Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth,
fifth and sixth periods with proper illustration.
Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth,
fifth and sixth periods with proper illustration.| Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth, |
| :— |
| fifth and sixth periods with proper illustration. |
b)
Explain periodic variation of electronegativity with atomic number for the first six rows
of the periodic table.
Explain periodic variation of electronegativity with atomic number for the first six rows
of the periodic table.| Explain periodic variation of electronegativity with atomic number for the first six rows |
| :— |
| of the periodic table. |
2 .
a)
What are the possible molecular structures of xenon hexafluoride? Explain with suitable
figures. Explain the geometrical isomers of Ma_(2)b_(2)cd\mathrm{Ma}_2 \mathrm{~b}_2 \mathrm{~cd} complex with suitable figures.
What are the possible molecular structures of xenon hexafluoride? Explain with suitable
figures. Explain the geometrical isomers of Ma_(2)b_(2)cd complex with suitable figures.| What are the possible molecular structures of xenon hexafluoride? Explain with suitable |
| :— |
| figures. Explain the geometrical isomers of $\mathrm{Ma}_2 \mathrm{~b}_2 \mathrm{~cd}$ complex with suitable figures. |
b)
With suitable illustration explain the theory of Craig and Paddock for pi\pi bonding in
phosphazenes. Give some synthetic routes for polyphosphazenes.
With suitable illustration explain the theory of Craig and Paddock for pi bonding in
phosphazenes. Give some synthetic routes for polyphosphazenes.| With suitable illustration explain the theory of Craig and Paddock for $\pi$ bonding in |
| :— |
| phosphazenes. Give some synthetic routes for polyphosphazenes. |
3.
a)
Explain the concept of hapticity giving suitable examples.
b)
What is beta\beta-elimination in organometallic chemistry? What is the role of agnostic alkyls
in beta\beta-elimination?
What is beta-elimination in organometallic chemistry? What is the role of agnostic alkyls
in beta-elimination?| What is $\beta$-elimination in organometallic chemistry? What is the role of agnostic alkyls |
| :— |
| in $\beta$-elimination? |
4.
a)
With suitable examples explain fluxional organometallic compounds. What are the
probable of symmetric and semibridging carbonyls. Give suitable examples.
With suitable examples explain fluxional organometallic compounds. What are the
probable of symmetric and semibridging carbonyls. Give suitable examples.| With suitable examples explain fluxional organometallic compounds. What are the |
| :— |
| probable of symmetric and semibridging carbonyls. Give suitable examples. |
b)
Determine the number and symmetry designations of the infrared-active C-O modes in the
following derivatives of Mo(CO)_(6)\mathrm{Mo}(\mathrm{CO})_6.
Determine the number and symmetry designations of the infrared-active C-O modes in the
following derivatives of Mo(CO)_(6).
Mo(CO)_(5)PR_(3),cis- Mo(CO)_(4)(PR_(3))_(2),trans- MO(CO)_(4)(PR_(3))_(2),fac-Mo(CO))_(3)(PR_(3))_(3)| Determine the number and symmetry designations of the infrared-active C-O modes in the |
| :— |
| following derivatives of $\mathrm{Mo}(\mathrm{CO})_6$. |
| $\mathrm{Mo}(\mathrm{CO})_5 \mathrm{PR}_3$ cis- $\mathrm{Mo}(\mathrm{CO})_4\left(\mathrm{PR}_3\right)_2$ <br> trans- $\mathrm{MO}(\mathrm{CO})_4\left(\mathrm{PR}_3\right)_2$ fac-Mo(CO)$)_3\left(\mathrm{PR}_3\right)_3$ |
5.
a)
With the help of molecular orbital theory explain the geometry of the nitrosyl ligand.
b)
What are the polydentate phosphines? How do you prepare molybdenocene.
1. a) “Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth,
fifth and sixth periods with proper illustration.”
b) “Explain periodic variation of electronegativity with atomic number for the first six rows
of the periodic table.”
2 . a) “What are the possible molecular structures of xenon hexafluoride? Explain with suitable
figures. Explain the geometrical isomers of Ma_(2)b_(2)cd complex with suitable figures.”
b) “With suitable illustration explain the theory of Craig and Paddock for pi bonding in
phosphazenes. Give some synthetic routes for polyphosphazenes.”
