Important Questions for CBSE Class 11 Chemistry Chapter 10 – The s-Block Elements

Important Questions Class 11 Chemistry Chapter 10 – The s-Block Elements

Chemistry is a subject based on theories, numerical, experiments, laws, principles, observations and conclusions. As a result, the subject is quite vast, and thus experts suggest students to revise the subject again and again with suitable study material hence parents and teachers trust Class 11 Chemistry Chapter 10 s block elements important questions to the fullest.

The s-Block elements are on the periodic table’s upper left-hand side. It is one of the smallest blocks of the periodic table. It comprises two groups. The main topics covered in the Chapter 10 Class 11 Chemistry S-block elements important questions include

  • Group 1 element: alkali metals, 
  • General characteristics of the compounds of the alkali metals, 
  • Anomalous properties of Lithium, 
  • Some important compounds of sodium, 
  • Biological importance of sodium and potassium, 
  • Group 2 elements: alkaline earth metals, 
  • General characteristics of compounds of the alkaline earth metals, 
  • Anomalous behaviour of beryllium, 
  • Some important compounds of calcium,   
  • Biological importance of magnesium and calcium.

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CBSE Class 11 Chemistry Important Questions
Sr No Chapters Chapter Name
1 Chapter 1 Some Basic Concepts of Chemistry
2 Chapter 2 Structure of Atom
3 Chapter 3 Classification of Elements and Periodicity in Properties
4 Chapter 4 Chemical Bonding and Molecular Structure
5 Chapter 5 States of Matter
6 Chapter 6 Thermodynamics
7 Chapter 7 Equilibrium
8 Chapter 8 Redox Reactions
9 Chapter 9 Hydrogen
10 Chapter 10 The s-Block Elements
11 Chapter 11 The p block Elements
12 Chapter 12 Organic Chemistry – Some Basic Principles and Techniques
13 Chapter 13 Hydrocarbons
14 Chapter 14 Environmental Chemistry

S block Elements Class 11 Important Questions with Answers

Below are a few Class 11 Chemistry Chapter 10 Important Questions and their solutions:

Question 1. The alkali metals have a low melting point. Which among the following alkali metal is expected to melt when the room temperature rises to 30°C?

(i) Na

(ii) K

(iii) Rb

(iv) Cs

Answer 1. (iv) Cs

 Option (iv) is the correct answer.

Question 2. Alkali metals react with the water vigorously to form the hydroxides and dihydrogen.

Which among the following alkali metals reacts with the water least vigorously?

(i) Li

(ii) Na

(iii) K

(iv) Cs

Answer 2. (i) Li

Option (i) is the answer.

Question 3. The reducing power of the metal depends on the different factors. Suggest the factor that makes Li one of the strongest reducing agents in the aqueous solution.

(i) Sublimation enthalpy

(ii) Ionisation enthalpy

(iii) Hydration enthalpy

(iv) Electron-gain enthalpy

Answer 3. (iii) Hydration enthalpy

Option (iii) is the answer.

Question 4. The metal carbonates decompose on heating to give the metal oxide and carbon dioxide. Which among the metal carbonates is the most stable thermally?

(i) MgCO3

(ii) CaCO3

(iii) SrCO3

(iv) BaCO3

Answer 4. (iv) BaCO3

Option (iv) is the answer.

Question 5. Which among the following carbonates given is unstable in air and is kept with the CO2 atmosphere to avoid the decomposition.

(i) BeCO3

(ii) MgCO3

(iii) CaCO3

(iv) BaCO3

Answer 5. (i) BeCO3

Option (i) is the answer.

Question 6. Metals form the basic hydroxides. Which among the following metal hydroxide is the least basic?

(i) Mg(OH)2

(ii) Ca(OH)2

(iii) Sr(OH)2

(iv) Ba(OH)2

Answer 6. (i) Mg(OH)2

Option (i) is the answer

Question 7. Some among the Group 2 metal halides are covalent and soluble in the organic solvents.

From the following metal halides, the one that is soluble in the ethanol is

(i) BeCl2

(ii) MgCl2

(iii) CaCl2

(iv) SrCl2

Answer 7. (i) BeCl2

Option (i) is the answer.

