Group 13 elements (25 Q&A)
Basic Concepts
| No. | Question | Answer |
|---|---|---|
| 1 | Which elements belong to Group 13 of the periodic table? | Boron (B), Aluminium (Al), Gallium (Ga), Indium (In), and Thallium (Tl). |
| 2 | What is the general electronic configuration of Group 13 elements? | $ns^2np^1$ |
| 3 | Why is boron classified as a metalloid? | Boron exhibits both metallic and non-metallic properties. |
| 4 | Why does aluminium have a lower density than expected? | Due to its low atomic mass and high metallic bonding leading to a less compact structure. |
| 5 | Which element in Group 13 shows the highest metallic character? | Thallium (Tl). |
Physical Properties
| 6 | Why does boron have a high melting point? | Due to its strong covalent bonding in the crystalline structure. |
| 7 | Which Group 13 element has the lowest melting point? | Gallium (Ga), because of weak metallic bonding. |
| 8 | What is the oxidation state of Group 13 elements in most compounds? | +3 |
| 9 | Why does thallium show a stable +1 oxidation state? | Due to the inert pair effect. |
| 10 | How does the ionization energy trend vary in Group 13 elements? | It decreases down the group but Ga has slightly higher IE than Al due to poor shielding by d-electrons. |
Chemical Properties & Compounds
| 11 | What happens when boron reacts with acids? | Boron does not react directly with acids due to its non-metallic nature. |
| 12 | Why does Al react with both acids and bases? | Because it is amphoteric in nature. |
| 13 | Write the reaction of aluminium with sodium hydroxide. | $2Al + 2NaOH + 6H_2O \rightarrow 2Na[Al(OH)_4] + 3H_2$ |
| 14 | Which Group 13 oxide is amphoteric? | Aluminium oxide ($Al_2O_3$). |
| 15 | What is the nature of boron trihalides ($BX_3$)? | They are Lewis acids due to the electron-deficient boron. |
| 16 | Why is boric acid considered a Lewis acid? | It accepts a pair of electrons from water molecules. |
| 17 | Give the formula of diborane. | $B_2H_6$. |
| 18 | What is the hybridization of boron in $BF_3$? | $sp^2$ |
| 19 | Why is $BF_3$ more stable than $BI_3$? | Due to strong back bonding in $BF_3$ between boron and fluorine. |
| 20 | What is the structure of diborane ($B_2H_6$)? | It has a three-center two-electron (3c-2e) bond involving hydrogen bridges. |
Miscellaneous
| 21 | Which Group 13 element is used in thermometers for measuring high temperatures? | Gallium (Ga). |
| 22 | What is the role of aluminium powder in thermite reactions? | It acts as a reducing agent to produce molten iron. |
| 23 | Which Group 13 element is used in semiconductors? | Gallium (Ga) in the form of GaAs (Gallium Arsenide). |
| 24 | Why is aluminium corrosion-resistant? | It forms a protective oxide layer on its surface. |
| 25 | Which compound of boron is used as a rocket fuel? | Boron hydrides (e.g., diborane, $B_2H_6$). |
Group 14 elements (25 Q&A)
Basic Concepts & Physical Properties
| 1 | Which elements belong to Group 14 of the periodic table? | Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), and Lead (Pb). |
| 2 | What is the general electronic configuration of Group 14 elements? | $ns^2np^2$ |
| 3 | Why does carbon show allotropy? | Due to its ability to form different structural modifications like diamond, graphite, and fullerenes. |
| 4 | Which is the most metallic element in Group 14? | Lead (Pb). |
| 5 | Why is silicon a semiconductor? | It has an intermediate band gap ($\sim 1.1$ eV), allowing controlled electrical conductivity. |
| 6 | How does atomic size vary down Group 14? | It increases due to the addition of new electron shells. |