3. a) Explain the concept of hapticity giving suitable examples.
b) “What is beta-elimination in organometallic chemistry? What is the role of agnostic alkyls
in beta-elimination?”
4. a) “With suitable examples explain fluxional organometallic compounds. What are the
probable of symmetric and semibridging carbonyls. Give suitable examples.”
b) “Determine the number and symmetry designations of the infrared-active C-O modes in the
following derivatives of Mo(CO)_(6).
Mo(CO)_(5)PR_(3),cis- Mo(CO)_(4)(PR_(3))_(2),trans- MO(CO)_(4)(PR_(3))_(2),fac-Mo(CO))_(3)(PR_(3))_(3)”
5. a) With the help of molecular orbital theory explain the geometry of the nitrosyl ligand.
b) What are the polydentate phosphines? How do you prepare molybdenocene.| 1. | a) | Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth, <br> fifth and sixth periods with proper illustration. |
| :—: | :—: | :—: |
| | b) | Explain periodic variation of electronegativity with atomic number for the first six rows <br> of the periodic table. |
| 2 . | a) | What are the possible molecular structures of xenon hexafluoride? Explain with suitable <br> figures. Explain the geometrical isomers of $\mathrm{Ma}_2 \mathrm{~b}_2 \mathrm{~cd}$ complex with suitable figures. |
| | b) | With suitable illustration explain the theory of Craig and Paddock for $\pi$ bonding in <br> phosphazenes. Give some synthetic routes for polyphosphazenes. |
| 3. | a) | Explain the concept of hapticity giving suitable examples. |
| | b) | What is $\beta$-elimination in organometallic chemistry? What is the role of agnostic alkyls <br> in $\beta$-elimination? |
| 4. | a) | With suitable examples explain fluxional organometallic compounds. What are the <br> probable of symmetric and semibridging carbonyls. Give suitable examples. |
| | b) | Determine the number and symmetry designations of the infrared-active C-O modes in the <br> following derivatives of $\mathrm{Mo}(\mathrm{CO})_6$. <br> $\mathrm{Mo}(\mathrm{CO})_5 \mathrm{PR}_3$ cis- $\mathrm{Mo}(\mathrm{CO})_4\left(\mathrm{PR}_3\right)_2$ <br> trans- $\mathrm{MO}(\mathrm{CO})_4\left(\mathrm{PR}_3\right)_2$ fac-Mo(CO)$)_3\left(\mathrm{PR}_3\right)_3$ |
| 5. | a) | With the help of molecular orbital theory explain the geometry of the nitrosyl ligand. |
| | b) | What are the polydentate phosphines? How do you prepare molybdenocene. |
{:[6.,” a) “,” Give the structures of (a) “B_(7)H_(7)^(2-)” (b) “B_(5)H_(5)^(4-).],[,” b) “,” What are Wade’s Rule? Apply them to any metalloborane. “],[7.,” a) “,” Explain the different types of compounds having multiple metal-metal bonds. “],[,” b) “,{:[” If pairing energy “P” for “Fe^(3+)” ion is “29”,”875cm^(-1)” and “Delta _(O)” for “[Fe(H_(2)O)_(6)]^(3+)” is “13”,”700cm^(-1)”,”” find out “],[” (i) whether the complex is high spin or low spin “],[” (ii) the number of unpaired electrons “],[” (iii) whether the complex is coloured or not? “]:}],[8.,” a) “,{:[” Give the octahedral as well as tetrahedral field electronic configuration for “Cr^(3+)” and “Co^(3+)” ions. “],[” Which site will be preferred by these ions, octahedral or tetrahedral? Justify your answer. “]:}]:}\begin{array}{|l|l|l|}
\hline 6 . & \text { a) } & \text { Give the structures of (a) } \mathrm{B}_7 \mathrm{H}_7^{2-} \text { (b) } \mathrm{B}_5 \mathrm{H}_5^{4-} . \\
\hline & \text { b) } & \text { What are Wade’s Rule? Apply them to any metalloborane. } \\
\hline 7 . & \text { a) } & \text { Explain the different types of compounds having multiple metal-metal bonds. } \\
\hline & \text { b) } & \begin{array}{l}
\text { If pairing energy } P \text { for } \mathrm{Fe}^{3+} \text { ion is } 29,875 \mathrm{~cm}^{-1} \text { and } \Delta_O \text { for }\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+} \text { is } 13,700 \mathrm{~cm}^{-1}, \text { find out } \\
\text { (i) whether the complex is high spin or low spin } \\
\text { (ii) the number of unpaired electrons } \\
\text { (iii) whether the complex is coloured or not? }
\end{array} \\
\hline 8 . & \text { a) } & \begin{array}{l}
\text { Give the octahedral as well as tetrahedral field electronic configuration for } \mathrm{Cr}^{3+} \text { and } \mathrm{Co}^{3+} \text { ions. } \\
\text { Which site will be preferred by these ions, octahedral or tetrahedral? Justify your answer. }
\end{array} \\
\hline
\end{array}
b)
Explain the Curie Law and Curie-Weiss Law along with their plots.
