5.3.1 - Transition Elements Flashcards
What is a transition element?
A d-block element that has at least one stable ion with an incomplete d subshell.
What are the exceptions when doing electron configuration?
Chromium and copper.
What is the electron configuration of chromium?
[Ar]3d5 4s1
What is the electron configuration of copper?
[Ar] 3d10 4s1
Why is the electron configuration different for copper and chromium?
The 4s subshell and 3d subshell are very close in energy. Therefore there is only one electron in the 4s subshell. This reduces electron repulsions and gives chromium extra stability from a half filled 3d subshell and copper extra stability from a full 3d subshell.
Where are electrons lost from when forming ions?
Lost from the 4s first, then the 3d.
Why are ions formed this way?
The 3d and 4s subshells are close in energy and once they are occupied, repulsion between the electrons causes the 4s subshell to have a higher energy than the 3d.
Why are scandium and zinc not transition elements?
They form ions without an incomplete subshell.
What are the properties of transition metals?
They exist in more than one oxidation state. They form coloured solutions when dissolved in water, they frequently catalyse chemical reactions.
Fe2+
Green
Fe3+
Brown
Mn2+
Pale pink
Mn7+
Purple
Cu2+
Blue
Cr2+
Blue
Cr3+
Green
Cr6+
Orange
Ni2+
Green
Examples of when transition metals catalyse reactions?
Iron in the Haber process, nickel in hydrogenation of C=C bonds, vanadium (V) oxide in the contact process.
Complex ion?
A central transition metal ion bonded to one or more ligands by coordinate bonds.
Ligand?
An ion or molecule with a lone pair of electrons that can be donated to a transition metal to form a coordinate bond.
Coordinate number?
The total number of coordinate bonds between a central metal ion and its ligand.
Monodentate ligand?
A ligand that donates one pair of electrons to the central metal ion.
Water as a monodentate ligand?
:OH2 no charge
Ammonia as a monodentate ligand?
:NH3 no charge
Thiocynate as a monodentate ligand?
:SCN- -1
Cyanide as a monodentate ligand?
:CN- -1
Chloride as a monodentate ligand?
:Cl- -1
Hydroxide as a monodentate ligand?
:OH- -1
What is a bidentate ligand?
One that donates two pairs of electrons to the central transition metal ion forming 2 coordinate bonds.
What is the name and bond angle of a complex ions with 6 coordinate bonds?
Octahedral 90 degrees.
What is the name and bond angle of a complex ion with 4 coordinate bonds?
Tetrahedral 109.5, square planar 90 degrees.