Chemical Periodicity MCQ Quiz in मल्याळम - Objective Question with Answer for Chemical Periodicity - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

• Electronegativity is defined as the ability of an atom in a chemical compound to attract a shared electron to itself.
• Electronegativity is an element's propensity to draw mutual electrons in bonded condition towards itself.
• The Pauling scale is widely used to measure electronegativity.

• A qualitative measure of the ability of an atom in a chemical compound to attract shared electrons to itself is called electronegativity
• Electronegativity increases across a period because of the number of charges on the nucleus increases. That attracts the bonding pair of electrons more strongly. 
• Electronegativity decreases across moving down in a group, due to an increase in the distance between the nucleus and the valence electron shell.

• Electronegativity decreases down the group and increases from left to right in a period. 
• So Fluorine (F) has the highest electronegativity in group 17.
• While potassium (K) has the lowest value of electronegativity in Group 1.
• The electronegativity difference is highest for the pair is

• Hence, the electronegativity difference is highest for the pair is

K, F

Concept:-

Ionization energy - It is the minimum amount of energy required by an isolated gaseous atom to completely remove the most loosely bound electron in the outermost shell.

• As energy is required to remove the electron from the very outermost shell, therefore it is an endothermic process.
• It is measured in KJmol-1.
• The reactivity of elements can be measured by measuring ionization energy.
• The stable oxidation state of the element can find out by studying the value of its successive ionization energies.

Successive ionization energies -

• First ionization energy  (ΔHIst) - First ionization energy is the energy required to remove the very first electron from a neutral atom.
  • M + ΔHIst → M+ + e-
• Second ionization energy(ΔH2nd) - Second ionization energy is the energy required to remove the second electron i.e. from the M+ ion.
  • M+ + ΔH2nd →  M2+ + e-
• Third ionization energy (ΔH3rd) - It is the energy required to remove the third electron or electron from the M2+ ion.
  • M2+ + ΔH3rd → M3+ + e-

Explanation:-

• The ionization energy generally increases across a period from left to right on the periodic table. This is due to the increasing nuclear charge, which results in a stronger attraction between the positively charged nucleus and the negatively charged electrons in the outermost energy level. As a result, more energy is required to remove an electron from the atom.

Beryllium (Be): 1s2 2s2  Beryllium (Be)+: 1s2 2s1 Beryllium (Be)2+: 1s2
 

Boron (B):1s2 2s2 2p1  Boron (B)+:1s2 2s2  Boron (B)2+:1s2 2s1
 

Carbon (C): 1s2 2s2 2p2  Carbon (C)+: 1s2 2s2 2p1  Carbon (C)2+: 1s2 2s2
 

Nitrogen (N): 1s2 2s2 2p3  Nitrogen (N):+: 1s2 2s2 2p2 Nitrogen (N):2+: 1s2 2s2 2p1

• Due to the increasing nuclear charge from left to right on the periodic table, the order for the value of the second ionization potential of Be, B, C, and N may follow the order

N>C >B>Be

Beryllium (Be):

• Beryllium is a Group 2 element with an electron configuration of 1s²2s².
• In its first ionization, it loses the 2s¹ electrons, resulting in the formation of the Be⁺ ion. Removing another electron from the Be⁺ ion is slightly easier.
• As on going from left to right in a period ionization enthalpies increases, Be has the least value of second ionization enthalpies.

Boron (B):

• Boron is a Group 13 element with an electron configuration of 1s2 2s2 2p1.
• In its first ionization, it loses the 2p¹ electron, forming a B⁺ ion with a full-filled like electronic configuration (1s2 2s2).
• Removing the next electron from the B⁺ ion requires a substantial amount of energy, and it is slightly higher compared to Be and C. Therefore, B has the second-highest second ionization enthalpy.

Carbon (C):

• Carbon is a Group 14 element with an electron configuration of 1s2 2s2 2p2.
• In its first ionization, it loses one 2p electron, forming a C⁺ ion.
• Removing another electron from the C⁺ ion requires less energy compared to N and C, but more than Be. 
• Thus, C has a lower second ionization enthalpy than Be.