9.
a)
With suitable illustration explain the super exchange mechanism in dd-metal complexes.
b)
Write the Russell-Saunders terms symbols for states with the angular momentum quantum
Write the Russell-Saunders terms symbols for states with the angular momentum quantum
numbers (L,S)(:} (a) (0,(5)/(2)),(b)(3,(3)/(2)),(c)(2,(1)/(2)),(d),(1,1)| Write the Russell-Saunders terms symbols for states with the angular momentum quantum |
| :— |
| numbers $(\mathrm{L}, \mathrm{S})\left(\right.$ (a) $\left(0, \frac{5}{2}\right),(\mathrm{b})\left(3, \frac{3}{2}\right),(\mathrm{c})\left(2, \frac{1}{2}\right),(\mathrm{d}),(1,1)$ |
10.
a)
[FeF_(6)]^(3-)\left[\mathrm{FeF}_6\right]^{3-} is almost colourless whereas [CoF_(6)]^(3-)\left[\mathrm{CoF}_6\right]^{3-} is coloured and exhibits only a single band in
the visible region of the spectrum. Justify.
[FeF_(6)]^(3-) is almost colourless whereas [CoF_(6)]^(3-) is coloured and exhibits only a single band in
the visible region of the spectrum. Justify.| $\left[\mathrm{FeF}_6\right]^{3-}$ is almost colourless whereas $\left[\mathrm{CoF}_6\right]^{3-}$ is coloured and exhibits only a single band in |
| :— |
| the visible region of the spectrum. Justify. |
b)
Explain charge transfer spectra with suitable examples. What is the reason for the deep purple
colour of the permanganate ion?
Explain charge transfer spectra with suitable examples. What is the reason for the deep purple
colour of the permanganate ion?| Explain charge transfer spectra with suitable examples. What is the reason for the deep purple |
| :— |
| colour of the permanganate ion? |
b) Explain the Curie Law and Curie-Weiss Law along with their plots.
9. a) With suitable illustration explain the super exchange mechanism in d-metal complexes.
b) “Write the Russell-Saunders terms symbols for states with the angular momentum quantum
numbers (L,S)(:} (a) (0,(5)/(2)),(b)(3,(3)/(2)),(c)(2,(1)/(2)),(d),(1,1)”
10. a) “[FeF_(6)]^(3-) is almost colourless whereas [CoF_(6)]^(3-) is coloured and exhibits only a single band in
the visible region of the spectrum. Justify.”
b) “Explain charge transfer spectra with suitable examples. What is the reason for the deep purple
colour of the permanganate ion?”| | b) | Explain the Curie Law and Curie-Weiss Law along with their plots. |
| :— | :— | :— |
| 9. | a) | With suitable illustration explain the super exchange mechanism in $d$-metal complexes. |
| | b) | Write the Russell-Saunders terms symbols for states with the angular momentum quantum <br> numbers $(\mathrm{L}, \mathrm{S})\left(\right.$ (a) $\left(0, \frac{5}{2}\right),(\mathrm{b})\left(3, \frac{3}{2}\right),(\mathrm{c})\left(2, \frac{1}{2}\right),(\mathrm{d}),(1,1)$ |
| 10. | a) | $\left[\mathrm{FeF}_6\right]^{3-}$ is almost colourless whereas $\left[\mathrm{CoF}_6\right]^{3-}$ is coloured and exhibits only a single band in <br> the visible region of the spectrum. Justify. |
| | b) | Explain charge transfer spectra with suitable examples. What is the reason for the deep purple <br> colour of the permanganate ion? |
Expert Answer
Question:-1(a)
Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth, fifth and sixth periods with proper illustration.