| 7 | Why does carbon have the highest ionization energy in Group 14? | Due to its small atomic size and strong effective nuclear charge. |
| 8 | Why does lead show a stable +2 oxidation state? | Due to the inert pair effect. |
| 9 | Which element in Group 14 has the highest melting point? | Carbon (as diamond), due to its strong covalent bonding. |
| 10 | How does the catenation tendency vary in Group 14 elements? | C > Si > Ge > Sn > Pb (decreases down the group). |
Chemical Properties & Compounds
| 11 | What happens when carbon reacts with oxygen? | It forms $CO_2$ or $CO$ depending on oxygen availability. $C + O_2 \rightarrow CO_2$ $2C + O_2 \rightarrow 2CO$ |
| 12 | What is the hybridization of carbon in methane ($CH_4$)? | $sp^3$ |
| 13 | Why is $CO_2$ a gas while $SiO_2$ is a solid? | $CO_2$ has discrete molecules, while $SiO_2$ has a giant covalent network. |
| 14 | Write the reaction of lead dioxide with hydrochloric acid. | $PbO_2 + 4HCl \rightarrow PbCl_2 + Cl_2 + 2H_2O$ |
| 15 | What happens when tin reacts with nitric acid? | It forms metastannic acid ($H_2SnO_3$). |
| 16 | What is the structure of graphite? | Hexagonal layers with delocalized $\pi$-electrons, making it a good conductor. |
| 17 | Why does diamond not conduct electricity? | Due to the absence of free electrons, as all valence electrons are involved in covalent bonding. |
| 18 | What is the nature of $CO_2$ in water? | Weakly acidic, forming carbonic acid ($H_2CO_3$). |
| 19 | What is the hybridization of silicon in $SiCl_4$? | $sp^3$ |
| 20 | Why is lead (II) chloride sparingly soluble in water? | Due to its strong lattice energy. |
Applications
| 21 | Which compound of silicon is used in waterproofing? | Silicones (Polysiloxanes). |
| 22 | Which oxide of lead is used in storage batteries? | Lead dioxide ($PbO_2$). |
| 23 | Why is germanium used in transistors? | Due to its semiconductor properties. |
| 24 | What is the commercial use of silica ($SiO_2$)? | Glass manufacturing. |
| 25 | Why is tin used for coating food cans? | It is corrosion-resistant and non-toxic. |
Group 15 elements (25 Q&A)
Basic Concepts & Physical Properties
| 1 | Which elements belong to Group 15 of the periodic table? | Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb), and Bismuth (Bi). |
| 2 | What is the general electronic configuration of Group 15 elements? | $ns^2np^3$ |
| 3 | Why does nitrogen exist as a diatomic molecule ($N_2$)? | Due to its small size and strong triple bond between nitrogen atoms. |
| 4 | Which is the most metallic element in Group 15? | Bismuth (Bi). |
| 5 | Why does nitrogen show catenation less than phosphorus? | Due to weak N-N single bonds caused by strong lone pair-lone pair repulsions. |
| 6 | How does atomic size vary down Group 15? | It increases due to the addition of new electron shells. |
| 7 | Why does nitrogen have the highest ionization energy in Group 15? | Due to its small atomic size and strong nuclear attraction. |
| 8 | Which element in Group 15 is a liquid at room temperature? | None; however, white phosphorus melts at a low temperature ($\sim 44^\circ\text{C}$). |
| 9 | What is the trend of electronegativity in Group 15? | $N > P > As > Sb > Bi$. |
| 10 | Why does nitrogen have a low boiling point? | Because it exists as a small diatomic gas with weak van der Waals forces. |
Chemical Properties & Compounds
| 11 | What is the common oxidation state of Group 15 elements? | -3, +3, and +5. |
| 12 | Why is the +5 oxidation state of bismuth less stable? | Due to the inert pair effect. |
