Chemistry Test - 11

Concept:​

• An atom consists of many orbitals that are distinguished from each other based on their shape, size, and orientation in space.

• There are four quantum numbers n, l, m, s which are used to identify an electron.

• The azimuthal quantum number determines the three-dimensional shape of the orbital quantum number and is responsible for the shapes of 5 d orbitals

Explanation:

• Orbitals having the same energy levels are called degenerate orbitals.
• Orbitals having the same principal quantum number ' n ' and azimuthal quantum number ' l ' are generally degenerate.
• The d-orbitals have ' l ' value = 2, so when they have the same value of ' n ', they will be degenerate.
• The shape is called baby-soother type shape whereas the others are clover-shaped.

​

Hence, the d orbitals that have a different shape but degenerate with the rest of the d orbitals are dz2. 

Additional Information

• The shapes are obtained through the wave functions of electron distribution which is different for different values of magnetic quantum number ' m '.

Concept:

Crystal field theory:

• A metal ion in a complex is surrounded by coordinating ligands anions or negative ends.
• An electric field is produced at the metal ion by the surrounding ligands.
• This electrostatic approach towards the interaction between metals and ligands is known as crystal field theory.
• CFT theory considers the ligands as point charges.
• There is no overlap between the ligand orbitals and metal ion orbitals.
• Ligands donate lone pair of electrons to the metal atoms and form coordinate complexes.

The geometry of the complex formed.

• Placement of the donor atoms at different stereochemical positions will perturb the metal ions to a different extent.
• This will result in the formation of different stereochemistries or structures.
• The stereochemistry also depends on the coordination number and the type of orbitals involved.

Explanation:

• Platinum (Pt) in the complex  [PtCl4]2- is in a +2 oxidation state. Hence the electronic configuration is [Xe]4f¹⁴5d8.
• Out of 8 5d electrons, 6 are paired and two are unpaired in the ground state.
• The CFSE of a square planar complex is:

• In presence of CFSE, the degeneracy of the d_x²-y² and d_z² breaks further.
• Thus, all the electrons gets paired leaving one of the d orbitals vacant.
• Hence, inner 5d, 6s and 6p orbitals are involved in hybridisation.
• The resulting hybridisation is dsp² and the geometry is square planar.

​

Hence, the shape of [PtCl4]2- is square planar.

Concept:

According to Werner’s theory,

• one of the five molecules of H₂O molecules will attach to the SO₄ molecules in the form of hydrogen bonding.
• It will act as both a primary and secondary molecules so the coordination number will be 4.

Explanation:

• Copper sulphate pentahydrate contains copper (II) in a geometry best described as distorted octahedral.
• The copper (II) is bound to four water molecules in a square-planar geometry and two oxygen atoms from two sulphate ions (one H₂O is H-Bonded here).

This salt dissolves in water to produce the pale-blue [Cu(H₂O)₆]²⁺ ion, in which two of the water molecules are less tightly held and have longer bond distances.

• In CuSO_4.5H₂O, four H₂O molecules are directly coordinated to the central metal ion (Cu⁺²) while one H₂O molecule is hydrogen bonded with SO₄^2-.

Explanation:

Δ₀ order will be compared by Spectro chemical series, not by energies of violet and yellow light

Δ₀ order is [Cr(H₂O)₆]Cl₃ < [Cr(NH₃)₆]Cl₃ 

Concept:

When ligands attach to a transition metal to form a coordination complex, electrons in the d orbital split into high energy and low energy orbitals.

The difference in energy of the two levels is denoted as ∆, and it is a characteristic property both of the metal and the ligands, the "o" subscript on the ∆ indicates that the complex has octahedral geometry.

• ‘A’ [Cr(H₂O)₆]Cl₃ Hexaaquachromium (III) chloride absorbs yellow light of less energy and emits the violet light of high energy with complementary colour because  H₂O a is weak field ligand.
• But when we consider a case ‘B’ [Cr(NH₃)₆]Cl₃ Hexaamminechromium (III) chloride, due to presence of strong field ligand NH₃, it absorbs high energy violet light and emits low energy complementary colour.

The energy difference, Δ_o, determines the color of the coordination complex. According to the spectrochemical series, the high spin ligands are considered “weak field”, and absorb longer wavelengths of light (weak Δ_o), while complexes with low spin ligands absorb light of greater frequency (high Δo). ∆₀ order will be compared by spectro chemical series not by energies of violet & yellow light so Δo order is

[Cr(H₂O)₆] Cl₃<[Cr(NH₃)₆ ] Cl₃

Explanation:

• The complex given here is [Cu (NH3)4]SO4.
• Hybridization is dsp², square planar with one unpaired electron (Paramagnetic)
• The coordination sphere is non-ionizable, when the complex breaks, it forms:

 [Cu (NH3)4]SO4 ⇔  [Cu (NH3)4]+2 + SO42-

• The bond between Cu and ammonia is not broken due to the presence of a strong Co-ordinate bond between them.

