SUMMARY: This chapter focuses on the properties, occurrence, and uses of the s-block elements, which include the alkali and alkaline earth metals. KEY TOPICS: Alkali metals, alkaline earth metals, electronic configuration, chemical reactivity, trends in properties, occurrence in nature, biological importance, anomalous behavior of lithium and beryllium, diagonal relationship, compounds of s-block elements.
Which of the following alkali metals has the highest melting point?
ALithium
BSodium
CPotassium
DRubidium
Check answerHide answer
Correct answer: Option 1 — Lithium
Q21 Mark
What is the electronic configuration of sodium (Na)?
A1s² 2s² 2p⁶ 3s¹
B1s² 2s² 2p⁶ 3s²
C1s² 2s² 2p⁶ 3p¹
D1s² 2s² 2p⁶ 3d¹
Check answerHide answer
Correct answer: Option 1 — 1s² 2s² 2p⁶ 3s¹
Q31 Mark
Which of the following compounds is formed when lithium reacts with water?
ALiOH
BLi2O
CLi2CO3
DLiCl
Check answerHide answer
Correct answer: Option 1 — LiOH
Q41 Mark
Beryllium differs from other alkaline earth metals in that it:
AForms a stable oxide
BIs not a good conductor of electricity
CHas a higher ionization energy
DIs more reactive with water
Check answerHide answer
Correct answer: Option 3 — Has a higher ionization energy
Q51 Mark
Which of the following elements exhibits anomalous behavior among alkali metals?
ASodium
BPotassium
CLithium
DRubidium
Check answerHide answer
Correct answer: Option 3 — Lithium
Q61 Mark
The diagonal relationship in the periodic table is observed between which two pairs of elements?
ALi and Mg
BNa and Al
CK and Ca
DRb and Sr
Check answerHide answer
Correct answer: Option 1 — Li and Mg
Q71 Mark
Which alkaline earth metal is primarily used in fireworks for its bright white flame?
ABarium
BCalcium
CMagnesium
DStrontium
Check answerHide answer
Correct answer: Option 3 — Magnesium
Q81 Mark
What is the primary reason for the high reactivity of alkali metals?
ALow electronegativity
BHigh ionization energy
CLarge atomic size
DPresence of one valence electron
Check answerHide answer
Correct answer: Option 4 — Presence of one valence electron
Q91 Mark
Which of the following statements about beryllium is true?
AIt readily reacts with water
BIt forms covalent compounds
CIt has a low melting point
DIt is highly soluble in water
Check answerHide answer
Correct answer: Option 2 — It forms covalent compounds
Q101 Mark
What is the common oxidation state of alkali metals in their compounds?
A+1
B+2
C0
D-1
Check answerHide answer
Correct answer: Option 1 — +1
Q111 Mark
Which of the following is a characteristic property of alkaline earth metals?
AThey are all gases at room temperature
BThey have a higher density than alkali metals
CThey do not react with acids
DThey are all radioactive
Check answerHide answer
Correct answer: Option 2 — They have a higher density than alkali metals
Q121 Mark
Which of the following compounds is used in the preparation of hydrogen gas?
ANaOH
BLiAlH4
CCaO
DMgCl2
Check answerHide answer
Correct answer: Option 2 — LiAlH4
Q131 Mark
The solubility of alkali metal hydroxides in water generally:
ADecreases down the group
BIncreases down the group
CRemains constant
DVaries randomly
Check answerHide answer
Correct answer: Option 2 — Increases down the group
Q141 Mark
Which of the following is NOT a property of alkali metals?
ASoftness
BHigh density
CLow melting point
DGood conductors of heat
Check answerHide answer
Correct answer: Option 2 — High density
Q151 Mark
Which alkaline earth metal is essential for human health and is found in bones?
ABarium
BCalcium
CStrontium
DMagnesium
Check answerHide answer
Correct answer: Option 2 — Calcium
Short Answer Questions10 questions
Q163 Marks
What is the electronic configuration of alkali metals and how does it influence their reactivity?
View sample solutionHide solution
Alkali metals have the electronic configuration of ns^1, where 'n' represents the principal quantum number. This single valence electron makes them highly reactive, as they readily lose this electron to achieve a stable noble gas configuration.
Q173 Marks
Explain the trend in ionization energy among alkali metals down the group. Why does it decrease?