| 13 | What happens when phosphorus reacts with oxygen? | It forms phosphorus oxides: $4P + 5O_2 \rightarrow 2P_2O_5$ |
| 14 | Why does nitrogen form strong hydrogen bonds in compounds like ammonia? | Due to its high electronegativity and small size. |
| 15 | Write the reaction of ammonia with HCl. | $NH_3 + HCl \rightarrow NH_4Cl$ |
| 16 | Why is white phosphorus more reactive than red phosphorus? | Due to its strained $P_4$ tetrahedral structure. |
| 17 | What is the hybridization of nitrogen in ammonia ($NH_3$)? | $sp^3$ |
| 18 | Why is phosphine ($PH_3$) a weaker base than ammonia? | Due to the lower electronegativity and larger size of phosphorus. |
| 19 | What happens when nitric acid decomposes? | It forms nitrogen dioxide ($NO_2$), oxygen, and water. |
| 20 | Which oxide of nitrogen is neutral? | Nitrous oxide ($N_2O$). |
Applications
| 21 | Which allotrope of phosphorus is used in safety matches? | Red phosphorus. |
| 22 | Which compound of nitrogen is used as a fertilizer? | Ammonium nitrate ($NH_4NO_3$). |
| 23 | Why is nitric acid a strong oxidizing agent? | Due to the presence of the $NO_3^-$ ion, which readily accepts electrons. |
| 24 | Which Group 15 element is used in semiconductors? | Arsenic (As) in gallium arsenide ($GaAs$). |
| 25 | What happens when ammonia is oxidized in the presence of a catalyst? | It forms nitric oxide ($NO$), a key step in Ostwald’s process: $4NH_3 + 5O_2 \rightarrow 4NO + 6H_2O$ |
Group 16 elements (25 Q&A)
Basic Concepts & Physical Properties
| 1 | Which elements belong to Group 16 of the periodic table? | Oxygen (O), Sulfur (S), Selenium (Se), Tellurium (Te), and Polonium (Po). |
| 2 | What is the general electronic configuration of Group 16 elements? | $ns^2np^4$ |
| 3 | What is the common oxidation state of Group 16 elements? | -2, +4, and +6 |
| 4 | Why does oxygen show a maximum oxidation state of +2 while others show +6? | Due to the absence of d-orbitals in oxygen. |
| 5 | Which Group 16 element is a metalloid? | Tellurium (Te). |
| 6 | How does atomic size vary down Group 16? | It increases due to the addition of new electron shells. |
| 7 | Which is the most electronegative element in Group 16? | Oxygen (O). |
| 8 | Why does oxygen have a much lower melting point than sulfur? | Oxygen exists as $O_2$ molecules with weak van der Waals forces, while sulfur exists as $S_8$ rings with stronger intermolecular forces. |
| 9 | Why does the metallic character increase down the group? | Due to decreasing ionization energy and increasing atomic size. |
| 10 | Which is the most stable oxidation state of polonium? | +4 |
Chemical Properties & Compounds
| 11 | Why is the -2 oxidation state more common in oxygen than in other Group 16 elements? | Due to its high electronegativity and small size. |
| 12 | What is the hybridization of sulfur in $SO_2$? | $sp^2$ |
| 13 | Write the reaction of oxygen with hydrogen. | $2H_2 + O_2 \rightarrow 2H_2O$ |
| 14 | Why does sulfur show catenation more than oxygen? | Due to stronger S-S bonds compared to weaker O-O bonds. |
| 15 | What happens when sulfur dioxide is dissolved in water? | It forms sulfurous acid: $SO_2 + H_2O \rightarrow H_2SO_3$ |
| 16 | Why is hydrogen peroxide ($H_2O_2$) a good oxidizing agent? | Due to the presence of an unstable O-O bond that easily breaks to release oxygen. |
| 17 | What happens when sulfur reacts with oxygen? | It forms sulfur dioxide: $S + O_2 \rightarrow SO_2$ |
| 18 | What is the hybridization of sulfur in $SF_6$? | $sp^3d^2$ |
