Transition Metals Flashcards
Why do the electron arrangements of the transition metals explain their overall similarity?
In general there are two outer 4s electrons and as you go across the period, electrons are added to the inner 3d sub-level
Name some properties of the elements from titanium to copper
- good conductors of heat and electricity
- hard
- strong
- shiny
- have high melting and boiling points
- fairly low chemical reactivity
How does Copper differ from the general electronic configuration of the transition metals?
The d-sub-Level is full (3d10) in Copper and there is only one electron in the 4s outer level
How does Chromium differ from the general electronic configurations of transition metals?
It has a half full 3d-sub-level (3d5) and only one electron in the 4s outer level. It is believed that a half full d-level makes the atoms more stable in the same way as a full outer main level makes the noble gas atoms stable
Give the electronic configuration of Copper and a Copper 2+ ion.
(Atomic number is 29)
Copper = 1s2 2s2 2p6 3s2 3p6 3d10 4s1
Copper 2+ ion = 1s2 2s2 2p6 3s2 3p6 3d9
Give the electronic configuration of chromium and the chromium 3+ ion
(Atomic number is 24)
Chromium = 1s2 2s2 2p6 3s2 3p6 3d5 4s1
Chromium 3+ ion = 1s2 2s2 2p6 3s2 3p6 3d3
Where are electrons lost from when ions are formed in transition metals?
Electrons are first lost from the 4s sub-level
What is the formal definition of a transition metal?
One that forms at least one stable ion with a part full d-shell of electrons
What are the four main fractures of transition metals that are common to all the elements?
- variable oxidation states: they have more than one oxidation state in their compounds which means they can take part in many redox reactions
- colour
- catalysis: catalysts affect the rate of reaction without being used up or chemically changed themselves
- complex formation: transition elements form complex ions
What bonds do all transition metal ions form?
Coordinate/ dative bonds as they accept electron pairs from other ions or molecules
What is a ligand?
An ion or molecule with a lone pair of electrons that forms a coordinate bond with a transition metal
What is the coordination number?
The number of coordinate bonds to ligands that surround the d-block metal ion
What shape do ions with the coordination number 6 have?
Octahedral
What shapes are ions with coordination number 4?
Mostly tetrahedral but some complexes are square planar
What shape ions do Ag+ complexes form? And what are the bond angles?
Linear and 180 degrees
What shape do Pt2+ and Ni2+ complexes form and what are the bond angles?
Square planar and 90 degrees
What are the bond angles of tetrahedral complexes?
109.5 degrees
What happens when you dissolve the salt of a transition metal in water?
The positively charged metal ion becomes surrounded by water molecules acting as ligands. Such species are called aqua ions
What are multidentate ligands?
Molecules or ions with more than one atom with a lone pair of electrons which can bond to a transition metal ion
Why is Ethane-1,2-diamine a bidentate ligand?
Each nitrogen has a lone pair which can form a coordinate bond to the metal ion. The name of this ion is often abbreviated to ‘en’. It is a neutral ligand
What is the charge on an EDTA ion?
4-
What are chelates?
Complex ions with polydentate ligands
What can chelates be used for?
To remove d-block metal ions from solution
What happens when a polydentate ligand is added to a solution of a transition metal ion salt?
The chelates will replace all 6 water ligands in the aqua ion
Why are chelate complexes favoured over complexes with monodentate ligands?
Because the increase in the number of particles causes a significant increase in entropy which drives the reaction to the right- the chelate effect
What are isomers?
Isomers are compounds with the same molecular formula but with different arrangements of their atoms in space
Why can’t chloride ions form octahedral complexes?
Because they’re larger ligands than those such as ammonia and so fewer ligands can fit around the central metal ion
In which complexes does geometrical isomerism take place?
Octahedral and square planar complexes
In transition metal complexes, when does optical isomerism occur?
When there are two or more bidentate ligands in a complex
Why are optical isomers said to be chiral?
Because they have an effect on plane-polarised light. One isomer with rotate the plane polarised light in one direction and the other isomer in the opposite direction
What causes transition metals to be coloured?
The compounds absorbing energy that corresponds to light in the visible region of the spectrum
Explain how a solution appears purple in terms of light absorption
If a solution appears purple, it is because it absorbs all the light from a beam of white light shone at it except red and blue. The red and blue light passes through and the solution appears purple
Why are transition metal complexes coloured?
Transition metal compounds are coloured because they have part-filled d-orbitals. It is therefore possible for electrons to move from one d-orbital to another.
In an isolated transition metal atom, all the d-orbitals are of exactly the same energy but in a compound the presence of other atoms makes the d-orbitals have slightly different energies. Therefore, when electrons move between orbitals, they often absorb energy in the visible region of the spectrum. This colour is therefore missing from the spectrum and you see the combination of the colours that aren’t absorbed
Give the equation which relates energy difference, frequency and Planck’s constant
^E= hv