Question 8. The order for the decreasing ionization enthalpy in the alkali metals is

(i) Na > Li > K > Rb

(ii) Rb < Na < K < Li

(iii) Li > Na > K > Rb

(iv) K < Li < Na < Rb

Answer 8. (iii) Li > Na > K > Rb

Option (iii) is the answer.

Question 9. The solubility for the metal halides depends on their nature, the lattice enthalpy and the hydration enthalpy of the individual ions. From the following fluorides of the alkali metals, the lowest solubility of the LiF in water is because of the

(i) Ionic nature of lithium fluoride

(ii) High lattice enthalpy

(iii) High hydration enthalpy for lithium-ion.

(iv) Low ionization enthalpy of the lithium atom

Answer 9. (ii) High lattice enthalpy

Option (ii) is the answer.

Question 10. The amphoteric hydroxides react with both the alkalies and acids. Which among the

following Group 2, metal hydroxides are soluble in the sodium hydroxide?

(i) Be(OH)2

(ii) Mg(OH)2

(iii) Ca(OH)2

(iv) Ba(OH)2

Answer 10. (i) Be(OH)2

Option (i) is the answer.

 Question 11. Match the elements correctly given in Column I with their suitable properties mentioned in Column II.

Column I

(i) Li

(ii) Na

(iii) Ca

(iv) Ba


Column II

(a)Insoluble sulphate

(b)Strongest monoacidic base

(c) Most negative E value of the alkali metals.

(d)Insoluble oxalate

(e) 6s2

 outer electronic configuration

Answer 11.

(i) is c

(ii) is b

(iii) is d

(iv) is a,e

Question 12. Match the compounds correctly given in Column I with their right uses mentioned in Column II.

Column I

(i) CaCO3

(ii) Ca(OH)2

(iii) CaO

(iv) CaSO4

Column II

(a) Dentistry, ornamental work

(b) Manufacturing of sodium carbonate from caustic soda

(c) Manufacturing of the high-quality paper

(d) Used in the whitewashing

Answer 12.

(i) is c

(ii) is d

(iii) is b

(iv) is a

Question 13. Match the elements correctly given in Column I with the appropriate colours they impart for the flame has given in Column II.

Column I

(i) Cs

(ii) Na

(iii) K

(iv) Ca

(v) Sr

(vi) Ba

Column II

(a) Apple green

((b) Violet

(c) Brick red

(d) Yellow

(e) Crimson red

(f) Blue

Answer 13.

(i) is f

(ii) is d

(iii) is b

(iv) is c

(v) is e

(vi) is a

Question 14. For the following questions, a statement of the Assertion (A) is followed by the statement of the Reason (R). Pick the correct option out of the alternatives given below each question.

(I). Assertion (A): The carbonate of the Lithium decomposes easily on heating to form the lithium oxide and CO2.

Reason (R): Lithium being very small in size polarises large carbonate ions leading to the formation of the more stable Li2O and CO2.

(i) Both of them, A and R, are correct, and R is the correct explanation for A.

(ii) Both of them, A and R, are correct, but R is not the correct explanation for A.

(iii) Both of them A and R are not correct

(iv) A is not right, but R is correct.

Answer (I). Option (i) is correct.

(II). Assertion (A): Beryllium carbonate is kept in the atmosphere of the carbon dioxide.

Reason (R): Beryllium carbonate is unstable as well as decomposes to give beryllium oxide and the carbon dioxide.

(i) Both of them, A and R, are correct, and R is the correct explanation for A.

(ii) Both of them, A and R, are correct, but R is not the correct explanation for A.

(iii) Both of them, A and R, are not correct.

(iv) A is not correct, but R is right.

Answer (II). Option (i) is correct.

 Question 15. How do you account for the strong reducing power for the Lithium in the aqueous solution?

Answer 15. Lithium has the highest negative EӨ value, that is –3.04V. Lithium has the small atomic size and the highest ionisation enthalpy, but it is compensated by the high hydration enthalpy. As a result, the reducing power of the Lithium is highest in the aqueous solution.

Question 16. Complete the following reactions given below:

(i) O2-2 + H2O →

(ii) O-2 + H2O →

Answer 16. (i) O2-2 + 2H2O → H2O2 + 2OH-

(ii) 2O2 + 2H2O → H2O2+ O2 + 2OH

Question 17. Discuss the trend for the following:

(i) Thermal stability of the carbonates of the Group 2 elements.

