Specify the number of unpaired electrons for each of the species shown below.
CuCl2- (linear)
Ni(NH36) 2+
NiCl4 2- (tetrahedral)
CoF6 3- (weak field)
Co(en)3 3+ (strong field) (en = "ethylene diamine")
Would it be:
1
2
2
3
3
??
To determine the number of unpaired electrons in each species, we need to consider the electronic configuration and the number of electrons in each species. Let's analyze each species step by step:
1. CuCl2- (linear):
Copper (Cu) has an atomic number of 29, so its electronic configuration is [Ar] 3d10 4s1. Since the coordination complex is linear, the 4s and three of the 3d electrons do not participate in bonding, leaving a single unpaired electron.
Answer: 1 unpaired electron.
2. Ni(NH₃)₆²⁺:
Nickel (Ni) has an atomic number of 28, so its electronic configuration is [Ar] 3d8 4s2. In the coordination complex, each ammonia (NH₃) ligand donates a pair of electrons to the central metal. Therefore, the d8 electrons pair up with the six pairs of electrons from the NH₃ ligands.
Answer: 0 unpaired electrons.
3. NiCl₄²⁻ (tetrahedral):
Again, nickel (Ni) has an atomic number of 28, so its electronic configuration is [Ar] 3d8 4s2. In this tetrahedral complex, all four chloride (Cl-) ligands donate a pair of electrons, pairing up with the eight d-shell electrons.
Answer: 0 unpaired electrons.
4. CoF₆³⁻ (weak field):
Cobalt (Co) has an atomic number of 27, so its electronic configuration is [Ar] 3d7 4s2. In this complex, the six fluoride (F-) ligands donate a pair of electrons each, pairing up with the seven d-shell electrons.
Answer: 0 unpaired electrons.
5. Co(en)₃³⁺ (strong field) (en = "ethylene diamine"):
Cobalt (Co) has an atomic number of 27, so its electronic configuration is [Ar] 3d7 4s2. In this complex, each en (ethylene diamine) ligand donates a pair of electrons, resulting in two unpaired electrons as they pair with three d-shell electrons.
Answer: 2 unpaired electrons.
To determine the number of unpaired electrons for each species shown, we need to consider the electron configuration and the ligand field splitting effect.
1. CuCl2- (linear):
Copper (Cu) has the electron configuration [Ar] 3d^10 4s^1. The chloride ion (Cl-) is a weak field ligand, which means it does not cause significant splitting of the d-orbitals. In the linear complex, the d-orbitals are not affected by the ligand field splitting. Since Cu has one unpaired electron in its d-orbitals, the answer is 1.
2. Ni(NH3)6 2+:
Nickel (Ni) has the electron configuration [Ar] 3d^8 4s^2. The ammonia ligand (NH3) is a weak field ligand, so it does not cause significant splitting of the d-orbitals. Since Ni has two unpaired electrons in its d-orbitals, the answer is 2.
3. NiCl4 2- (tetrahedral):
Nickel (Ni) has the electron configuration [Ar] 3d^8 4s^2. The chloride ion (Cl-) is a weak field ligand. In a tetrahedral complex, the d-orbitals split into two energy levels. The lower level has a triply degenerate set of orbitals (t2) and the higher level has a doubly degenerate set of orbitals (e). In this case, the energy difference between the two levels is relatively small compared to the pairing energy. Therefore, the electrons fill the lower energy level first, resulting in a low-spin configuration, where all the electrons are paired. So, there are no unpaired electrons, and the answer is 0.
4. CoF6 3- (weak field):
Cobalt (Co) has the electron configuration [Ar] 3d^7 4s^2. The fluoride ion (F-) is a strong field ligand, which causes significant splitting of the d-orbitals. In a weak field, the bottom energy level is the t2g level, which contains three orbitals, and the top energy level is the eg level, which contains two orbitals. Electrons fill the t2g level first before occupying the eg level. Since Co has one unpaired electron in the t2g level, the answer is 1.
5. Co(en)3 3+ (strong field) (en = "ethylene diamine"):
Cobalt (Co) has the electron configuration [Ar] 3d^7 4s^2. The ethylene diamine (en) ligand is a strong field ligand, so it causes significant splitting of the d-orbitals. In a strong field, the bottom energy level is the eg level, which contains two orbitals, and the top energy level is the t2g level, which contains three orbitals. Electrons fill the eg level first before occupying the t2g level. Since Co has three unpaired electrons in the eg level, the answer is 3.
So, the correct number of unpaired electrons for each species is:
CuCl2-: 1
Ni(NH3)6 2+: 2
NiCl4 2-: 0
CoF6 3-: 1
Co(en)3 3+: 3