Class 11 Chapter 10 S Block Elements Notes

Do you remember learning that some elements show similar properties? How does it happen? The 10th chapter from the class 11 Chemistry syllabus, s-block elements will enlighten us with various scientific reasons behind these similarities. Belonging to inorganic chemistry, s block elements notes are important to cover.  If you are exploring detailed notes for this chapter, then, go through the blog which contains simple and easy-to-learn notes for this chapter.

s Block Elements NCERT PDF

Understanding the s Block Elements 

As per the chemistry class 11 syllabus, elements have an entire chapter based on them. Group 1 and group 2 elements combined are known as s-block elements. Group 1 elements are Alkali Metals, while group 2 elements are Alkaline Earth Metals. Alkaline earth metals and alkali metals are both characterized by the presence of an s-electron in the valence shell of their atoms – two and one, respectively. 

s Block Elements Name

Do you know all the elements in s Block? Here is the list of all elements you should know:

1. Hydrogen (H)
2. Lithium (Li)
3. Helium (He)
4. Sodium (Na)
5. Beryllium (Be)
6. Potassium (K)
7. Magnesium (Mg)
8. Rubidium (Rb)
9. Calcium (Ca)
10. Cesium (Cs)
11. Strontium (Sr)
12. Francium (Fr)
13. Barium (Ba)
14. Radium (Ra)

s Block Elements: Alkali Metals

Alkali Metals have got their names because their reaction with water results in alkalies (strong bases – the opposite of acids, and capable of neutralizing them). The six elements that are in Group 1 are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr). The metals are silvery-white in appearance and are soft and low-melting, but highly volatile. Both ionic and atomic sizes increase as we go down the table.  

s Block Elements: Alkaline Earth Metals

Alkaline Earth Metals are shiny and silvery-white. The s-block elements are found in Group 2 of the atomic table. Alkaline Earth metals are Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). They are somewhat reactive in standard conditions of temperature and pressure. heir hydroxides and oxides are less basic as compared to Alkali metals.

Difference Between Alkali Metals and Alkali Earth Metals

	Properties	Alkaline earth metals	Alkali metals
1.	Electronic configuration	Two electrons are present in the valency shell. The configuration is ns2 (bivalent)	One electron is present in the valency shell. The configuration is ns1 (monovalent) more electropositive
2.	Valency	Bivalent	Monovalent
3.	Electropositive nature	Less electropositive	More electropositive
4.	Hydroxides	Weak bases, less soluble and decompose on heating.	Strong bases, highly soluble and stable towards heat.
5.	Bicarbonates	These are not known in a free state. Exist only in solution.	These are known in the solid state.
6.	Carbonates	Insoluble in water. Decompose on heating.	Soluble in water. Do not decompose on heating (LiCO3 is an exception)
7.	Action of nitrogen	Directly combine with nitrogen and form nitrides	Do not directly combine with nitrogen except with lithium
8.	Action of carbon	Directly combine with carbon and form carbides	Do not directly combine with carbon
9.	Nitrates	Decompose on heating evolving a mixture of NO2 and oxygen	Decompose on heating evolving only oxygen
10.	Solubility of salts	Sulphates, phosphates fluorides, chromates, oxalates etc are insoluble in water	Sulphates, phosphates, fluorides, chromates, oxides etc are soluble in water.
11.	Physical properties	Comparatively harder. High melting points. Diamagnetic.	Soft, low melting points paramagnetic.
12.	Hydration of compounds	The compounds are extensively hydrated. MgCl2.6H2O, CaCl2.6H2O, and BaCl2.2H2O are hydrated chlorides.	The compounds are less hydrated. NaCl, KCl, and RbCl form non–hydrated chlorides
13.	Reducing power	Weaker as ionization potential values are high and oxidation potential values are low.	Stronger as ionization potential values are low and oxidation potential values are high.

s Block Elements: Diagonal Relationships

Diagonal Relationships are one of the important concepts of class 11 s block elements. As per the diagonal relationship, the first element of group 1 and the second element of group 2 show similar properties. For Example, the properties of Lithium (Li) and Beryllium (Be) can be found to be similar.