(ii) The solubility and the nature of the oxides of the Group 2 elements.

Answer 17. (i) The thermal stability of the carbonates increases for the increase in the cationic size. The more stable the oxide of the alkaline earth metal, the less stable the carbonate for the same. So, BeCO3 is highly unstable, and the BeO is stable.

(ii) Alkali metals from the oxides with the oxygen and give the metal oxides. The oxides will be a basic exception to BeO as the BeO is amphoteric. They also react with the water to form the sparingly soluble hydroxides when the size of the cations increases, BeO and MgO have the highest lattice energy as well as they are insoluble in the water.

Question 18. Why are the BeSO4 and MgSO4 readily soluble in the water, whereas the CaSO4, SrSO4 and BaSO4 are insoluble?

Answer 18. BeSO4 and MgSO4 are readily soluble in the water, but CaSO4, SrSO4, and BaSO4 are insoluble. This is due to the greater hydration enthalpies of the Be2+ and Mg2+ ions. They overcome the lattice enthalpy factor, and thus, their sulphate is soluble in the water.

Question 19. All compounds of the alkali metals are easily soluble in the water, whereas the lithium compounds are more soluble in the organic solvents. Explain.

Answer 19. The alkali metal compounds form the ionic compounds because of their large ionic size and low ionization enthalpy, whereas Lithium forms the compounds of the covalent nature as their small ionic size, the high ionization enthalpy, and the high electronegativity.

Question 20. For the Solvay process, can we get the sodium carbonate directly treated with the solution containing the (NH4) 2CO3 with the sodium chloride? Explain.

Answer 20. For the Solvay process, the carbon dioxide is passed through the concentrated solution of the sodium chloride saturated with the ammonia, which forms ammonium carbonate, followed by the ammonium hydrogen carbonate. Ammonium hydrogen carbonate crystals separate as they are heated to form the sodium carbonate. The NH3 is recovered from the solution that contains the NH4Cl and then is heated when treated with Ca(OH)2. The reaction of the (NH4)2CO3 with the NaCl gives two products, Na2CO3 and NH4Cl, that are both soluble in the water that does not shift the equilibrium to the right.

Question 21. Write Lewis structure of the O-2 ion. Also, find out the oxidation state for each oxygen atom? What is the average oxidation state of the oxygen for this ion?

Answer 21. 

Source: Internet

Oxygen atoms with zero charges have six electrons. Thus the oxidation state is 0. If the oxygen atom has a negative charge, it has the seven electrons. Thus, the oxidation state is -1. The average oxidation state is 0 + (-1)/2 = -1/2.

 Question 22. What is the structure for the BeCl2 molecule in the gaseous and the solid state?

Answer 22. The gaseous/vapour state is different from the solid state. The structure of the BeCl2 in the solid-state is the polymeric chain structure. BeCl2 tends to form the chloro-bridged dimer at the temperatures below 1200K and dissociates into the linear monomer at the high temperatures of the order of 1200 K.

 Question 23. Beryllium and magnesium do not give colour for the flame, but the other alkaline earth metals do so. Why?

Answer 23. The valence electrons get excited to the higher energy level if the alkaline earth metal is heated.

It radiates energy that belongs to the visible region. If this excited electron comes back to the energy level that is low, the colour is seen. The electrons are firmly bound to the beryllium and magnesium. The energy needed to excite the electrons is very high. If the electron reverts back to the original position, the energy released does not fall in the visible region. So, no colour is observed in the flame.

Question 24. Potassium carbonate could be prepared by the Solvay process. Explain why?

Answer 24. The Solvay process is not applicable for the preparation of the potassium carbonate as the potassium carbonate is soluble in the water, and it doesn’t precipitate out as the sodium bicarbonate.

Question 25. Draw the structure for the (i) BeCl2 (vapour) (ii) BeCl2 (solid).

Answer 25. (i) BeCl2 has the linear structure and exists as the monomer in the vapour state.

(ii) For the solid phase, BeCl2 is the polymer.

Question 26. Describe the importance for the following : (i) limestone, (ii) cement, and (iii) plaster of Paris.

