Ligands and complexes

Question 1

a ligand is

Answer 1

a species that use a lone pair of electrons to form a dative bond with a metal ion

Question 2

a complex is

Answer 2

a species containing a metal ion joined to ligands

Question 3

a complex ion is

Answer 3

a complex with an overall positive or negative charge

Question 4

the coordination number is

Answer 4

the number of dative bonds in the complex

Question 5

transition metal ions have………………..radii

Answer 5

relatively smaller ions, meaning they can attract electron-rich species more strongly
these electron sich species, such as H2O are called ligands

Question 6

water molecules are attracted so strongly that

Answer 6

they form a specific number of bonds, usually six, giving a hexagonal shape

Question 7

the two ways of showing the structure of complex ions formed with H2O molecules are:

Answer 7

1) -showing dative bands with arrows from lone pair of electron on oxygen to metal ion
- inside square brackets
- original charge of metal ion, e.g. Fe2+, displayed outside of square brackets
2) - using solid wedges and hatched wedges and lines to show the 3D structure, also in square brackets and with the original charge shown

Question 8

in equations we show complex ions through:

Answer 8

e.g.
[Fe(H2O)]2+

all inside square brackets, except for the charge on the outside

Question 9

4 common species that act as ligands are:

show name, formula, charge and name in complex

Answer 9

water: H2O : 0 : aqua
hydroxide: -OH : -1 : hydroxo
ammonia: NH3 : 0 : ammine
chloride: Cl- : -1 : chloro

Question 10

ligands with a negative charge end with an…………..

Answer 10

-o in the complex name

Question 11

the order to naming complex ions is:

Answer 11

naming order:

• number of ligands
• name of ligand (if two or more ligand present, place in alphabetical order)
• name of metal ion
• oxidation number of the metal ion

Question 12

name the following:
[Fe(H2O)6]2+
[FeCl4]-
[Cu(NH3)4(H2O)2]2+

Answer 12

[Fe(H2O)6]2+
hexaaquairon(II)
[FeCl4]-
tetrachloroferrate(III) *
[Cu(NH3)4(H2O)2]2+
tetramminediaquacopper(II)

*the overall cgarge is 1- because the ion is formed from a Fe3+ ion and four Cl- ions, so the ‘-ate’ is added to the metal to show tthat it is part of the negatively charged complex ion
as it is negatively charged, the Latin name ‘ferrum’ (for ion) is used