| 19 | Why is $H_2S$ a weaker acid than $H_2Te$? | Because the bond strength decreases down the group, making it easier for $H_2Te$ to donate protons. |
| 20 | Why does $O_3$ act as an oxidizing agent? | Due to the easy decomposition of ozone into oxygen and nascent oxygen ($O_3 \rightarrow O_2 + O$). |
Applications
| 21 | Which compound of sulfur is used in vulcanization of rubber? | Sulfur ($S_8$). |
| 22 | What is the industrial process for manufacturing sulfuric acid? | Contact Process. |
| 23 | Which Group 16 element is used in xerography? | Selenium (Se). |
| 24 | Why is polonium highly radioactive? | Due to its unstable nucleus, which undergoes radioactive decay. |
| 25 | Why is sulfur dioxide used as a food preservative? | It acts as an antimicrobial and antioxidant agent. |
Group 17 elements (25 Q&A)
Basic Concepts & Physical Properties
| 1 | Which elements belong to Group 17 of the periodic table? | Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). |
| 2 | What is the general electronic configuration of Group 17 elements? | $ns^2np^5$ |
| 3 | Why are Group 17 elements called halogens? | The term "halogen" means "salt-former" because these elements form salts with metals. |
| 4 | Which is the most electronegative element in Group 17? | Fluorine (F). |
| 5 | Why does fluorine not show a positive oxidation state? | Due to its high electronegativity and the absence of d-orbitals. |
| 6 | How does atomic size vary down Group 17? | It increases from fluorine to astatine due to the addition of electron shells. |
| 7 | Which halogen exists as a liquid at room temperature? | Bromine ($Br_2$). |
| 8 | How does the boiling point of halogens vary down the group? | It increases due to stronger van der Waals forces. |
| 9 | What is the physical state of fluorine and chlorine at room temperature? | Both are gases. |
| 10 | Why does fluorine have the lowest bond dissociation energy among halogens? | Due to strong interelectronic repulsions in the small $F_2$ molecule. |
Chemical Properties & Compounds
| 11 | What is the common oxidation state of halogens? | -1, but other oxidation states like +1, +3, +5, and +7 are also possible (except for fluorine). |
| 12 | Why is fluorine the strongest oxidizing agent among halogens? | Due to its high electronegativity, low bond dissociation energy, and strong hydration energy. |
| 13 | Write the reaction of chlorine with water. | $Cl_2 + H_2O \rightleftharpoons HCl + HOCl$ |
| 14 | Why is iodine less reactive than chlorine? | Due to its larger atomic size and lower bond dissociation energy. |
| 15 | What happens when bromine reacts with ammonia? | It forms ammonium bromide: $3Br_2 + 8NH_3 \rightarrow 6NH_4Br + N_2$ |
| 16 | Why is hydrogen fluoride ($HF$) a liquid while hydrogen chloride ($HCl$) is a gas? | Due to strong hydrogen bonding in $HF$. |
| 17 | What is the oxidation state of chlorine in hypochlorous acid ($HOCl$)? | +1 |
| 18 | What happens when chlorine reacts with sodium hydroxide at cold temperatures? | It forms sodium hypochlorite ($NaOCl$): $Cl_2 + 2NaOH \rightarrow NaCl + NaOCl + H_2O$ |
| 19 | What is the hybridization of iodine in $IF_7$? | $sp^3d^3$ |
| 20 | Why does fluorine not form $FCl_3$ like chlorine forms $ClF_3$? | Due to the absence of d-orbitals in fluorine. |
Applications
| 21 | Which halogen is used in water purification? | Chlorine ($Cl_2$). |
| 22 | Which halogen is essential for thyroid function? | Iodine ($I_2$), in the form of iodide ions. |
| 23 | What is the industrial method for preparing chlorine? | Electrolysis of brine (Chlor-alkali process). |