Answer 26. Uses of the cement:

  • Construction of the bridge
  • Plastering
  • An essential ingredient in the concrete

Uses of the Plaster of Paris:

  • Used to make the casts and the moulds
  • Used to make the surgical bandages

Uses of the limestone:

  • Preparation of the cement and the lime
  • As a flux in the iron ore smelting

Question 27. Why are the lithium salts commonly hydrated, whereas the other alkali ions are usually anhydrous?

Answer 27. As Lithium has the smallest size for all the alkali metals, it can be easily polarised to water molecules. Therefore, the smaller the size of the ion, the greater is the ability to polarise the water molecules.

Therefore, the trihydrated Lithium Chloride and the other Lithium salts could be easily polarised. Because of this, the other alkali metal ions could only form the anhydrous salts.

 Question 28. What happens if:

(i) Sodium metal is immersed in the water?

(ii) Sodium metal is heated in the free supply of the air?

(iii) Sodium peroxide gets dissolved in the water?

Answer 28. (i) Sodium reacts to form the NaOH and H2 gas if it is dropped in the water. The reaction occurs as given below:

2Na(s) + 2H2O(l) 

2NaOH(aq) + H2(g)

(ii) Sodium peroxide is formed if sodium reacts with oxygen during heating it in the presence of air. The reaction proceeds as given below:

2Na(s)  + O2(s)  


(iii) NaOH and water are formed as the result of the hydrolysis of the Sodium peroxide if it is dissolved in the water.

Na2O2(s) + 2H2O(l) 

2NaOH(aq) + H2O2(aq)

Question 29. How will you explain the following observations?

(i) BeO is almost insoluble, whereas the BeSO4 is soluble in the water.

(ii) BaO is soluble, whereas BaSO4 is insoluble in the water.

(iii) LiI is more soluble than KI in the ethanol.

Answer 29.

(i) The sizes of the Be2+ and O2- are small and are highly compatible with each other. As a result, the high amount of the lattice energy is released during the formation. The hydration energy if it is made to dissolve in the water is not enough for overcoming the lattice energy. So, BeO is almost insoluble in the water.

The size of the SO42- is large compared to the Be2+, and there is lesser compatibility and lattice energy that can be easily overcome by the hydration energy. Therefore, BeSO4 is easily soluble in the water.

(ii) The sizes of the Ba2+ and SO42- are large and are highly compatible with each other. As a result, the high amount of the lattice energy is released during their formation. The hydration energy if it is made to dissolve in the water is not enough for overcoming the lattice energy. So, BaSO4 is insoluble in the water.

The size of the O2- is small compared to the Ba2+, and there is lesser compatibility and lattice energy that can be easily overcome by the hydration energy. So, BaO is easily soluble in the water.

(iii) The lithium-ion has a smaller size, and as a result, it has the higher polarising capability. This enables it to polarise the electron cloud around the iodide ion, therefore, resulting in the greater covalent character in the LiI than KI. So, LiI is easily soluble in the ethanol.

Question 30. What are the common physical and chemical characteristics of the alkali metals?

Answer 30. Physical properties of the alkali metals:

(1) The alkali metal is soft. Hence, we can cut them easily. We can cut the sodium metal even when using the knife.

(2) Generally, the alkali metal is lightly coloured as well, as mostly they are seen as silvery white.

(3) Its atomic size is larger. Therefore, their density is low. The density of the alkali metal increases as we move down in the group from the Li to Cs, except for the K, which has lower density than the sodium.

(4)  Alkali metal has weak metallic bonding. Thus, they have low boiling and melting points.

(5) The salts present in the alkali metals expose colour to the flames as the heat of the flame excites the electrons, which are located on the outer orbital, to the higher energy level. For the excited state, electrons get reversed back to the ground level, and thus the emission of excess energy in the form of the radiation falls in the visible region.

(6) The metals like K and Cs lose electrons if they get irradiated with the light and also display the photoelectric effect.

Chemical properties of the alkali metals:

(1) Alkali metal reacts with the water and forms the oxides and hydroxides. Thus, the reaction will be more spontaneous when moving down the group.

(2) Alkali metal reacts with water as well as forms the dihydrogen and hydroxides.

General reaction:

2M + 2H20 

2M+ + 2OH– + H2   

(3) Dihydrogen reacts with the alkali metals and forms the metal hydrides. The hydrides formed have the higher melting points, and they are solids that are ionic.

