The formation and shapes of complex ions Flashcards
What is a complex ion?
An ion formed when one or more molecules or negatively charged ions bond to a central metal ion.
What are ligands?
Molecules or ions that donate a pair of electrons to a central metal ion to form a coordinate bond or a dative covalent bond.
How is a dative covalent bond or coordinate bond formed?
When one of the bonded atoms provides both of the electrons for the shared pair.
What does the coordination number indicate?
The number of coordinate bonds attached to the central metal ion.
Label this complex ion: [Cr(H2O)6]^3+?
- The square brackets are used to group all of the parts of the complex ions together = [].
- The ligand is inside the round brackets = H2O. The number of ligands is shown outside the round brackets = 6.
- The overall charge of the complex is shown outside the square brackets = 3+/
What are the 2 main charges on a ligand? Example?
- Neutral: H20.
- Negative: OH-.
What is a monodentate ligand?
A ligand that is able to donate one pair of electrons to a central metal ion, forming one coordinate bond.
What is are 2 examples of a negative and neutral monodentate ligand?
- Negative: chloride/hydroxide.
- Neutral: water/ammonia.
What is a bendentate ligand?
Ligands that can donate two pairs of electrons to a central metal ion, forming two coordinate bonds.
What are the 2 most common bidentate ligands?
- 1,2-diminoethane (en).
- Ethanedioate (oxalate) ion.
How does 1,2-diminoethane (en) act as a bidentate ligand?
Each nitrogen atom donates a pair of electrons to the central metal ion forming a coordinate bond.
How does ethanedioate (oxalate) ion act as a bidentate ligand?
Each negatively-charged oxygen atom donates a lone pair of electrons to the central metal ion.
What is an example of a complex ion containing a bidentate ligand? What does this complex contain (oxidation number, coordination number)?
[Co(NH2CH2CH2NH2)3]^3+:
- Oxidation number = 3+.
- Coordination number = 6 because there are 3 1,2-diminoethane (en) ligands and each ligand froms 2 coordinate bonds.
What does the shape of complex molecule ions depend on?
Coordination number.
What are the most common coordination number? (2)?
4 and 6.
What shape does a complex ion have that has 6 coordination numbers? Bond angle?
Octahedral shape, a 90 degree bond angle.
What is an example of a complex ion with 6 coordinate bonds and so an octahedral shape?
[Mn(H2O)6]^2+.
What 2 possible shapes does a complex ion have that has 4 coordination numbers? Most common? Bond angles?
- Tetrahedral - the most common, a 109.5 degree bond angle.
- Square planar, a 90 degree bond angle.
What are the 2 most common examples of a complex ion with a tetrahedral shape (4 coordination bonds)?
- [CoCl4]^2-.
- [CuCl4]^2-.
When does a square planar shape occur in a complex ion with 4 coordinate bonds?
Transition metals with 8 d-electrons in the highest energy d sub-shell.
What 3 transition metals have a square planar shape? (3)?
- Platinum (II).
- Palladium (II).
- Gold (III).
What is the most common example of a complex ion with a square planar shape (4 coordination bonds)?
[Pt(NH3)4]^2+.