Some Properties of Alkali Metals

To fully understand this chapter, it is important to go through the properties of alkali metals. As per NCERT chemistry class 11, the alkali metals belonging to this block exhibit the following properties-

• The metals have low melting and boiling point because of the prevalence of weak metallic bonds. They decrease as we go further down the table, with Francium being liquid at room temperature
• They are soft, malleable, and ductile. They can even be cut by a knife, and the oscillation of electrons induces a metallic lustre when freshly cut
• Atomic volume is high and increases from top to bottom
• Electropositivity is high in alkali metals due to low ionization enthalpy, and it increases further from top to bottom due to a further decrease in ionization enthalpy. For Example: Li+ > Na+ > K+ > Rb+ > Cs+
• Alkali magnets are diamagnetic in nature. They show noble gas configuration with only a +1 oxidation state
• The electrical conductivity is high of the s block elements and increases down the table. For Example: Li+ < Na+ < K+ < Rb+ < Cs+
• When exposed to light, alkali metals showcase a photoelectric effect because of low ionization enthalpy 
• Alkali metals are good reducing agents in the order: Na < K < Rb < Cs < Li
• They form oxides, hydroxides, and carbonates, very easily when exposed to moisture. Hence, they are kept in an inert liquid like kerosene oil, while lithium floats on kerosene due to low density and is wrapped in paraffin wax   
• Upon heating with oxygen, oxides, peroxides, and superoxides are formed, the stability of which increases as we go down the table. They are basic in nature with strength being: Li2O < Na2O < K2O < Cs2O
• Upon reaction with compounds with acidic hydrogen-like water, the reaction is like 2m + 2H2O → 2mOH + H2 (where m = The Alkali Metal)
• Upon reaction with hydrogen, the following sequence occurs in s block elements: 2m + H2O → 2H (where m = The Alkali Metal)
• Ionic halides results when Alkali metals are made to react with halogens, barring a few lithium halides, and the reaction is as follows:  2m + X2 → 2m+ X– (where, m = The Alkali Metal, and X = F, Cl, Br, 1]

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Some Properties of Alkaline Earth Metals

It contains another important aspect – the Alkaline Earth Metals. Their properties, reactions, and exceptions are thoroughly explained in the NCERT book, let’s learn about some of the properties of Alkaline Earth Metals-

• The presence of a higher number of bonding electrons results in higher melting and boiling points, although they decrease down the table. Magnesium remains an exception
• Strong electropositivity in alkaline earth metals is a result of large size and lower ionization enthalpy. Increase in the atomic radius of the respective metals and decrease in their ionization enthalpy 
• A +2 oxidation state is seen, which makes the dipositive ions (M2+) form strong lattices in the solid state because of high charge and small size, also known as high lattice enthalpy
• Compared to their alkali counterparts, alkaline earth metals belonging to the s-block elements are not as reactive with water. The reaction is: m + 2H2O → m(OH)2 + H2 (where, m = Mg, Ca, Sr or Ba)
• When heated with oxygen; Be, Mg, and Ca form monoxides and Sr, Ba, and Ra form peroxides.
• Except Be, all these metals displace hydrogen from acids

Electronic Configuration of s Block Elements

The electronic configuration is divided into 2 groups. We have a tabulated version of both groups:

Electronic Configuration Elements Group- 1

Element	Symbol	Electronic configuration
Lithium	Li	1s22s1
Sodium	Na	1s22s22p63s1
Potassium	K	1s22s22p63s23p64s1
Rubidium	Rb	1s22s22p63s23p63d104s24p65s1
Caesium	Cs	[Xe]6s1
Francium	Fr	[Rn]7s1

Electronic Configuration Group- 2

Elements	Symbols	Electronic configuration
Beryllium	Be	[He]2s2
Magnesium	Mg	[Ne]3s2
Calcium	Ca	[Ar]4s2
Strontium	Sr	[Kr]5s2
Barium	Ba	[Xe]6s2
Radium	Ra	[Rn]7s2

s Block Elements Properties

Solved Examples

Some of the Class 11 Chemistry NCERT Solutions with Questions:

Q. Why are alkali metals not found in nature?
They are highly reactive, and have a single electron in the valence shell, making them near impossible to be found in the elemental state in nature.

Q. Explain why sodium is less reactive than potassium.
As we move down the table in Group 1 elements, the effect of nuclear charge gets decreased as the size of the atom increases. This makes Potassium more reactive as the outer electron can be easily lost when compared to Sodium. 

s & p Block Elements PPT

S & p block elements from Sidra Javed

Summary

1. s-block elements: These are the elements in which the last electron reaches the s-orbital.
2. Alkali metals: Group 1 elements with strong alkali hydroxide.
3. Alkaline Earth Metal– Group 2 elements, as well as their oxides and hydroxides, are alkaline in nature, and their oxides are found in the Earth’s crust.
4. Diagonal relationship: The similarity in attributes of second-period elements to third-period components present diagonally on the right-hand side.
5. Monovalent sodium and potassium ions, as well as divalent magnesium and calcium ions, are abundant in biological fluids. These ions serve critical biological tasks such as ion balance maintenance and nerve impulse conduction.

FAQs

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