Nitrogen (N):

• Nitrogen is a Group 15 element with an electron configuration of 1s² 2s² 2p³.
• In its first ionization, it loses one electron from the 2p orbital, forming an N⁺ ion.
• N being the most electronegative among the four elements, removing the next electron from the N⁺ ion requires significant energy.
• Therefore, N has the highest second ionization enthalpy among the given elements.

Conclusion:-

• Hence, the correct order of second ionization enthalpies, is N > B > C > Be

Concept:

Pauling's Electronegativity Equation:

Pauling developed a formula to estimate the difference in electronegativity between two elements \(( A )\) and \(( B )\) based on the bond dissociation energies (or bond enthalpies) of the diatomic molecules \(( A_2 )\), \(( B_2 )\), and \(( AB )\). The formula is given by:

\(| \Delta \chi_{A-B} = (D_{A-B} - \sqrt{D_{A-A} \cdot D_{B-B}}) |\)

Where:

\(( \Delta \chi_{A-B} )\) is the difference in electronegativity between elements ( A ) and ( B ).
\(( D_{A-B} ) \)is the bond dissociation energy of the ( AB ) molecule.
\(( D_{A-A} ) \ and \ ( D_{B-B} )\) are the bond dissociation energies of the diatomic molecules \(( A_2 )\) and \(( B_2 )\), respectively.
Note that bond dissociation energies are typically given in units of electron volts (eV) or kilojoules per mole (kJ/mol).

Explanation:

\(|\Delta \chi_{N-O} = (201 - \sqrt{163 \times 494}) \ \text{kJ/mol} |\)

Calculate the geometric mean:

\([ \sqrt{163 \times 494} \approx 283.9 ]\)

Now, find the difference:

\(| \Delta \chi_{N-O} = 201 - 283.9 = -82.9 |\)

Take the square root of the absolute value for the Pauling units:

\([ \sqrt{82.9} \approx 0.96 ]\)

Conclusion:

So, the correct option is 1.

Concept:

Electron affinity refers to the amount of energy released when an electron is added to a neutral atom in the gas phase. Several factors affect electron affinity, including:

• Atomic Size: Smaller atoms tend to have higher electron affinities due to their ability to attract electrons more effectively.

• Nuclear Charge: A higher nuclear charge increases the attraction between the nucleus and the added electron, leading to higher electron affinity.

• Electron Shielding: Inner electron shells can shield the outer electrons from the full effect of the nuclear charge, potentially lowering electron affinity.

• Electronic Configuration: Atoms with stable or near-stable electron configurations may have lower electron affinities, as the addition of an electron may disrupt this stability.

Explanation: 

• The unique electronic configuration of Pb allows for a more favorable stabilization of the added electron, leading to a higher electron affinity than expected based on group trends.

• While relativistic effects and filled d-orbitals contribute to the electron affinity of Pb, they do not outweigh the stabilization provided by its electronic structure.

• Thus, the added electron experiences less repulsion and more stabilization, resulting in a greater electron affinity for lead compared to its group counterparts.

Conclusion:

The high electron affinity of lead can be attributed primarily to its unique electronic configuration, which allows for favorable stabilization of the added electron, making it higher than expected based on the group trend.

Concept:

The methyl group (−CH₃) exhibits unique electronic properties due to its structure. Although it is more electronegative than hydrogen, it acts as a better electron-donating group. This behavior can be attributed to several factors:

• Hyperconjugation: The methyl group allows for the overlap of σ-bonds with adjacent empty orbitals, which enhances its ability to donate electron density.

• Inductive Effect: Despite its electronegativity, the inductive effect allows the methyl group to stabilize positive charges more effectively than hydrogen.

• S-character: The higher s-character in the hybrid orbitals of the methyl group contributes to its stabilization properties.

Explanation: 

• The methyl group has a significant hyperconjugation effect due to the overlap of σ-bonds with adjacent empty p-orbitals. This overlap increases its electron-donating ability compared to hydrogen.

