13.1 Transition metals (HL)

Question 1

Valency, charge and oxidation state of Copper in CuSO4

Answer 1

Valency= 2
Charge= 2+
Oxidation= +2

Question 2

Transition element

Answer 2

Element that forms atleast one stable ion with a partially filled d subshell

Question 3

Why is Scandium considered a transition element and why is this controversial?

Answer 3

Its configuration is [Ar] 3d1 4s2. This means that Sc2+ has an incomplete d subshell and hence is a transition element. However, it largely reacts as Sc3+ which means it doesn’t have a partially filled d subshell and that’s why its still debated.

Question 4

Is Zinc a transition metal and why or why not?

Answer 4

It is NOT a transition metal as both atom and ion (Zn2+) have a complete 3d sub shell

Question 5

Is Copper a transition metal?

Answer 5

Yes. Even though Cu and Cu+ have complete d subshells, Cu 2+ has an incomplete d sub shell

Question 6

What does the presence of unpaired electrons result in?

Answer 6

• Variable oxidation states
• Colored compounds
• Possible catalytic activity
• Formation of complex ions in solution
• Possible magnetic properties

Question 7

Calculate oxidation state of Mn in KMnO4

Answer 7

K= +1
O= -2 so O4= -8
–> 1+x-8=0 so x= +7

Question 8

What is the variable oxidation state that most transition elements have and why?

Answer 8

+2 except Scandium because they lose the 2 4s electrons first

Question 9

Why does variable oxidation state occur?

Answer 9

Because of the closeness of energy between 3d and 4s subshells. There is little change in atomic radii and less effective nuclear charge as electrons are added to 3d sublevel resulting in lower range of ionization energies. This allows them to lose electrons easily

Question 10

What are the variable oxidation states for Magnesium and why?

Answer 10

+2 only as it is in Group 2 so there is a large increase between 2nd and 3rd ionization energy. Therefore Mg cannot have +3

Question 11

What are the variable oxidation states for Titanium and why?

Answer 11

Large increase between 4th and 5th ionization energy so only +2, +3 and +4 (as +5 would require too much energy to remove)

Question 12

Why do transition metals have higher charge density and what does it do?

Answer 12

They are smaller than other elements. In solution, this high charge density attracts water molecules to form coordinate bonds with positive ions

Question 13

Complex ion

Answer 13

Formed when ligands bond to a central metal ion

Question 14

Ligand

Answer 14

Species with lone pair of electrons that act as a Lewis Base (they donate lone pair)

Question 15

Central metal ion

Answer 15

Acts as Lewis Acid as it accepts lone pair and forms coordinate covalent bond

Question 16

Coordination number

Answer 16

No. of coordinate covalent bonds between ligand and metal ion

Question 17

What types of ligands are there?

Answer 17

Neutral ligands (H2O, NH3) or charged ions (Cl-, CN-)

Question 18

What is a ligand that forms one coordinate covalent bond (only one pair of electrons involved)?

Answer 18

Monodentate ligand like H2O

Question 19

Besides monodentate ligands, what others exist?

Answer 19

Bidentate, polydentate and hexdentate

Question 20

What are the shape of most complexes?

Answer 20

Octahedral

Question 21

4 types of shapes for complexes and the number of bonds in each

Answer 21

Linear (2)
Square planar (4)
Tetrahedral (4)
Octahedral (6)

Question 22

What is oxidation state of Fe in [Fe(H2O)6]2+?

Answer 22

H2O is neutral so Fe must be +2

Question 23

What is oxidation state of Ni in [Ni(CN)4]2-?

Answer 23

CN has charge of 1- so x+(-1*4)= 2- hence Ni =+2

Question 24

What is a coordination compound?

Answer 24

Complex ion + counter ion

Question 25

Counter ion

Answer 25

Balances out charge of complex ion

Question 26

How can you neutralize [Fe(H2O)6]3+ with Cl?

Answer 26

Add 3 Cl- ions so it will become coordination compound –> [Fe(H2O)6]Cl3

Question 27

Why can’t CH4 be a ligand?

Answer 27

Because it has no lone pair of electrons

Question 28

What is dimagnetism?

Answer 28

When a substance only has paired electrons as opposite spin cancels out magnetic effect. Weak repulsion means non-magnetic eg. Zinc

Question 29

What is paramagnetism?

Answer 29

When a substance has atleast one half-filled orbital. Opposite spin shows attraction and hence magnetic effect.

Question 30

Is paramagnetic effect permanent?

Answer 30

No. Magnetic properties are not retained when external field is removed

Question 31

Which shows more attraction and why? MnO2 or Cu(NO3)2

Answer 31

• MnO2 will be more magnetic as:
• Mn will have charge of 4+ so config is [Ar] 3d3
• Cu will have charge of 2+ so config is [Ar] 3d9
• Mn has 3 unpaired orbitals while copper only has 1
• More unpaired orbitals= more attraction

Question 32

What do catalysts do?

Answer 32

They allow reactions to occur at lower temperature and pressure

Question 33

Heterogenous catalysts

Answer 33

When catalyst is in a different state than reactants

Question 34

Example of heterogenous catalyst

Answer 34

Haber process: Iron is solid but nitrogen and hydrogen are gaseous. Iron provides surface for absorption of gases and allows them to orient themselves to react

Question 35

Homogenous catalysts

Answer 35

Same physical state as reactants

Question 36

Why are homogenous catalysts effective in redox reactions?

Answer 36

Because of variable oxidation states

Question 37

Examples of homogenous catalysts

Answer 37

• Enzymes: Iron and Cobalt
• O2 in transport: Iron is central to heme group
• Vitamins: Co(III) ions are in B12