2M + H2  

2M+ H–      

(4) Alkali metals directly react with the halogens and form the ionic halides except Li.

2M + CL2 

2MCI           (M = Li ,K, Rb, Cs)

It has the ability to easily distort the cloud, having the electrons that are around the –ve halide ion as the lithium-ion is smaller in size. So, the Lithium halide is naturally covalent.

(5) The alkali metals have strong reducing agents. This increases as we go down the group exception lithium. Due to the high hydration energy, it results in the strong reducing agent for all the alkali metals.

(6) For the blue-coloured solution(deep blue) that is naturally conducting, it gets dissolved in the liquid ammonia.

M +(x + y) NH3   

[ M ( NH3 )x ]+  +  [ e ( NH3)y ]–

 Question 31. Discuss the general features and trends in the properties of the alkaline earth metals

Answer 31. General features:

(i)  (Noble gas) ns2  is the electronic configuration of the alkaline earth metal.

(ii) To attain the nearest inert gas configuration, these metals lose two of the electrons. So its oxidation state is +2.

(iii)  The ionic radii and atomic radii are smaller in comparison with the alkali metals. When they moved down in the group, there was an increase in the trend of the ionic radii and atomic radii due as a result of the decrease in the effective nuclear charge.

(iv) The ionisation enthalpy is low as the alkaline earth metals are larger in size. The first ionisation enthalpy is higher in comparison with the metals of group 1.

(v) They appear as lustrous and silvery-white. They are soft like the alkali metals.

(vi) Factors that lead for the alkaline earth metals to have a high boiling point and melting points:

(*)  Atoms of alkali metals are larger than in comparison with the alkaline earth metals.

(*)  The strong metallic bonds are formed with the two valence electrons.

(vii) Ca- brick red; Sr- crimson red; Ba-apple green gives colours of the flames.

The electrons are bound strongly in the elements Be and Mg. Therefore, they do not give any colours for the flame.

The alkali metals are more reactive than the alkaline earth metals.

Chemical properties:

(i)  Reaction with the air and water:  Due to the formation of the oxide layer on the surface, beryllium and magnesium are most inert to the water and air.

(a)  BeO and Be3 N2 are formed if powdered Be is burnt in the air.

(b) In the formation of MgO and Mg3 N2, Mg is burnt when exposed to the air with dazzling sparkle as Mg is more electropositive.

(c) The formation of their respective nitrides and oxides is by the instant reaction of Sr, Ca, and Ba with air.

(d) Ca, Sr, and  Ba could react vigorously even with the water, which is cold.

(ii)  When they react with the halogens, halides are formed at high temperature.

M +X2   

MX2 (X = F,CL,Br,I)  

(iii)  Exception Be, all the alkaline earth metals react with the hydrogen to form hydrides.

(iv)  The alkaline earth metals instantly react with the acids to form salts along with the liberation of hydrogen gas.

M +2HCl

MCl2  + H2(X) 

(e) Reducing Nature: The alkaline earth metals are the strong reducing agents as the alkali metals, but the reducing power is less if compared to the alkali metals. In general, the reducing character increases from the top to the bottom.

(f) Solutions in the liquid ammonia: The alkaline earth metals dissolve in the liquid ammonia to give deep blue-black solutions like the alkali metals.

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Q.1 Read the passage given below and answer the following questions:

Alkali and alkaline earth metals along with hydrogen and helium constitute s- block elements. They have low ionization enthalpies. They have highly negative electrode potentials and hence are strong reducing agents. Their solution in liquid ammonia are conducting and also act as strong reducing agents. Their oxides are basic and their basic strength increases down the group. The solubility of carbonates and sulphates of alkali and alkaline earth metals show opposite trends. The carbonates of alkaline earth metals and lithium carbonate decompose on heating while the carbonates of other alkali metals do not decompose on heating. The bicarbonates of both alkali and alkaline earth metals on heating gives carbonates. Salts of alkali metals and alkaline earth metals conduct electricity in aqueous medium. Ions of metals get hydrated and are responsible for their electrical conductance due to their movement.

In the questions given below, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Assertion: Li2CO3 is thermally unstable while Na2CO3 is thermally stable
Reason: Both the carbonates are salts of large cations and large anions.

The alkali metals are strong reducing agents.
Reason : They have only one electron to lose from their valence shells.

