxidation number has increased from (X) to (Y)

Question 20

How do you describe if an element has been reduced?

Answer 20

(The element) has been reduced because it’s oxidation number has decreased from (X) to (Y)