Unit 5- Topic 17
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What are transition metals
Transition metals are d-block elements that form one or more stable ions with incompletely filled d-orbitals
Characteristics of transition metals
-hard solids -high melting and boiling points -can act as catalysts -form coloured ions and compounds -form ions with different oxidation numbers -form ions with incompletely filled d-orbitals -aqueous solutions of transition metal ions are usually coloured
In transition metal ions, what is the order in which the electrons fill in spdf notation
1s2s2p3s3p4s3d
Order in which electrons are lost in transition metals
4s3d3p3s2p2s1s
Why are electrons lost first in the 4s orbital rather than 3d
Because the 4s electrons have higher energy than the electrons in the 3d orbital.
What elements are the exception to the rule of electronic configuration
Chromium since it has 5 electrons in its 3d orbital but only 1 in its 4s orbital Copper since it has 10 electrons in its 3d orbital but only 1 in its 4s orbital
How are oxidation numbers created
Because each element can lose a variable number of electrons to form ions with different oxidation numbers.
What is special about transition metal ions with high oxidation numbers
That they usually contain an electronegative element
What affects the frequency in which we see high oxidation numbers in metal ions
Increasing the nuclear charge means that the electrons are attracted more strongly and are less likely to be involved in bonding. So higher oxidation numbers are lesss common
Why do transition metals have variable oxidation states
Because the 4s and 3d orbitals are very close in energy levels. This not only makes it possible for electrons to be lost from both orbitals relatively easily, but also means the remaining electrons form a stable configuration.
What is a ligand
A species that uses a lone pair of electrons to form dative bond with a metal ion
Why can transition metals form complex ions
Because they have a relatively small ionic radii that enables them to attract electron-rich species more strongly
What should the diagram of a complex ion show
-Bonds are shown with lines, indicating that they are dative (coordinate) bonds - one of the lone pairs of electrons on one atom of each molecule is used to form the bond. Both electrons come from the ligand. -whole structure is shown inside square brackets,and the original charge of the central metal ion is shown outside the brackets -the ligand molecules are arranged in a regular pattern around the Fe- due to the electron pair repulsion theory -solid wedges represent bonds coming out of the place of the paper -stripped wedges represent bonds going behind the plane of the paper
What is the coordinaton number
The number of dative (coordinate) bonds in the complex
What is a complex ions
A species containing a metal ion joined to ligands with an overall positive or negative charge
State the name and charge of this ligand -> water
Name in complex- aqua Charge- 0
State the name and charge of this ligand -> hydroxide
Name in complex- hydroxo Charge- -1
State the name and charge of this ligand -> ammonia
Name in complex- ammine Charge- 0
State the name and charge of this ligand -> chloride
Name in complex- chloro Charge- -1
Order followed in the naming of complex ions
-number of ligands (eg. Hexa) -name of ligand (s), if many order in alphabetical order (eg. Aqua) -name of metal ion (eg. Iron or ferrate if overall negative charge of complex ion) -oxidation number of the metal ion
what is a monodentate ligand
ligands which form one coordinate bond with the central metal ion. Eg: H2O
what is a bidentate ligand
ligands which form two coordinate bonds with the central metal ion. Eg: NH2CH2CH2NH2
what is a hexadentate ligand
ligands which form six coordinate bonds with the central metal ion. Eg: EDTA
what is a polydentate or multidentate ligand
general term for a ligand which forms more than one coordinate bond with the central metal ion