S - Block MCQ Quiz in मल्याळम - Objective Question with Answer for S - Block - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept -

Oxides - 

The basic nature of oxides increases down the group and decreases along a period

Oxides are the compound of oxygen with other elements in which the oxidation state of 'O' is -2.

• Oxide is generally an anion of oxygen with oxidation number -2 or simply it is O2-.
• For example; NO, MgO, Na2O, etc.

Oxides are classified into four categories based on their acid-base characteristics. These are - 

1. Acidic oxides 
2. Basic oxides 
3. Amphoteric oxides 
4. Neutral oxides 

Nature of oxides -

Generally,

• Metals form basic oxides because they can donate electrons and non-metals form acidic oxides because they can accept electrons.
• The basic nature of oxides increases down the group and decreases along a period, for ex - MgO, CaO, etc.
• Amphoteric oxides are those which behave as both acidic and basic oxides. They can react with acid as well as the base.  For example - BeO, Al2O3, etc.
• Neutral oxides are neither acidic nor basic. For example - H2O, N2O, CO, etc

Explanation:

→The basic nature of oxides increases down the group and decreases along a period.

→Metals form basic oxides because they can donate electrons and non-metals form acidic oxides because they can accept electrons.

Among the given elements,

• potassium is having most metallic in nature, hence form most basic oxide.
• Na lie before K in group 1, therefore, the oxide of Na is less basic than oxide of K or Na₂O < K₂O.
• In a period, basic nature of oxides decreases therefore, MgO <  Na2O < K2O.
• Oxide of Aluminum is amphoteric in nature as it can react with acid as well as the base and hence 

Al2O3 < MgO < Na2O < K2O.

Conclusion:

Therefore, the set representing the correct increasing order of basic character is, Al2O3 < MgO < Na2O < K2O

Concept:

• Non metals exist in solid liquid and gases state.
• They are all placed in p-block towards right hand side of periodic table from group no 13 to 18.

Explanation:

• Talking about halogen they are placed in group 17
• Member of this family include Fluorine(F) Chlorine (Cl), Bromine(Br), Iodine(I), Astatine(At), and Tennessine(Ts).
• Among these only Br exist in liquid state and F, Cl, exist in gases state while Iodine is a solid.
• As the atomic no. increases the Vander waal force of attraction increases. 
• In case of Br intermolecular forces are strong enough so that it does not evaporate.
• Bromine forms diatomic molecules and Van der Waals interactions are sufficiently strong.
• Also Br is more reactive than Iodine but less reactive than Cl.
• After Br, as we move down the group iodine occur as solid because Vander Waal forces become more stronger than Br and hence physical state become dense.
• We conclude that down the group the physical state become more denser therefore we observed that F, Cl are gases, Br is liquid and I is solid.
• Among other non-metals like Carbon, Sulphur, Phosphorous, etc are solid whereas Oxygen, Nitrogen, are gases.

​

Correct answer: 1)

Concept:

• Carbonates of alkaline earth metals are insoluble in water and can be precipitated by the addition of a sodium or ammonium carbonate solution to a solution of a soluble salt of these metals.
• Solubility of carbonates decreases down the group.
• All the carbonates decompose on heating to give carbon dioxide and oxide.
• Beryllium carbonate is unstable and can be kept only in the atmosphere of CO2.
• The thermal stability of carbonates increases down the group.

Explanation:

• Beryllium carbonate is unstable due to the smaller size of the cation and larger size of the anion (as smaller cation stabilizes smaller anion through crystal lattice energy) and can be kept only in the atmosphere of CO2​.
• The thermal stability increases with increasing cationic size.
• BeCO3
• BeCO3 →BeO+CO2
• Since the decomposition reaction is reversible, therefore, to increase the stability of BeCO3 or to reverse the above equilibrium.
• Thus, kept only in the atmosphere of CO2.
• BeCO3" id="MathJax-Element-2-Frame" role="presentation" style=" position: relative;" tabindex="0">" id="MathJax-Element-32-Frame" role="presentation" style="position: relative;" tabindex="0">  is unstable due to strong polarizing the effect of small Be2+ ion on the large polarisable carbonation.
• Moreover, extra stability of the oxide is achieved through lattice energy by packing small cations with small oxide ions.
• Beryllium carbonate is unstable and can be kept only in the atmosphere of CO2.

Conclusion:

Thus, Beryllium carbonate is unstable and can be kept only in the atmosphere of CO2.

The correct answer is oxygen

Concept:

According to Fajan’s rule, greater the polarizing power of cation greater would be the covalent character.

Fajans' rules is used to predict whether a chemical bond will be covalent or ionic and depend on the charge on the cation and the relative sizes of the cation and anion. All of the alkaline earth metal is reacting with the halogens to form the alkaline earth metal halides.

SinceBe²⁺, has maximum polarizing power among the given cations. Therefore, BeX₂ would be most covalent alkaline earth metal halides among the given halides.

Properties of Halides of Alkali Earth Metals:

All beryllium halides are essentially covalent and are soluble in organic solvents. The halides of all other alkaline earth metals are ionic. Except BeCl₂ all other chlorides of group 2 form hydrates but their tendency to form hydrates decrease.

Concept:

Smaller in size of center atoms more water molecules will crystallize hence Ba(NO₃)₂ is answer due to its largest size of '+ve' ion.