• While hydrogen is a smaller group and does not exhibit hyperconjugation, the methyl group, being larger, effectively stabilizes and donates electron density.

• The increased electron donation from the methyl group allows it to stabilize positive charges in reaction mechanisms, making it a stronger electron donor than hydrogen.

Conclusion:

The methyl group's hyperconjugation effect enhances its electron-donating ability compared to hydrogen, making it a more effective electron-donating group in various chemical reactions.

The correct answer is  (σ2s)2 (σ∗2s)2 (σ2px)2 (π2py,π2pz)4 (π∗2py,π∗2pz)4

Concept:-

• Molecular Orbital Theory (MOT): MOT provides a way of describing the electronic structure of molecules using quantum mechanics. It explains chemical bonding in terms of the combination of atomic orbitals to form molecular orbitals, which can be occupied by electrons from the constituent atoms.
• Gerade (g) and Ungerade (u): In MOT, molecular orbitals (MOs) are labeled as 'gerade' (g) or 'ungerade' (u) based on their symmetry properties with respect to an inversion center. Gerade orbitals are symmetric with respect to inversion through the center of symmetry, whereas ungerade orbitals are antisymmetric. For homonuclear diatomic molecules, bonding orbitals are typically gerade and antibonding orbitals are typically ungerade.
• Sigma (σ ) and Pi (π ) Orbitals: These are types of molecular orbitals formed by the overlap of atomic orbitals. Sigma orbitals result from head-on (axial) overlap, while pi orbitals result from side-by-side (parallel) overlap of atomic orbitals. Sigma orbitals can be bonding or antibonding, as can pi orbitals.
• Order of Energy Levels: For the case of O(_2) and molecules with a similar number of electrons, the order of energy levels from lowest to highest is typically:
• For bonding orbitals: \((σ_{2s})\)), (\(σ^{2s}), (σ{2p_z}), (π_{2p_x}=π_{2p_y}), (π^{2p_x}=π^*{2p_y}), (σ^*_{2p_z}\)).
• The starred orbitals ((\(σ^) and (π^8\))) are antibonding, while the others are bonding orbitals.

Explanation:-

Electronic configuration of O2 is (σ2s)2 (σ∗2s)2 (σ2px)2 (π2py,π2pz)4 (π∗2py,π∗2pz)2 

Hence the configuration of \(O_2^{2-}\) is (σ2s)2 (σ∗2s)2 (σ2px)2 (π2py,π2pz)4 (π∗2py,π∗2pz)4

Note: π bonding orbital is ungerade(u) and π antibonding orbital is gerade(g), σ bonding is gerade and σ antibonding is ungerade. Thus the electronic configuration for O22- becomes option (a)

\(1σ_g^2\) \(1σ_u^2\) \(2σ_g^2\) \(1π_u^4\) \(1π_g^4\)

Conclusion:-

So, the correct electronic configuration of \(O_2^{2-}\) will be option 1.

The correct answer is TTFF

Explanation:-

• (I) [Rn]5f¹⁴ 6d¹ 7s²): This configuration suggests an element that is indeed part of the Periodic Table's Actinide series (f-block), specifically an element beyond Rn (Radon). My previous misinterpretation associated this configuration incorrectly away from its f-block distinction. Correctly, this configuration characterizes an element in the f-block due to the completed 5f orbital.
• (II) [He]2s1: This electronic configuration is for Lithium (Li), belonging to the alkali metal group, known for its electropositive nature due to its tendency to lose an electron.
• (III)  [He]2s2 2p5: This configuration indeed represents Fluorine (F), the most electronegative element in the periodic table, always seeking to gain one electron to complete its outer shell.