View sample solutionHide solution
Ionization energy decreases down the group of alkali metals due to the increase in atomic size and the shielding effect. As the atomic radius increases, the outermost electron is further from the nucleus and is less tightly held, making it easier to remove.
Q183 Marks
What are the main uses of sodium and potassium in biological systems?
View sample solutionHide solution
Sodium and potassium are essential electrolytes in biological systems. Sodium helps in maintaining fluid balance and is crucial for nerve impulse transmission, while potassium is vital for muscle contraction and heart function.
Q193 Marks
Describe the anomalous behavior of lithium compared to other alkali metals. What are the reasons for this behavior?
View sample solutionHide solution
Lithium exhibits anomalous behavior due to its small size, high ionization energy, and strong polarizing power. These properties lead to differences in its reactivity and the nature of its compounds compared to other alkali metals.
Q203 Marks
What are the common oxidation states of alkaline earth metals and how do they achieve these states?
View sample solutionHide solution
Alkaline earth metals commonly exhibit a +2 oxidation state, achieved by losing their two valence electrons. This loss leads to the formation of stable cations with a noble gas electron configuration.
Q213 Marks
Explain the diagonal relationship between lithium and magnesium. What are its implications?
View sample solutionHide solution
The diagonal relationship between lithium and magnesium arises from their similar charge density and ionic radii. This results in comparable properties, such as solubility in water and the formation of covalent compounds, which differ from their respective groups.
Q223 Marks
What is the significance of beryllium's anomalous behavior among alkaline earth metals?
View sample solutionHide solution
Beryllium's anomalous behavior is significant because it forms covalent compounds and has a higher ionization energy compared to other alkaline earth metals. This is due to its small size and high charge density, leading to strong covalent bonding.
Q233 Marks
List the common compounds formed by alkali metals and their general properties. What are their uses?
View sample solutionHide solution
Common compounds formed by alkali metals include oxides, hydroxides, and halides. These compounds are typically ionic, soluble in water, and exhibit strong basic properties, making them useful in various applications such as cleaning agents and in chemical synthesis.
Q243 Marks
How does the reactivity of alkaline earth metals change down the group?
View sample solutionHide solution
The reactivity of alkaline earth metals increases down the group due to the decrease in ionization energy and increase in atomic size. As the atoms get larger, it becomes easier to lose the two outermost electrons, enhancing their reactivity.
Q253 Marks
What role do alkali metals play in the human body?
View sample solutionHide solution
Alkali metals, particularly sodium and potassium, play crucial roles in the human body by regulating fluid balance, transmitting nerve impulses, and facilitating muscle contractions, which are essential for overall physiological functions.
Long Answer Questions6 questions
Q266 Marks
Differentiate between alkali metals (Group 1) and alkaline earth metals (Group 2) in tabular form.
Q276 Marks
Compare lithium with other alkali metals (anomalous behaviour) with the help of a table.
Q286 Marks
Explain the electronic configuration of alkali metals and how it influences their chemical reactivity. Provide examples to support your explanation.
View sample solutionHide solution
Alkali metals have a single electron in their outermost shell, which is in the s-orbital. This configuration makes them highly reactive as they tend to lose this electron easily to achieve a stable noble gas configuration. For instance, lithium (Li) has the configuration 1s² 2s¹, and it readily loses its outermost electron to form Li⁺. Similarly, sodium (Na) with the configuration 1s² 2s² 2p⁶ 3s¹ loses its single 3s electron to form Na⁺. This trend in reactivity increases down the group due to the decreasing ionization energy.
Q296 Marks
Discuss the diagonal relationship between lithium and magnesium, highlighting their similarities and differences in properties and compounds.
View sample solutionHide solution
The diagonal relationship between lithium (Li) and magnesium (Mg) arises due to their similar ionic sizes and charge density. Both elements form stable oxides (Li₂O and MgO) and nitrides (Li₃N and Mg₃N₂). However, lithium is more soluble in organic solvents compared to magnesium, which prefers to form ionic compounds. Additionally, lithium salts are generally more covalent than magnesium salts due to the higher polarization power of Li⁺. This relationship is significant in understanding the behavior of these elements in various chemical reactions and their applications.
Q306 Marks
Describe the occurrence of alkali metals in nature and the methods used for their extraction.