| 24 | Which halogen is used in non-stick cookware coatings? | Fluorine (in the form of Teflon, $(C_2F_4)_n$). |
| 25 | Why is fluorine stored in metal cylinders coated with nickel? | Because it reacts with glass and most metals. |
Group 18 elements (25 Q&A)
Basic Concepts & Physical Properties
| 1 | Which elements belong to Group 18 of the periodic table? | Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). |
| 2 | What is the general electronic configuration of Group 18 elements? | $ns^2np^6$ (except Helium: $1s^2$). |
| 3 | Why are Group 18 elements called noble gases? | Because they are chemically inert due to their completely filled valence shell. |
| 4 | Which noble gas has the smallest atomic size? | Helium (He). |
| 5 | Which noble gas is radioactive? | Radon (Rn). |
| 6 | How does atomic size vary down the Group 18 elements? | It increases due to the addition of electron shells. |
| 7 | Why do noble gases have very low boiling points? | Due to weak van der Waals forces between atoms. |
| 8 | Which noble gas has the highest ionization energy? | Helium (He). |
| 9 | How does density change down the group? | It increases from helium to radon. |
| 10 | Why do noble gases have high stability? | Because of their completely filled valence orbitals and high ionization energy. |
Chemical Properties & Compounds
| 11 | Why do noble gases show very low reactivity? | Due to their stable electronic configuration and high ionization energy. |
| 12 | Who discovered noble gas compounds? | Neil Bartlett in 1962. |
| 13 | Which noble gas forms the most number of compounds? | Xenon (Xe). |
| 14 | Write the reaction of xenon with fluorine to form xenon hexafluoride. | $Xe + 3F_2 \rightarrow XeF_6$ |
| 15 | What is the oxidation state of xenon in $XeF_4$? | +4 |
| 16 | Why do krypton and xenon form compounds, but argon does not? | Because Kr and Xe have lower ionization energies than argon, making them more reactive. |
| 17 | What is the shape of $XeF_4$ according to VSEPR theory? | Square planar. |
| 18 | Name a noble gas compound used in chemical synthesis. | Xenon hexafluoroplatinate ($Xe[PtF_6]$). |
| 19 | What is the hybridization of xenon in $XeF_6$? | $sp^3d^3$ |
| 20 | Write the hydrolysis reaction of $XeF_4$. | $XeF_4 + 2H_2O \rightarrow XeO_2 + 4HF$ |
Applications
| 21 | Which noble gas is used in filling balloons? | Helium (He). |
| 22 | Which noble gas is used in neon signs? | Neon (Ne). |
| 23 | Why is argon used in welding? | Because it provides an inert atmosphere and prevents oxidation. |
| 24 | Which noble gas is used in cancer treatment? | Radon (Rn), in radiation therapy. |
| 25 | Why is xenon used in high-intensity lamps? | Due to its ability to produce bright white light. |
Compounds of p-block (35 Q&A)
Acidic & Basic Strength
| 1 | Which is more acidic, $H_2O$ or $H_2S$? | $H_2S$ is more acidic due to weaker H-S bonds compared to H-O bonds. |
| 2 | How does acidic strength vary among hydrides of Group 15? | $NH_3 < PH_3 < AsH_3 < SbH_3 < BiH_3$ (Acidic strength increases down the group). |
| 3 | Why is $HF$ a weaker acid than $HCl$ despite fluorine being more electronegative? | Due to strong hydrogen bonding in $HF$, which makes it difficult to dissociate. |
| 4 | Which is more basic, $NH_3$ or $PH_3$? | $NH_3$ is more basic due to the higher electron density on nitrogen. |
| 5 | How does basicity of halide ions change in aqueous solution? | $I^- < Br^- < Cl^- < F^-$ (F⁻ is the most basic due to its small size and high charge density). |
| 6 | Which is more acidic, $HClO$ or $HClO_4$? | $HClO_4$ is more acidic due to higher oxidation state and stronger electron-withdrawing effect. |
