Transition elements

Question 1

d-block element

Answer 1

An element with its highest energy e- in the d-subshell

Question 2

transition metal

Answer 2

A d-block element which forms at least one ion with an incomplete d-subshell

Question 3

What three types of reactions can transition elements undergo?

Answer 3

• ligand exchange
• precipitate
• redox

Question 4

chemical properties of transition elements (4)

Answer 4

• colourful
• good catalysts
• variable oxidation states
• complex ions with variety of ligands

Question 5

physical properties of transition elements (5)

Answer 5

• ductile
• malleable
• high melting/boiling pt
• hard/dense
• sonorous

Question 6

Why are transition elements good catalysts?

Answer 6

• variable oxidation states
• provide a surface which can absorb reactants (form complex ions)

Question 7

two examples of reactions which use transition metals as catalysts

Answer 7

• Ni (alkene –> alkane)
• V2O5 Contact process (SO2 + O2 –> 2SO3)

Question 8

ligand

Answer 8

A molecule or ion that can donate a pair of e- to the transition metal ion

Question 9

complex ion

Answer 9

A transition metal bonded to ligands by coordinate bonds

Question 10

coordinate number

Answer 10

Total number of coordinate bonds between a central metal ion and ligands

Question 11

shape of complex ion with 4 coordinate bonds

Answer 11

• square planar (90°)
• tetrahedral (109.5°)

Question 12

shape of complex ion with 6 coordinate bonds

Answer 12

octahedral (90°)

Question 13

bidentate ligands

Answer 13

ligands with two lone pairs of e-:
- en
- ethanedioate (2-)

Question 14

hexadentate ligands

Answer 14

ligands with six lone pairs of e-:
- edta (4-)

Question 15

neutral ligands (monodentate)

Answer 15

• H2O
• NH3

Question 16

charged ligands

Answer 16

• Cl-
• OH-
• CN-
• SCN-

Question 17

which two transition metals have unusual e- configurations?

Answer 17

Cr and Cu

Question 18

which d-block elements are not transition elements?

Answer 18

• Zn (Zn2+ has a full d-subshell)
• SC (Sc3+ doesn’t have a d-subshell)

Question 19

Cu2+ with NaOH(aq)

Answer 19

blue solution –> blue ppt
Cu(OH)2(s)

ppt insoluble in excess

Question 20

Fe2+ with NaOH(aq)

Answer 20

pale green solution –> dark green ppt (goes brown on standing in air)
Fe(OH)2(s)

ppt insoluble in excess

Question 21

Fe3+ with NaOH(aq)

Answer 21

pale yellow solution –> orange brown ppt

Fe(OH)3(aq)

ppt insoluble in excess

Question 22

Mn2+ with NaOH(aq)

Answer 22

pale pink solution –> light brown ppt (darkens on standing in air)

Mn(OH)2(s)

ppt insoluble in excess

Question 23

Cr3+ with NaOH(aq)

Answer 23

violet solution –> grey green ppt

Cr(OH)3(s)

ppt dissolves in excess to form a dark green solution

[Cr(OH)6]3-(aq)

Question 24

which ions react the same way with NH3(aq) as they do with NaOH(aq)

Answer 24

Fe2+
Fe3+
Mn2+

Question 25

Cu2+ with NH3(aq)

Answer 25

blue solution --> blue ppt Cu(OH)2(s) ppt dissolves in excess to form a dark blue solution (ligand exchange) [Cu(NH3)4(H2O)2]2+(aq)

Question 26

Cr3+ with NH3(aq)

Answer 26

violet solution --> grey green ppt Cr(OH)3(s) ppt dissolves in excess to form a purple solution (ligand exchange) [Cr(NH3)6]3+(aq)

Question 27

what transition metals can show optical isomerism?

Answer 27

ones with: - x3 bidentate ligands - CIS x2 monodentate + x2 bidentate

Question 28

which transition metal stereoisomers also show optical isomerism?

Answer 28

cis isomers ONLY (trans isomers DO NOT show optical isomerism)

Question 29

how does hemoglobin transport oxygen using ligand substitution?

Answer 29

- O forms dative covalent bond/coordinate bond with Fe2+ - oxygen bonds reversibly/can be replaced by CO2