Unit 1-5) Transition Metals And Oxidation Numbers Flashcards
What are transition metals
Transition metals are those which have an incomplete d sub shell in at least one of their ions
What are the general properties of transition metals
- they have atoms or ions with incomplete d sub shells
- they can form complexes
- have variable oxidation states
- show catalytic ability
Where are transition metals found and what are they known as
Transition metals are found between groups 2 and 3 on the periodic table and are known as the d block elements
Important uses of transition metals
- piping
- electrical wiring
- coinage
- construction and jewellery
The arrangement of the atoms in the periodic table can be explained in terms of the filling of the electron ______ _______
The arrangement of the atoms in the periodic table can be explained in terms of the filling of the electron energy levels.
Remember each energy level contains a number of sub shells
- first energy level - 1s
- second energy level - 2s ,2p
- third energy level - 3s, 3p , 3d
- fourth energy level - 4s , 4p , 4d , 4f
Remember the sub shells are filled in order of increasing energy : what is the order
1s, 2s, 2p, 3s, 3p, 4s, 3d 4p, 5s, 4d,
Why are scandium and zinc often considered not to be transition metals
- scandium only forms 3+ ions and zinc only forms 2+ ions. Neither of these result in an incomplete d sub shell , therefore they do not fit the definition of a transition metal
Look at the electron configurations of transition metals (in notes) - why do copper and chromium not follow the aufbau principle
- this is because there is a special stability associated with either half filled or completely filled d orbitals. This is why chromium is (Ar)3d^5 4s^1 rather than 3d^4 4s^2
Half filled or fully filled orbitals have _______ ________
Half filled or fully filled orbitals have special stability
When transition metal form ions ,how are the electrons lost
- when any transition metal atom forms an ion , the electrons that are lost first are those in the outer sub shell , the 4s electrons ( the ones that are lost first are the ones which require the least energy to loose them )
Oxidation state / oxidation number
The oxidation state is similar to the valency that an element has when it is part of a compound . Iron (ii) chloride would normally be stated as having iron with a valency of 2, but it is actually more accurate to say that the iron is in an oxidation state (II) or has oxidation number +2
Oxidation number rules
Rule 1
- the oxidation number of an ___________ element is __
The oxidation number of an uncombined element is 0
Rule 2
- for ions containing _______ atoms such as Na+ or O2- the oxidation number is the same as the ______ on its ion.
- for ions containing single atoms such as Na+ or O2- the oxidation number is the same as the charge on its ion
- in the examples given this would be +1 and -2
Rule 3
- in most of its compound oxygen has oxidation number _____
Except in hydrogen peroxide where it is ____
In most compounds oxygen abs oxidation number -2
Except in hydrogen peroxide where it is -1
Rule 4
- hydrogen has oxidation state ___ apart from in hydrides where it is ____
Hydrogen has oxidation state +1 apart from in hydrides where it is -1