| 7 | Why is boric acid considered a weak acid? | It acts as a Lewis acid by accepting $OH^-$ rather than donating $H^+$. |
| 8 | How does the acidic nature of oxides of nitrogen vary? | $N_2O < NO < N_2O_3 < NO_2 < N_2O_5$ (Acidic nature increases with oxidation state). |
| 9 | Why is $CO_2$ acidic while $SiO_2$ is neutral? | $CO_2$ dissolves in water to form carbonic acid, while $SiO_2$ is an acidic oxide but insoluble in water. |
| 10 | Why is $Al(OH)_3$ amphoteric while $NaOH$ is purely basic? | $Al(OH)_3$ reacts with both acids and bases, whereas $NaOH$ only reacts with acids. |
Reducing & Oxidizing Properties
| 11 | Which is a stronger reducing agent, $H_2S$ or $H_2O$? | $H_2S$, because sulfur is less electronegative than oxygen and readily donates electrons. |
| 12 | Why is $HI$ a stronger reducing agent than $HCl$? | Due to the weaker H-I bond, which makes it easier to donate electrons. |
| 13 | Why is $SO_2$ a reducing agent while $SO_3$ is not? | $SO_2$ can be oxidized to $SO_3$, whereas $SO_3$ is already in its highest oxidation state. |
| 14 | How does reducing strength vary among halides? | $F^- < Cl^- < Br^- < I^-$ (Iodide is the strongest reducing agent). |
| 15 | Why does $NH_3$ act as a reducing agent but $NO_2$ acts as an oxidizing agent? | $NH_3$ can donate electrons, while $NO_2$ can accept electrons. |
| 16 | Why is $P_4$ more reactive than $N_2$? | $P_4$ has weaker bonds due to bond strain, while $N_2$ has a strong triple bond. |
| 17 | Why is $ClO_2$ a strong oxidizing agent? | Due to the presence of chlorine in a high oxidation state (+4). |
| 18 | Why is $XeF_6$ a strong fluorinating agent? | Due to the high oxidizing power of xenon in a high oxidation state. |
| 19 | Why is $HNO_3$ a strong oxidizing agent? | Due to the presence of nitrogen in its +5 oxidation state. |
| 20 | Which is a stronger oxidizing agent, $O_2$ or $O_3$? | $O_3$ (ozone) is stronger due to the release of nascent oxygen. |
Amphoteric & Structural Properties
| 21 | Which p-block hydroxide shows amphoteric behavior? | $Al(OH)_3$. |
| 22 | Why is $PbO_2$ amphoteric? | It reacts with both acids and bases to form salts. |
| 23 | Why does $ZnO$ exhibit amphoteric nature? | It reacts with both $HCl$ (acid) and $NaOH$ (base). |
| 24 | Which oxide is more amphoteric, $Al_2O_3$ or $B_2O_3$? | $Al_2O_3$, as $B_2O_3$ is predominantly acidic. |
| 25 | Why is $Sn(OH)_2$ amphoteric? | It can react with both acids and bases. |
| 26 | Why is the bond length of $H-F$ shorter than $H-I$? | Due to the smaller atomic radius of fluorine. |
| 27 | Why is the bond angle in $H_2O$ less than in $NH_3$? | Due to stronger lone pair repulsions in $H_2O$. |
| 28 | Why does the bond length of halogens increase down the group? | Due to increasing atomic size. |
| 29 | Why is the bond angle in $ClO_2^-$ less than in $NO_2^-$? | Due to greater lone pair repulsions in $ClO_2^-$. |
| 30 | Why is the bond length of $NO$ shorter than $NO_2$? | Due to partial double bond character in $NO$. |
| 31 | Why is $H_2O$ liquid while $H_2S$ is a gas? | Due to strong hydrogen bonding in water. |
| 32 | Why is $HF$ more viscous than $HCl$? | Due to extensive hydrogen bonding. |
| 33 | Why is $SiH_4$ less stable than $CH_4$? | Due to weaker Si-H bonds. |
| 34 | Why does $N_2$ have a triple bond? | Due to effective p-p orbital overlap. |
| 35 | Why is $XeF_2$ linear in shape? | Due to sp³d hybridization and lone pair repulsions. |
Exceptions in p-block (25 Q&A)
Electronic & Oxidation Exceptions
