Do you remember learning that some elements show similar properties? How does it happen? The 10th chapter from class 11 Chemistry syllabus, s-block elements will enlighten us with various scientific reasons behind these similarities. Belonging to inorganic chemistry, s block elements is an important chapter 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.
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Understanding the s Block Elements
As per the chemistry class 11 syllabus, the s-block 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 s-electron in the valence shell of their atoms – two and one, respectively.
s Block Elements: Alkali Metals
The Alkali Metals have got their names because of their reaction with water results in alkalies (strong bases – 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.
s Block Elements: Diagonal Relationships
Diagonal Relationships is 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, properties of Lithium (Li) and Beryllium (Be) can be found to be similar.
Some Properties of Alkali Metals
To fully understand the s block elements chapter, it is important to go through the properties of alkali metal. As per NCERT chemistry class 11, the alkali metals belonging to the s 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 +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 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 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]
Some Properties of Alkaline Earth Metals
The Class 11 NCERT notes on s block elements 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+) forming 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:
Solved Examples for s Block Elements
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.
Hopefully, through this blog, you are now familiar with the important topics and points of the s block elements of the chapter 10 class 11. Reach out to our experts at Leverage Edu and they will assist you in choosing the right career path after class 12th.