S-Block Elements - Notes, Overview, Formula, Books, FAQs

The s-block elements are those elements in which the outermost electrons enter into the s-orbital. The elements of s-block are divided into two categories i.e., alkali metals or group 1 elements and alkaline earth metals or group 2 elements. Their oxides and hydroxides are alkaline in nature. The general electronic configuration of these elements is ns¹ and ns² respectively.

In this article, we cover the concept of the S-block elements. which is a very important chapter from the board exam point of view and also for the JEE Mains Exam, NEET Exam, and many other entrance exams like SRMJEE, BITSAT, WBJEE, BCECE, and more

These elements have a large number of applications in our daily life such as washing Soda, which is also known as sodium carbonate. It is used for various purposes such as water softening, the manufacture of glass, paper, paints, etc.

Limestone is also one of the important compounds of the s-block element. It is used to neutralize the acidic soils. It has various other applications as well such as, for making cement, in glassmaking industry and in construction works, etc.

There are also various other applications of s-block elements. In this article, you will get all the important information regarding this chapter like important topics, how to prepare for this chapter, and important books for preparation.

Notes for S-block Elements

Important Topics

• Group 1 element- Alkali Metal
• Physical Properties
• Chemical Properties
• 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
• Physical Properties
• Chemical Properties
• General characteristics of the compounds of the Alkaline Earth Metals
• Anomalous Behaviour of Beryllium
• Some important compounds of Calcium
• Biological importance of Magnesium and Calcium

Overview of the Chapter - s-block Elements

The s-block elements are those in which the outermost electrons exist in the s-orbital. Alkali and alkaline earth metals are respectively the members of group 1 and group 2 elements. In this chapter, there are various important properties that you need to learn such as electronic configuration, ionization enthalpy, hydration enthalpy, chemical properties, etc.

Group 1 elements: Alkali metals

(i) Electronic configuration: The alkali metals or group 1 elements have the valence shell electronic configuration of ns¹. The table given below describes the electronic configuration of the alkali metals.

(ii) Atomic and ionic radii: Alkali metal atoms have the largest sizes in their respective periods. This atomic size decreases as we move along the period and increases as we move down the group.

(iii) Ionization Enthalpy: The ionization enthalpy of the alkali metal atoms is low as compared to other atoms in their respective periods. This is because of the larger size of these atoms. As we move down the group, the ionization enthalpy further decreases because of the larger size of the atoms.

(iv) Chemical Properties

• Reactivity towards air: Alkali metals react too fast with oxygen and form oxides. Lithium being the smallest element forms monoxide, sodium forms peroxide, and other large metals form superoxides.
  $\begin{aligned} & 4 \mathrm{Li}+\mathrm{O}_2 \rightarrow 2 \mathrm{Li}_2 \mathrm{O} \\ & 2 \mathrm{Na}+\mathrm{O}_2 \rightarrow \mathrm{Na}_2 \mathrm{O}_2 \\ & \mathrm{~K}+\mathrm{O}_2 \rightarrow \mathrm{KO}_2\end{aligned}$ All these metals in their oxides have the oxidation number equal to +1.
• Reactivity towards water: Alkali metals react with water to form hydroxides and dihydrogen.$2 \mathrm{Na}+2 \mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{NaOH}+\mathrm{H}_2$
• Reactivity towards dihydrogen: Alkali metals react with dihydrogen and form hydrides.$2 \mathrm{Na}+\mathrm{H}_2 \rightarrow 2 \mathrm{NaH}$
• Reactivity towards halogens: Alkali metals react too fast with halogen elements to form alkali halides.$2 \mathrm{Na}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{NaCl}$
• Alkali metals with ammonia: These metals dissolve in liquid ammonia giving the deep blue solution.$M+(x+y) NH_3 \rightarrow\left[M\left(NH_3\right)_x\right]^{+}+\left[e\left(NH_3\right)_y\right]^{-}$

Anomalous Properties of Lithium

The deviation of the behavior of lithium from its respective elements is because of two factors:
(i) The exceptionally small size of the atom
(ii) High polarising power

Because of these above two factors, lithium has some points of differences between other alkali metals and some similarities with magnesium.

(i) Differences between Lithium and other alkali metals

• Lithium is harder and its melting point and boiling point are also higher than other alkali metals.
• Lithium is less reactive than other alkali metals.
• Lithium does not form solid hydrogen carbonate, unlike other alkali metals.
• Lithium does not form ethynide on reaction with ethyne, unlike other alkali metals.
• Lithium nitrate on heating gives lithium oxide but other alkali metal nitrates produce metal nitrite.
• Fluorides and oxides of lithium are less soluble in water than those of other alkali metals.