\({\rm{Ba}}{\left( {{\rm{N}}{{\rm{O}}_3}} \right)_2} \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\leftharpoonup\over {\smash{\rightharpoondown}}$}} B{a^{2 + }} + 2NO_3^ - \)

Action of alkali metals with water compounds contain acidic hydrogen reacts readily forming hydroxides with the liberation of hydrogen.

Some of the physical properties of the compound earth metals are:

• They are silverfish, white, and hard metals. They are soft but harder than alkali metals in comparison.
• Some of them appear whitish by beryllium and magnesium appear greyish in colour.
• Their melting and boiling points are higher compared to the alkali metals.
• These metals are strongly electropositive in nature. Alkaline earth metals give a different colour with the flame test such as calcium gives brick red colour, strontium gives crimson colour and barium gives apple green colour, all of which are different for different metals.

Some of chemical properties of the compound earth metals are:

• All alkaline earth metals tend to form monoxide except the metal, beryllium.
• They usually have high electrical and thermal conductivities as they have a metallic bonding.
• The oxides of alkaline earth metal are basic but less basic in comparison to alkali metals.
• Alkali earth metal form solid carbonates. As one move from beryllium to barium thermal stability of carbonated usually increases.

CONCEPT:

Stability of Superoxides (KO₂, RbO₂, CsO₂)

• Superoxides are compounds containing the superoxide anion (O₂^-).
• The stability of superoxides increases with the size of the cation.
• This is due to the lattice energy and the ability of larger cations to stabilize the larger superoxide anion.

EXPLANATION:

• For alkali metal superoxides:
  • KO₂ (Potassium superoxide)
  • RbO₂ (Rubidium superoxide)
  • CsO₂ (Cesium superoxide)
• As we move down the group in the periodic table, the size of the alkali metal cations increases (K⁺ < Rb⁺ < Cs⁺).
• Larger cations better stabilize the superoxide anion, leading to increased stability of the superoxide compound.
• Therefore, the stability order is:
  • KO₂ < RbO₂ < CsO₂

Therefore, the correct stability order of KO₂, RbO₂, CsO₂ is KO₂ < RbO₂ < CsO₂.

CONCEPT:

Density of Elements

• Density is defined as mass per unit volume of a substance. It is an important property that helps in determining how closely packed the atoms or molecules of a substance are.
• The density of elements can vary depending on their atomic structure and the arrangement of atoms in their crystal lattice.

EXPLANATION:

• For the elements Beryllium (Be), Magnesium (Mg), Calcium (Ca), and Strontium (Sr):
  • Generally, in the alkali earth metal group, the density increases down the group.
  • Beryllium, being at the top of the group, has the lowest density, and Strontium, being lower in the group, has a higher density.
    • Beryllium (Be): 1.85
    • Magnesium (Mg): 1.74
    • Calcium (Ca): 1.55
    • Strontium (Sr): 2.64
• From the given densities, the correct order from highest to lowest density is:
  • Strontium (Sr) > Beryllium (Be) > Magnesium (Mg) > Calcium (Ca)

Therefore, the correct order of density of Be, Mg, Ca, Sr is Sr > Be > Mg > Ca, which corresponds to Option 1.

CONCEPT:

Diagonal Relationship in the Periodic Table

• The diagonal relationship refers to the similarity in properties between certain pairs of diagonally adjacent elements in the second and third periods of the periodic table.
• Elements exhibiting a diagonal relationship have similar electronegativities, ionic sizes, and other properties due to the balancing effect of moving diagonally across the table.
• The most notable diagonal relationships are between:
  • Lithium (Li) and Magnesium (Mg)
  • Beryllium (Be) and Aluminium (Al)
  • Boron (B) and Silicon (Si)

Explanation:-

• Given the options:
  • 1) B (Boron): Boron exhibits a diagonal relationship with Silicon (Si), not Beryllium (Be).
  • 2) Na (Sodium): Sodium does not exhibit a notable diagonal relationship with Beryllium (Be).
  • 3) Mg (Magnesium): Magnesium exhibits a diagonal relationship with Lithium (Li), not Beryllium (Be).
  • 4) Al (Aluminium): Aluminium exhibits a diagonal relationship with Beryllium (Be).

Diagonal relationship

Therefore, the element that exhibits a diagonal relationship with Beryllium is Aluminium (Al).

CONCEPT:

Thermal Decomposition of Nitrates

• Nitrates of alkali metals (except lithium nitrate) generally decompose on heating to give the corresponding nitrite and oxygen.
• However, lithium nitrate behaves differently and decomposes to give lithium oxide (Li₂O), nitrogen dioxide (NO₂), and oxygen (O₂).

EXPLANATION:

• For most alkali metal nitrates (e.g., NaNO₃, KNO₃, RbNO₃):

  2MNO₃ → 2MNO₂ + O₂

  • Here, M represents the alkali metal.
  • These nitrates decompose to form metal nitrites and oxygen gas.
• For lithium nitrate (LiNO₃):

  4LiNO₃ → 2Li₂O + 4NO₂ + O₂

  • Lithium nitrate decomposes to form lithium oxide (Li₂O), nitrogen dioxide (NO₂), and oxygen (O₂).
  • This is due to the small size and high charge density of the lithium ion, which makes it behave differently from other alkali metals.

Therefore, the correct answer is option 4: LiNO₃.