Answer:
The metallic radius is a measure of the size of a metal atom in a crystalline lattice. In periodic trends, metallic radii generally increase down a group and decrease across a period. Let’s examine the trends for alkali metals, alkaline earth metals, and transition metals across the fourth, fifth, and sixth periods, along with a proper explanation.
1. Trends in Alkali Metals (Group 1)
Alkali metals have the following elements in the fourth, fifth, and sixth periods:
4th period: Potassium (K)
5th period: Rubidium (Rb)
6th period: Cesium (Cs)
Trend Explanation:
As you move down the group from K to Cs, the metallic radius increases significantly due to the addition of new electron shells.
This increased number of electron shells leads to a larger atomic size, despite the increase in nuclear charge because the added inner electron shells shield the outermost electron from the nucleus’s pull.
Radii values (in pm):
Potassium (K): 227 pm
Rubidium (Rb): 248 pm
Cesium (Cs): 265 pm
General trend for alkali metals: Increasing metallic radius down the group.
2. Trends in Alkaline Earth Metals (Group 2)
Alkaline earth metals have the following elements in the fourth, fifth, and sixth periods:
4th period: Calcium (Ca)
5th period: Strontium (Sr)
6th period: Barium (Ba)
Trend Explanation:
Similar to alkali metals, the metallic radius increases as you move down the group from Ca to Ba. This is due to the addition of electron shells, leading to a larger atomic size.
Again, the increase in nuclear charge is compensated by the shielding effect of inner electrons, causing the metallic radius to increase.
Radii values (in pm):
Calcium (Ca): 197 pm
Strontium (Sr): 215 pm
Barium (Ba): 222 pm
General trend for alkaline earth metals: Increasing metallic radius down the group, but the increase is slightly less pronounced compared to alkali metals.
3. Trends in Transition Metals (Groups 3-12)
Transition metals show more complex behavior due to their d-electrons. In the fourth, fifth, and sixth periods, the following transition metals are typical representatives:
Across the period (left to right): Transition metals show a slight decrease in metallic radii due to increasing nuclear charge, which pulls electrons closer to the nucleus. However, the addition of d-electrons introduces extra electron-electron repulsion, which moderates the decrease.
Down a group: As we move down the group (from the 4th period to the 6th period), the metallic radii increase due to the addition of electron shells, but the increase is not as significant as in alkali or alkaline earth metals because of the lanthanide contraction. This effect reduces the size of 6th-period transition metals compared to what would be expected.
Radii values for some representative transition metals (in pm):
Scandium (Sc): 162 pm
Yttrium (Y): 180 pm
Hafnium (Hf): 159 pm
Iron (Fe): 126 pm
Ruthenium (Ru): 134 pm
Osmium (Os): 135 pm
Copper (Cu): 128 pm
Silver (Ag): 144 pm
Gold (Au): 144 pm
General trend for transition metals:
Across a period: Slight decrease in metallic radii.
Down a group: Slight increase in metallic radii, but affected by the lanthanide contraction in the sixth period.
Graphical Illustration
Summary of the trends with illustrative comparisons:
Alkali Metals: Metallic radius increases from K to Cs (fourth to sixth period).
Alkaline Earth Metals: Metallic radius increases from Ca to Ba, but less sharply than alkali metals.
Transition Metals: Metallic radius decreases across a period and increases slightly down the group, with a significant effect of the lanthanide contraction on the sixth-period transition metals.
The chart above illustrates the trends in metallic radii for alkali metals (K, Rb, Cs), alkaline earth metals (Ca, Sr, Ba), and transition metals (Sc, Y, Hf; Fe, Ru, Os; Cu, Ag, Au) across the fourth, fifth, and sixth periods.
Key observations from the graph:
Alkali Metals (K, Rb, Cs): The metallic radius increases significantly as we move down the group from potassium (K) to cesium (Cs).
Alkaline Earth Metals (Ca, Sr, Ba): The increase in metallic radius is present but less pronounced than in alkali metals.
Transition Metals: The radii decrease slightly across the periods but show moderate increases down the group, especially in the 6th period where the lanthanide contraction affects the trend.
This visual representation highlights the differences in trends among these groups of metals.