(ii) Similarities between Lithium and Magnesium

The similarity between lithium and magnesium is also known as the diagonal relationship with magnesium. This similarity between lithium and magnesium arises because of their similar sizes.

• Lithium and Magnesium, both are harder and lighter than their respective group elements.
• Their oxides and hydroxides are less soluble.
• Both oxides of lithium and magnesium do not combine with excess oxygen.
• The chlorides of both lithium and magnesium are soluble in ethanol.
• Both form nitride in reaction to nitrogen, known as lithium nitride and magnesium nitride.

Some Important Compounds of Sodium

There are some important compounds of sodium from an industrial basis. Their production and uses are discussed below.
(i) Sodium Carbonate
(ii) Sodium Chloride
(iii) Sodium Hydroxide
(iv) Sodium hydrogen carbonate

Group 2 elements: Alkaline Earth Metals

(i) Electronic configuration: The alkaline earth metals or group 2 elements have the valence shell electronic configuration of ns². The table given below describes the electronic configuration of the alkali metals.

(ii) Atomic and ionic radii: Alkaline earth metal atoms have larger sizes than other metal atoms in their respective periods but are smaller than the alkali metals. This atomic size decreases as we move along the period and increases as we move down the group.

(iii) Ionization Enthalpy: The ionization enthalpy of the alkali metal atoms is low as compared to other atoms in their respective periods but higher than the alkali metal atoms. As we move down the group, the ionization enthalpy further decreases because of the larger size of the atoms.

(iv) Chemical Properties

• Reactivity towards air and water: Beryllium and magnesium are usually inert as they are covered with an oxide film on their surface. But the powdered beryllium burns in air and forms beryllium oxide. Other heavier elements of this group readily react with air and form oxides.
• Reactivity towards halogens: All alkaline earth metals combine with halogen to form halides.$\mathrm{Mg}+\mathrm{Cl}_2 \rightarrow \mathrm{MgCl}_2$
• Reactivity towards hydrogen: Except beryllium, all other alkaline earth metals combine with hydrogen to form their hydrides.
• Reactivity towards acids: The alkaline earth metals react with acids and liberate hydrogen.$\mathrm{Mg}+2 \mathrm{HCl} \rightarrow \mathrm{MgCl}_2+\mathrm{H}_2$
• Alkaline earth metals with ammonia: These metals dissolve in liquid ammonia and give a blue-black solution.$M+(x+y) NH_3 \rightarrow\left[M\left(N H_3\right)_x\right]^{2+}+2\left[e\left(N_3\right)_y\right]^{-}$

Diagonal Relationship between Beryllium and Aluminium:

• Aluminum and Beryllium both have oxide film on their surface thus are not easily attacked by acids.

• Both aluminum hydroxide and beryllium hydroxide react with alkali to form beryllate and aluminate ions

• Both aluminum and beryllium react with chlorine and form polymeric chlorides. These chlorides are soluble in organic solvents.
• Aluminum and Beryllium ions, both have a strong tendency to form complexes.

Some Important Compounds of Calcium

(i) Calcium Oxide or Quick Lime(CaO)
(ii) Calcium Hydroxide (Slaked lime), Ca(OH)2
(iii) Calcium Carbonate, CaCO₃
(iv) Calcium Sulphate (Plaster of Paris), CaSO₄·H₂O

How to prepare for p-Block elements?

• This chapter is a part of inorganic chemistry. It is completely theory-based and very easy to learn, no need to memorize any formula.

• Before reading this chapter, first, you must have the basic knowledge of the chapter - periodic classification of elements.

• You must also learn why there are some elements like Boron and Carbon show anomalous behavior with respect to other elements in their group.

• Rest this complete chapter is very simple, just be regular and be consistent in your numerical practice.

Uses of S-block elements

S-block elements have a large number of uses in our daily lives s-block elements form various compounds or salts that are helpful in our daily lives.

• They are used for the manufacture of various paper, soap, artificial silk, and glass.
• s-block elements have use in petroleum refining and for mercerizing cotton
• Alkaline earth metals are used in the production of medicines such as antacids and medicines used in cancer treatments.

Prescribed Books

First, you must finish the class XI textbook and solve each and every example and unsolved question given in it. Then for advanced level preparation like JEE and NEET, you must follow O.P. Tandon or Solomons and Fryhle. You must definitely solve the previous year's papers.

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