15.1 Flashcards
define transition metal
an element that forms one or more stable ions with an incompletely filled d-orbitals
what are the characteristics of transition metals
are hard solids
high mp & bp
can act as a catalyst
form coloured ions & compounds
form ions with different oxidation states
form ions with incompletely filled d-orbitals
which 2 out of 10 elements in the d-block elements of period 4 are not transition metals and why
scandium & zinc
because they only form one ion and their compounds are not coloured
what is the electronic configuration of chromium
[Ar] 4s1 3d5
what is the electronic configuration of copper
[Ar] 4s1 3d10
how do transition metals lose electrons when they form ions
they lose electrons from their 4s subshell first then 3d
why are ions with high oxidation numbers less common
as electrons are lost they become more strongly attracted to the nuclei so they are less likely to be involved in bonding
why do Ti(4+) and Mn(7+) form the highest oxidation numbers
because all of their 4s and 3d electrons become involved in bonding
why do ligands form with transition metals
transition metals have small atomic radius in comparison to other atoms in the same period therefor they attract electron-rich species more strongly allowing them to form bonds
define ligand
a species that uses a lone pair of electrons to form a dative bond with a metal ion
what is a ligand complex
a species containing a metal ion joined to ligands
what is a complex ion
a ligand complex with an overall charge
what is the coordination number
the number of dative bonds in the complex
what are the 4 most common ligands and their names in a complex
water - aqua
hydroxide - hydroxo
ammonia - ammine
chloride - chloro
what is the name of the complex [Fe(H2O)6]^2+
hexaaquairon(II)
what is the name of the complex [FeCl4]-
tetrachloroferrate(III)
when is the latin name for the metal used when naming complexes
if the ion is negative
name the complex [Cu(NH3)4(H2O)2]^2+
tetraamminediaquacopper(II)
why do transition metals form coloured ions and compounds
because when ligands attach to the metal the d energy levels splits into 2 different energy levels and when light energy is absorbed an electron from the lower energy level is exited/promoted to the higher energy level and the complementary colour of the frequency absorbed is transmitted
what is the shape of a molecule that forms 6 ligands and its bond angle
octahedral
90
what is the shape of a molecule that forms 4 ligands and its bond angle
tetrahedral
109.5
what is the shape of a molecule that forms 2 ligands and its bond angle
linear
180
what is six-fold coordination
complexes in which there are 6 ligands forming coordinate bonds with the transition metal
what is the colour of hexaaquamanganese(II) [Mn(H2O)6]2+
very pale pink (usually seen as colourless)
what is the colour of tetraaquadihdryoxoiron(II) [Fe(H2O)4(OH)2)
pale green
what is the colour of hexahydroxoaluminate(III) [Al(OH)6]^3-
colourless
why do chlorine ligands often only form 4 coordinate bonds
because chlorine is a very large ion therefor there is not enough space around the central metal ion for 6
what is the square planar shape
contains a central or ion surrounded by four atoms or ligands in the same plane with bond angles of 90
why is cis-platin important
it is an effective treatment of cancer (especially testicular cancer)
describe the structure of cis-platin
central platinum(II) ion 2 ammonia ligands facing each other and 2 chloride ligands facing each other
summarise how cis-platin works
when cells divide the DNA must separate into 2 strands to be copied and cis-platin forms a bond between the 2 strands of DNA and prevents them from separating so the cancer cells can’t divide
why is cis-platin used and not trans-platin
trans-platin is much less effective and more toxic
what is a monodentate ligand
a ligand which forms one dative bond with a metal ion
what is a bidentate ligand
a ligand that forms 2 dative bonds with a metal ion
what is a multidentate ligand
a ligand that forms several dative bonds with a metal ion
what is the most common bidentate ligand
1,2, diaminoethane (ethylenediamine)
NH2CH2CH2NH2
how does the change from a monodentate ligand to a multidentate ligand effect the stability of the products
if 6 monodentate ligands are replaced by 1 multidentate ligand then there will be more species in the products therefor the system becomes more disordered which increases stability of the product
what ion plays an important role in heamoglobin
Fe2+
why is Fe2+ important in the haem group
oxygen uses one of it’s lone pairs to form a dative bond with an Fe2+ ion in the haem group
why is carbon monoxide toxic (in terms of dative bonds)
carbon monoxide has a lone pair of electrons so it can act as a ligand and when it comes into contact with haemoglobin it forms a stronger dative bond than oxygen so the oxygen is substituted and the dative bond between carbon monoxide and haemoglobin becomes extremely hard to overcome