Question:-1(b)
Explain periodic variation of electronegativity with atomic number for the first six rows of the periodic table.
Answer:
Electronegativity is the tendency of an atom to attract electrons in a chemical bond. It varies across the periodic table in a predictable manner. Below is an explanation of how electronegativity changes with atomic number for the first six periods of the periodic table:
General Trends in Electronegativity:
Across a Period (Left to Right): Electronegativity generally increases across a period. This is because the nuclear charge increases, pulling the bonding electrons closer to the nucleus without significant additional shielding. As a result, elements become more electronegative.
Down a Group (Top to Bottom): Electronegativity decreases as we move down a group. This occurs because atomic size increases (due to the addition of electron shells), which leads to a weaker attraction for bonding electrons by the nucleus.
Periodic Variation of Electronegativity for the First Six Periods
Period 1 (H, He):
Hydrogen (H) has an electronegativity of 2.20.
Helium (He), being a noble gas with a complete outer shell, doesn’t form bonds easily, so electronegativity is typically not assigned.
Period 2 (Li to Ne):
Lithium (Li) has the lowest electronegativity (1.00), being a Group 1 metal with a strong tendency to lose electrons.
Fluorine (F), at the far right of the period, has the highest electronegativity (3.98), making it the most electronegative element in the periodic table. This is due to its small atomic size and strong effective nuclear charge.
Electronegativity trend: Increases from left to right, starting from lithium (1.00) and moving to fluorine (3.98), with oxygen and nitrogen also being highly electronegative.
Period 3 (Na to Ar):
Sodium (Na) has a low electronegativity (0.93), similar to lithium.
Chlorine (Cl), at the far right, has a much higher electronegativity (3.16), just slightly lower than fluorine.
Electronegativity trend: Increases across the period from Na (0.93) to Cl (3.16), with sulfur (S) and phosphorus (P) showing intermediate values.
Period 4 (K to Kr):
Potassium (K) has a very low electronegativity (0.82), as expected from a Group 1 metal.
Bromine (Br), a halogen, has a high electronegativity (2.96), although slightly lower than chlorine.
Krypton (Kr), being a noble gas, has a full outer electron shell and doesn’t typically form bonds, so it has no significant electronegativity.
Electronegativity trend: Increases across the period from K (0.82) to Br (2.96).
Period 5 (Rb to Xe):
Rubidium (Rb) has a low electronegativity (0.82), similar to potassium.
Iodine (I), a halogen, has a higher electronegativity (2.66), but still lower than bromine and chlorine due to its larger atomic size.
Xenon (Xe), though a noble gas, can sometimes form compounds and is assigned a small electronegativity (2.60), indicating that its reactivity is slightly higher than lighter noble gases.
Electronegativity trend: Increases from Rb (0.82) to I (2.66), with a notable dip for Xenon.
Period 6 (Cs to Rn):
Cesium (Cs) has the lowest electronegativity in the periodic table (0.79), as it strongly tends to lose its valence electron.
Radon (Rn) is similar to xenon and is a noble gas with little tendency to attract electrons, though it may have some reactivity.
Electronegativity trend: Similar to other periods, electronegativity increases from Cs (0.79) to I (around 2.60) before the noble gas radon.
Electronegativity Across the Periods:
Period 1: H (2.20) → He (not typically assigned)
Period 2: Li (1.00) → F (3.98)
Period 3: Na (0.93) → Cl (3.16)
Period 4: K (0.82) → Br (2.96)
Period 5: Rb (0.82) → I (2.66)
Period 6: Cs (0.79) → I (2.66), Rn (noble gas, not typically assigned)
Key Points:
Across each period: Electronegativity increases from left to right due to increasing nuclear charge and a relatively constant shielding effect.
Down each group: Electronegativity decreases due to increased atomic size and more electron shielding, which reduces the attraction between the nucleus and the bonding electrons.
Halogens (F, Cl, Br, I) have high electronegativity values, while alkali metals (Li, Na, K, Rb, Cs) have very low electronegativity values.
Noble gases generally do not form bonds and thus do not have standard electronegativity values, although xenon and radon may have small values due to their ability to form some compounds under specific conditions.
This periodic variation in electronegativity reflects how atoms interact in chemical bonds, with elements on the right side of the periodic table (especially non-metals) being more electronegative than those on the left (metals).