| 1 | Why does boron have an incomplete octet in BF₃? | Boron has only 6 valence electrons after bonding, making it electron-deficient. |
| 2 | Why does aluminum form AlCl₃ instead of AlCl? | Due to the higher stability of $Al^{3+}$ over $Al^+$. |
| 3 | Why does nitrogen not form pentahalides like PCl₅? | Nitrogen lacks vacant d-orbitals, restricting it to a maximum oxidation state of +3. |
| 4 | Why is the bond angle in NH₃ greater than in PH₃? | NH₃ has stronger lone pair-bond pair repulsions due to higher electronegativity of N. |
| 5 | Why is O₂ a paramagnetic molecule despite having an even number of electrons? | Due to the presence of unpaired electrons in its antibonding molecular orbitals. |
| 6 | Why does fluorine show only a -1 oxidation state? | Fluorine is the most electronegative element and lacks d-orbitals. |
| 7 | Why does oxygen show a +2 oxidation state in OF₂? | Because fluorine is more electronegative, forcing oxygen into a positive oxidation state. |
| 8 | Why does Pb exhibit +2 oxidation state more commonly than +4? | Due to the inert pair effect, which stabilizes the lower oxidation state. |
| 9 | Why does Cl exhibit a +7 oxidation state in HClO₄ but not F? | Chlorine has vacant d-orbitals, while fluorine lacks them. |
| 10 | Why is +3 oxidation state more stable in Tl (Thallium) than +1? | Actually, +1 is more stable due to the inert pair effect. |
Bonding & Reactivity Exceptions
| 11 | Why is B₂H₆ (diborane) an exception in bonding? | It has three-center two-electron (3c-2e) bonds instead of normal two-electron bonds. |
| 12 | Why does diamond have a high melting point despite being covalent? | Due to its strong 3D network of covalent sp³ bonds. |
| 13 | Why is graphite a good conductor of electricity while diamond is not? | Graphite has delocalized $\pi$-electrons due to sp² hybridization. |
| 14 | Why does SF₄ have a see-saw shape instead of tetrahedral? | Due to the presence of a lone pair on sulfur. |
| 15 | Why does XeF₂ have a linear shape despite sp³d hybridization? | Due to the presence of three lone pairs on xenon, which occupy equatorial positions. |
| 16 | Why is boric acid considered a Lewis acid despite being a weak acid? | It accepts $OH^-$ instead of donating $H^+$. |
| 17 | Why is HF a weaker acid in water but a stronger acid in non-aqueous solvents? | Due to extensive hydrogen bonding in water, reducing its dissociation. |
| 18 | Why does HNO₃ act as both an acid and an oxidizing agent? | It donates $H^+$ and also contains nitrogen in a high oxidation state (+5), making it an oxidizer. |
| 19 | Why is H₂O liquid while H₂S is a gas? | Due to strong hydrogen bonding in water. |
| 20 | Why does SiO₂ behave as an acidic oxide while CO₂ behaves as a gas? | SiO₂ forms a strong covalent network, while CO₂ exists as discrete molecules. |
| 21 | Why does F₂ have lower bond dissociation energy than Cl₂ despite being smaller? | Due to strong lone pair-lone pair repulsions in fluorine. |
| 22 | Why does white phosphorus ($P_4$) ignite in air while red phosphorus does not? | White phosphorus is more reactive due to strain in the $P_4$ tetrahedral structure. |
| 23 | Why is noble gas xenon able to form compounds while helium and neon do not? | Due to lower ionization energy and available d-orbitals in xenon. |
| 24 | Why is H₂O₂ unstable and decomposes easily? | Due to weak O-O bond and high tendency to form $O_2$ and $H_2O$. |
| 25 | Why does ClF₃ exist but not FCl₃? | Because fluorine cannot expand its octet due to the absence of d-orbitals. |
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