F325 - Transition Elements

Question 0

Which two elements do not fill their subshells according to the conventional structure? Why?

Answer 0

Cr - 4s1 3d5 - to have one electron in each of the d subshells

Cu - 4s1 3d10 - to have full d subshells

Question 1

What is a transition element?

Answer 1

An element that forms at least one ion with a partly filled d subshell.

Question 2

What are the main properties of transition elements and their compounds?

Answer 2

• variable oxidation states
• used as catalysts
• form coloured compounds
• form precipitates on addition of sodium hydroxide

Question 3

What is the colour change in the formation of the copper(II) hydroxide precipitate?

Answer 3

Blue solution to Pale blue precipitate

Question 4

What is the colour change in the formation of the iron(II) hydroxide precipitate?

Answer 4

Green solution to Green precipitate

Question 5

What is the colour change in the formation of the iron(III) hydroxide precipitate?

Answer 5

Yellow solution to Rust precipitate

Question 6

What is the colour change in the formation of the cobalt(II) hydroxide precipitate?

Answer 6

Pink solution to blue-green precipitate

Question 7

What is a ligand?

Answer 7

A species that can use one or more lone-pairs to form dative covalent bonds to a transition metal ion, forming a complex.

Question 8

What is a complex ion?

Answer 8

A transition metal ion bonded to one or more electron-donating species (ligands) by dative covalent bonds from the ligands to the metal.

Question 9

What is the coordination number?

Answer 9

The number of dative bonds formed between the ligands and a central transition metal ion in a complex.

Question 10

What shape and bond angles would a complex with a coordination number of six have?

Answer 10

Octahedral

90

Question 11

What shape and bond angles would a complex with a coordination number of four have?

Answer 11

Tetrahedral, 109.5

Or

Square planar, 90

Question 12

What does the term bidentate ligand mean?

Answer 12

A ligand that has two lone-pairs of electrons which can form two separate dative covalent bonds to a transition metal ion.

Question 13

What are the two types of stereoisomerism shown by complexes?

Answer 13

• cis-trans isomerism

- optical isomerism

Question 14

In an octahedral complex what are the bond angles between the two ligands to show the cis- isomer and to show the trans- isomer?

Answer 14

Cis - 90

Trans - 180

Question 15

Besides octahedral what other shape of complex can show cis-trans isomerism?

Answer 15

Square planar

Question 16

How is cis-platin used as an anti-cancer drug?

Answer 16

• cis-platin binds to the DNA in a cell
• it binds the two strands of DNA together so that the cell is unable to copy it’s DNA
• this makes the cell incapable of dividing and causes it to die
• it does this more effectively in fast-growing cells than trans-isomer

Question 17

What is meant by the term optical isomerism?

Answer 17

Molecules that are non-superimposable mirror images of each other. The two isomers (enantiomers) rotate the plane polarised light in opposite directions.

Question 18

What shape of complex shows optical isomerism?

Answer 18

Octahedral

Question 19

What is the colour change associated with the ligand substitution of aqueous copper(II) sulphate on the addition of concentrated hydrochloric acid?

Answer 19

Light blue solution to yellow solution

Question 20

What is the colour change associated with the ligand substitution of aqueous copper(II) sulphate on the addition of concentrated ammonia?

Answer 20

Blue solution to a (light blue precipitate followed by a) dark blue solution

Question 21

What is the colour change associated with the ligand substitution of aqueous cobalt(II) chloride on the addition of concentrated chloride ions?

Answer 21

Pink solution to a blue solution