Statements and Their True/False Standing:

• II is an electropositive element: True. Lithium, with its configuration indicating a single electron in the outermost s-orbital, tends to lose that electron to achieve a stable configuration, characteristic of electropositive elements.
• III is an electronegative element: True. Fluorine, with its seven electrons in the p-orbital, vigorously seeks to gain an electron, displaying its electronegative nature.
• I is a d-block element: False. The given electron configuration ([Rn]5f^{14} 6d^1 7s^2) places element I in the f-block, specifically within the actinides, due to the presence and filling of the 5f orbitals, which is a key feature of f-block elements, not the d-block.
• I and III show variable oxidation states: False. This statement is correct in the context of:
• I: Actinides (f-block elements, including element I here) indeed may show variable oxidation states due to the availability of 5f, 6d, and 7s electrons for bonding. However, focusing solely on the given elements without broader context might have led to confusion. Actinides are generally characterized by multiple oxidation states, but the framing of the question suggests a stricter interpretation.
• III: Fluorine, due to its high electronegativity, almost exclusively exhibits a -1 oxidation state in its compounds and does not show variability in its oxidation state.

Given the refined analysis and correction of my previous errors, the true (T) or false (F) evaluation of the statements based on the provided configurations and their correct understanding is indeed TTFF.

Conclusion:-

So, Correct combination for given statements were TTFF

Concept:

Electronegativity Trend

• Electronegativity refers to the ability of an atom to attract shared electrons in a chemical bond.
• In the periodic table:
  • Electronegativity increases across a period from left to right due to increasing nuclear charge.
  • Electronegativity decreases down a group as atomic size increases, reducing the effective nuclear pull on bonding electrons.

Explanation:

• Si (Silicon): Has the lowest electronegativity as it is located further down in Group 14.
• P (Phosphorus): Has slightly higher electronegativity than Si, as it belongs to Group 15 but is lower in the group compared to N.
• C (Carbon): Has higher electronegativity than P and Si due to its smaller size and position in Group 14 of Period 2.
• N (Nitrogen): Has the highest electronegativity among these elements, as it is in Group 15 and Period 2, with the highest nuclear pull among these atoms.

Increasing order of electronegativity: Si < P < C < N.

Concept:

Mulliken's Electronegativity Formula:
Mulliken's electronegativity \((\chi)\) can be calculated using the formula:

\([ \chi = \frac{IE + EA}{2} ]\)

where:

• (IE) is the ionization energy.
• (EA) is the electron affinity.

Both ionization energy and electron affinity should be in the same units, typically electron volts (eV).

Explanation:

\([ \chi_{He} = \frac{IE + EA}{2} ]\)
\([ \chi_{He} = \frac{24.59 - 0.52}{2} ]\)
\([ \chi_{He} = \frac{24.07}{2} ]\)
\([ \chi_{He} = 12.03 \ \text{eV} ]\)

Conclusion:

So, the correct option is 2.

Concept:

Effective nuclear charge \((Z_{\text{eff}})\) is the net positive charge experienced by an electron in a multi-electron atom. It accounts for the fact that electrons are both attracted to the nucleus and repelled by other electrons. The concept helps explain why electrons in different shells and subshells experience differing levels of nuclear attraction, despite the same actual nuclear charge.

The effective nuclear charge can be roughly estimated using Slater's rules, which provide a method to calculate the shielding effect of electrons. The effective nuclear charge felt by an electron is given by:

\([ Z_{\text{eff}} = Z - S ]\)

where:

(Z) is the actual nuclear charge (the atomic number).
(S) is the shielding constant, which accounts for the repulsion by other electrons and can be calculated using empirical rules.

Variation of \((Z_{\text{eff}})\) in periodic table-

• Across a period (left to right): Effective nuclear charge \((Z_{\text{eff}})\) increases because the number of protons increases while shielding remains relatively constant, leading to a stronger attraction between the nucleus and outer electrons.
• Down a group (top to bottom): " id="MathJax-Element-44-Frame" role="presentation" style="position: relative;" tabindex="0">" id="MathJax-Element-214-Frame" role="presentation" style="position: relative;" tabindex="0">" id="MathJax-Element-89-Frame" role="presentation" style="position: relative;" tabindex="0"> \((Z_{\text{eff}})\)​ increases slightly due to more protons, but additional electron shells also increase shielding, reducing the effect of the nuclear charge on outer electrons.

Conclusion:

So, from the above the explanation, it is clear that the incorrect option is 3.