Additional Information ​Crystal field theory:

• A metal ion in a complex is surrounded by coordinating ligands anions or negative ends.
• An electric field is produced at the metal ion by the surrounding ligands.
• This electrostatic approach towards the interaction between metals and ligands is known as crystal field theory.
• CFT theory considers the ligands as point charges.
• There is no overlap between the ligand orbitals and metal ion orbitals.
• Ligands donate lone pair of electrons to the metal atoms and form coordinate complexes.
• The bond formed by the ligands and the metal ion forms a coordination sphere.
• The coordination sphere is non-ionizable in solution because of the co-ordinate bond between them.
• The oxidation number or primary valency of the metal ion is satisfied by the side ions which form the ionizable sphere.

Concept:

The structure of Co₂(CO)₈ (a polynuclear metal carbonyl) can be written as:

Concept:

Co-ordination complexes and CFT:

• A metal ion in a complex is surrounded by coordinating ligands anions or negative ends.
• An electric field is produced at the metal ion by the surrounding ligands.
• This electrostatic approach towards the interaction between metals and ligands is known as crystal field theory.
• CFT theory considers the ligands as point charges.
• There is no overlap between the ligand orbitals and metal ion orbitals.
• Ligands donate lone pair of electrons to the metal atoms and form coordinate complexes.

Explanation:

• The metal ion has two valencies:
  • The oxidation state or the primary valency.
  • The coordination number or the secondary valency.
• The secondary valencies are satisfied by coordinating with primary ligands.
• The bond formed by the ligands and the metal ion forms a coordination sphere.
• The coordination sphere is non-ionizable in solution because of the co-ordinate bond between them.
• The oxidation number or primary valency of the metal ion is satisfied by the side ions which form the ionizable sphere.
• For example:

• In the complex [Ni(NH3)4]Cl2, Nickel is the central metal atom. Its coordination number is four.
• The Coordination sites are occupied by four ammonia ligands, which are neutral in charge.
• The overall charge on Ni ion is +2, which is satisfied by the two chloride ions.
• In solution, the ammine molecules are non-ionizable but the chloride ions are hence, the number of ions furnished will be two.
• The dissociation takes place as:

[Ni(NH3)4]Cl2 → [Ni(NH3)4]²⁺ + 2Cl^-

On Ionisation, we get 2 Cl^- ions & 1 [Ni(NH3)4]2+ ion

Hence, the number of ions furnished per molecule of the complex [Ni(NH3)4]Cl2 is Three.

Concept:

Mn₂(CO)₁₀ is an organometallic compound due to the presence of Mn–C bond. The metal-carbon bond in organometallic compounds possess both σ and –π character. The M–C, σ bond is formed by the donation of lone pair of electrons from the carbonyl carbon into a vacant orbital of the metal. The M–C, and π–bonds are formed by the donation of pair of electrons from a filled d-orbital of metal into vacant antibonding π* orbital of CO. The M–L bonding creates a synergic effect which strengthens the bond between CO and the metal.

The structure of Mn₂(CO)₁₀ is shown below.

Concept-

​Crystal field theory:

• A metal ion in a complex is surrounded by coordinating ligands anions or negative ends.
• An electric field is produced at the metal ion by the surrounding ligands.
• This electrostatic approach towards the interaction between metals and ligands is known as crystal field theory.
• CFT theory considers the ligands as point charges.
• There is no overlap between the ligand orbitals and metal ion orbitals.
• Ligands donate lone pair of electrons to the metal atoms and form coordinate complexes.

Geometry of the complex formed.

• Placement of the donor atoms at different stereochemical positions will perturb the metal ions to a different extent.
• This will result in the formation of different stereochemistries or structure.
• The stereochemistry depends on the co-ordination number.

Explanation:

• The complex given here is [Co(NH3)6]3+  
• The complex has sp³d² hybridization which means 4d, 4s, and 4p orbitals of Cobalt are involved and the cation has +3 charge.
• The ligand ammonia is a strong field ligand and forms low spin complexes.
• The cation undergoes hybridisation in the following way-

• Six ligands are attached and it corresponds to C.N number six which gives octahedral geometry.

Additional Information

• Strong field ligands produce a greater amount of perturbation
• Weak field ligands produce a lower amount of perturbation.
• Ammonia is was strong field ligand and it produces spin pairing in the following way

• Experimental data also suggest that it has d²sp³ hybridisation.

Concept:

IUPAC stands for International Union of Pure and Applied Chemistry. In this, the naming of the compound is followed by a certain rule to avoid confusion all over the world.

As per IUPAC rules, additive nomenclature was founded in order to describe the structures of coordination entities or complexes, but this method is readily extended to other molecular entities as well. 

Mononuclear complexes are considered to consist of a central atom, often a metal ion, which is bonded to surrounding small molecules or ions, which are referred to as ligands

Explanation:

The oxidation state of Co in [Co(NH3) 5 Cl]Cl 2 is x : x + 5 × 0 - 1 = + 2 ⇒ x = +3. 

From the above explanation we know that in mononuclear complexes we have a central atom which is metal in our case it is Cobalt which is surrounded by ammonia and Clmolecules then its IUPAC name will be Pentaamminenitritocobalt (III) ion