Calcium oxide is reduced by carbon.
Reason: Calcium reacts with carbon to form its carbide.

Li has smaller ionic radius than Na in aqueous solution.
Reason : Li ion gets more hydrated than Na in aqueous solution.


Among the alkali metals, caesium salts exhibit maximum electrical conductance in aqueous solution.
Reason : The radius of hydrated caesium ion is highest among alkali metals.



i) c
Explanation: Li2CO3 is thermally unstable and decomposes on heating to form Li2O and CO2 but Na2CO3 is thermally stable. Li2CO3 is thermally unstable because it a salt of small cation and big anion while Na2CO3 is stable as bigger cation is stabilised by bigger anion.

ii) a
Explanation: The alkali metals are strong reducing agents because they can easily lose one electron to obtain noble gas configuration.

iii) d
Explanation: Calcium oxides is not reduced by carbon as it forms carbide.


iv) b
Explanation: Li gas larger ionic radius than Na in aqueous solution as it gets more hydrated than sodium due to its small size.


iv) c
Explanation: The radius of hydrated caesium ion is smallest among alkali metals. Lithium has highest radius in aqueous medium.
Caesium salts exhibit maximum electrical conductance in aqueous solution due to their minimum hydrated radius among alkali metals. Smaller the ion in aqueous medium, higher will be the conductivity.

Q.2 Give reasons for the following:
(i) The first ionisation enthalpy of Be is higher than that of B.
(ii) Alkali metals do not form dipositive ions.



(i) Electronic configuration of:
Be: 1s2, 2s2
B: 1s2, 2s2, 2p1
In general, the ionisation enthalpy increases on moving from left to right across a period due to increase in nuclear charge. Although the nuclear charge of boron is more than that of beryllium, yet the ionisation enthalpy of boron is lower than that of beryllium because of the stable electronic configuration of beryllium.

(ii) The general electronic configuration for alkali metals is ns1 (where n represents valence shell). By losing one valence electron, they acquire stable configuration of the nearest noble gas. Thus, they no longer exhibit the tendency to lose another electron to form a dipositive ion.

Q.3 Read the passage given below and answer the questions that follow:
The Group 2 elements comprise of Beryllium, magnesium, calcium, strontium, barium and radium. They exhibit dipositive oxidation states (M2+). They form compounds which are predominantly ionic but less ionic than the compounds of alkali metals due to increased nuclear charge and smaller size. The oxides and other compounds of beryllium and magnesium are more covalent among alkaline earth metals. The alkaline earth metals form a variety of compounds like oxides, hydroxides, carbonates, sulphates, nitrates and halides.
(a) Why does beryllium, like aluminium, show resistance towards the action of acids?
(b) Compare the thermal stability of MgCO3 and SrCO3.
(c) Give reasons for the solubility of BeSO4 and MgSO4 in water.
(d) Using chemical equations, show the action of beryllium hydroxide with acids and bases.


Why are the halides formed by beryllium covalent in nature? Draw the structure of beryllium chloride in solid state.



(a) Like aluminium, beryllium resists the action of acids because of the formation of beryllium oxide film on the surface of the metal.
(b) The thermal stability of MgCO3 is lower than that of SrCO3. The stability of the carbonates of alkaline earth metals increases down the group due to an increase in the cationic size from magnesium to strontium.
(c) BeSO4 and MgSO4 are highly soluble in water due to the higher hydration enthalpies of the Be2+ and Mg2+ ions owing to their small size which overcomes the magnitude of lattice enthalpy.
(d) The action of beryllium hydroxide with acids and bases can be represented as



(d) Due to the small size of Be2+ its charge density is very high. Following Fajan’s Rule, a cation with small size can distort the electron cloud of an anion effectively and results in the formation of a covalent bond. Therefore, the halides of beryllium are covalent in nature.

In the solid state, beryllium chloride forms a chain-like structure which can be represented as

Q.4 Lithium resembles a lot with




Magnesium is diagonally placed to lithium in the periodic table.

Q.5 The compounds formed by s- block elements are

A. always ionic.

B. always covalent.

C. predominantly ionic.

D. predominantly covalent.



As s- block elements have generally low ionization energies, their compounds are predominantly ionic with the exception of those of Li and Be.

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