View sample solutionHide solution
Alkali metals are highly reactive and do not occur freely in nature; they are found in various minerals and salts. For instance, sodium is primarily found in the form of halite (NaCl) and potassium in sylvite (KCl). The extraction of alkali metals typically involves the electrolysis of their molten salts. For example, sodium can be extracted by electrolyzing molten sodium chloride, where sodium metal is deposited at the cathode and chlorine gas is released at the anode. This method is essential for obtaining pure alkali metals for industrial applications.
Q316 Marks
Explain the biological importance of sodium and potassium in living organisms, including their roles in physiological processes.
View sample solutionHide solution
Sodium (Na⁺) and potassium (K⁺) are vital for various physiological processes in living organisms. Sodium is crucial for maintaining osmotic balance and is involved in nerve impulse transmission and muscle contraction. Potassium, on the other hand, plays a key role in cellular functions, including maintaining membrane potential and facilitating the transport of nutrients and waste products. The sodium-potassium pump actively transports Na⁺ out of cells and K⁺ into cells, which is essential for maintaining the electrochemical gradient necessary for nerve signal conduction and muscle function.
Assertion–Reason Questions8 questions
Q321 Mark
Assertion (A): Alkali metals are highly reactive due to their low ionization energies.
Reason (R): The reactivity of alkali metals increases down the group as ionization energy decreases.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q331 Mark
Assertion (A): Lithium exhibits anomalous behavior compared to other alkali metals.
Reason (R): Lithium has a smaller atomic radius and higher electronegativity than other alkali metals.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q341 Mark
Assertion (A): Beryllium is more reactive than magnesium.
Reason (R): Beryllium has a higher ionization energy than magnesium, making it less reactive.
Show explanationHide explanation
Correct answer: Option 4 —
A is false, but R is true.
Q351 Mark
Assertion (A): The electronic configuration of sodium is 1s² 2s² 2p⁶ 3s¹.
Reason (R): Sodium belongs to the alkali metals group which has one electron in the outermost shell.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q361 Mark
Assertion (A): Alkaline earth metals are less reactive than alkali metals.
Reason (R): Alkaline earth metals have two electrons in their outermost shell, requiring more energy to remove them.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q371 Mark
Assertion (A): The diagonal relationship exists between lithium and magnesium.
Reason (R): Both lithium and magnesium exhibit similar properties due to their comparable ionic sizes and charge densities.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q381 Mark
Assertion (A): Potassium reacts with water to form potassium hydroxide and hydrogen gas.
Reason (R): All alkali metals react with water to produce hydroxides and hydrogen gas.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q391 Mark
Assertion (A): Beryllium hydroxide is amphoteric in nature.
Reason (R): Beryllium has a high charge density which allows its hydroxide to react with both acids and bases.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Statement-Based Questions8 questions
Q401 Mark
Statement 1: Alkali metals have a single electron in their outermost shell.
Statement 2: Alkaline earth metals have two electrons in their outermost shell.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q411 Mark
Statement 1: Lithium is less reactive than sodium.
Statement 2: Beryllium is more reactive than magnesium.
Show answerHide answer
Correct answer: Option 4 —
Both statements are false.
Q421 Mark
Statement 1: The diagonal relationship exists between lithium and magnesium.
Statement 2: The diagonal relationship is due to similar ionic sizes and charge densities.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q431 Mark
Statement 1: Sodium is more soluble in water than potassium.
Statement 2: Potassium reacts vigorously with water to produce hydrogen gas.
Show answerHide answer
Correct answer: Option 2 —
Only Statement 1 is true.
Q441 Mark
Statement 1: Alkali metals are known for their high melting points.
Statement 2: Alkaline earth metals generally have higher melting points than alkali metals.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q451 Mark
Statement 1: Calcium is used in the extraction of metals from their ores.
Statement 2: Barium is commonly used in fireworks.
Show answerHide answer
Correct answer: Option 2 —
Only Statement 1 is true.
Q461 Mark
Statement 1: The electronic configuration of sodium is 1s² 2s² 2p⁶ 3s¹.
Statement 2: The electronic configuration of magnesium is 1s² 2s² 2p⁶ 3s².
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q471 Mark
Statement 1: Lithium forms a stable oxide when burned in air.
Statement 2: Sodium forms a superoxide when burned in air.
Show answerHide answer
Correct answer: Option 3 —
Only Statement 2 is true.
