The s-Block Elements

s-block Elements

Q: How many elements are there in s-block?

The s-block of the periodic table contains a total of 14 elements. These include the alkali metals (Group 1) and the alkaline earth metals (Group 2), which collectively occupy the s orbital in their outermost electron shell.

Q: How do the chemical properties of alkali metals and alkaline earth metals differ?

While both groups are highly reactive, alkali metals are more reactive than alkaline earth metals. Alkali metals have one valence electron to lose in forming an ion, whereas alkaline earth metals have two. The second ionization energy of alkaline earth metals (the energy required to remove a second electron) adds an extra step and more energy compared to alkali metals, making them slightly less reactive.

Q: What are some important applications of s-block elements?

Alkali Metals (e.g., Sodium and Potassium): Used in various applications such as street lighting (sodium vapor lamps), fertilizers (potassium compounds), and in some types of glass manufacturing. Alkaline Earth Metals (e.g., Magnesium and Calcium): Magnesium is used in lightweight alloys and fireworks, while calcium is crucial in the production of cement and when extracted from limestone, is used in the steelmaking process.

The "s-block" in the periodic table refers to the two groups of elements located in the leftmost part of the periodic table: Group 1 and Group 2. These elements are characterized by their outermost electrons occupying the s orbital of their respective electron shells.

1.0What are s-block Elements?

The s-block elements in the Periodic Table are those where the last electron enters the outermost s-orbital. Two groups, 1 and 2, belong to the s-block. Here is s-block element’s position in periodic table-

Group 1 includes- Lithium, Sodium, Potassium, Rubidium, Caesium, and Francium, collectively known as the alkali metals. They are named so because they form strongly alkaline hydroxides when reacting with water.

Group 2 comprises- Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium. Except for beryllium, they are known as the alkaline earth metals, as their oxides and hydroxides are alkaline and are commonly found in the earth’s crust.

Alkali metals and alkaline earth metals are both groups of elements found in the s-block of the periodic table, but they have distinct differences in their properties and reactivities.

2.0Electronic Configuration of s-block Elements

Group- 1 Electronic Configuration-

Element	Symbol	Electronic configuration
Lithium	Li	1s²s¹
Sodium	Na	1s²2s²2p⁶3s¹
Potassium	K	1s²2s²2p⁶3s²3p⁶4s¹
Rubidium	Rb	1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s¹
Caesium	Cs	1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶6s¹ Or [Xe] 6s¹
Francium	Fr	[Rn]7s¹

Group-2 Electronic Configuration-

Element	Symbol	Electronic configuration
Beryllium	Be	1s²2s²
Magnesium	Mg	1s²2s²2p⁶3s²
Calcium	Ca	1s²2s²2p⁶3s²3p⁶4s²
Strontium	Sr	1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s²
Barium	Ba	1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶6s² or [Xe]6s²
Radium	Ra	[Rn]7s²

3.0Properties of s block

Here we will discuss some unique and important properties of s-block elements.

Physical Properties of s-block Elements

Alkali Metals	Alkali Earth Metals
One electron in outermost shell & General formula- ns¹	Two electrons in outermost shell & General formula- ns²
Francium is a radioactive element.	Radium is a radioactive element.
All are silvery white	All are silvery white.
Light soft, malleable and ductile metalswith metallic lustre.	These metals are harder than alkali metals.

Atomic size
Alkali Metals	Alkali Earth Metals
Largest in their respective period (except noble gas element)	Smaller than IA group elements, since extra charge on nucleus attracts the electron cloud.
Size increases from Li to Cs due to addition of an extra shell. Li < Na < K < Rb < Cs	Size increases gradually from Be to Ba Be < Mg < Ca < Sr < Ba

Note- In s-block elements Beryllium (Be) has the smallest size, while Caesium (Cs) has the largest size.

Melting and Boiling Point
Alkali Metals	Alkali Earth Metals
Weak interatomic bonds are due to their large atomic radii and presence of only one valence electron hence melting point and boiling point are low.	Metallic bond is stronger than IA group due to smaller atomic size and two electrons in valence shell hence melting point and boiling point are higher.
Size increases from Li to Cs due to addition of an extra shell. Li < Na < K < Rb < Cs	Decreasing order of melting point Be > Ca > Sr > Ba > Mg Boiling point Be > Ba > Ca > Sr > Mg

Oxidation State

Alkali Metals

Alkali Earth Metals

The alkali metals shows only + 1 oxidation state.

(difference between IE₁ and IE₂ > 16eV)

Alkaline earth metal shows +2. Oxidation state.

(difference between IE₁ and IE₂ < 11eV)

Size increases from Li to Cs due to addition of an extra shell.

Li < Na < K < Rb < Cs

Size increases gradually from Be to Ba

Be < Mg < Ca < Sr < Ba

Note- In s-block elements Be has smallest size, while Cs has largest size.

Flame test- The flame test is a method used to identify the presence of certain metal ions in a compound by observing the color of the flame when the compound is heated. Different metals produce characteristic flame colors due to electronic transitions, allowing for qualitative analysis.

Alkali Metals

Alkali Earth Metals

Alkali metals and their salts gives characteristic colour to bunsen flame. The flame energy causes an excitation of the outer most electron which on dropping back to ground state emits absorbed energy as a visible light.

Due to small size of Be & Mg outer most n electrons are tightly bounded. So not excited to higher level, hence they do not give flame test.

Li - Crimson red;

Na - Golden yellow

K-Violet; Rb - Red violet; Cs-Blue

Ca-Brick red; Sr-Crimson red;

Ba- apple green

Chemical Properties of s-block Elements

Reactivity-

Alkali Metals

Alkali Earth Metals

These elements are very reactive, so they are not found in free state in nature.

Reactivity ∝ 1ionisation potential

Less reactive than alkali metals.

Order of reactivity –

Li < Na < K < Rb < Cs

Order of reactivitity –

Be < Mg < Ca < Sr < Ba

Reactions with air-

Alkali Metals	Alkali Earth Metals
Alkali metals gets tarnish in air due to the formation of oxide at their surface hence they are kept in kerosene or paraffin wax.	Except Be, these metals easily tarnished in air. Beryllium in powdered form, burns brilliantly on ignition in air.
These elements reacts with moist air to form carbonates 4Na + O₂ ⇾ 2Na₂O Na₂O + H₂O ⇾ 2NaOH (moist) 2NaOH + CO₂⇾ Na₂CO₃ + H₂O (in air)	In moist air, except Be all the elements converts into carbonates.
In dry air only Li gives nitride and oxide both while other elements gives only oxides.	In dry air all elements of II A give nitride and oxide both.

4.0Important Compounds of s-block Elements

NaCl (Sodium Chloride):

Properties: It is a white crystalline solid with a high melting point. It is highly soluble in water and forms a salty solution.
Uses: Commonly known as table salt, it is used as a seasoning and preservative in food. It is also used in the production of chemicals, in the food processing industry, and in water softening.

NaOH (Sodium Hydroxide):

Properties: It is a white solid at room temperature, highly soluble in water, and forms a strongly alkaline solution.
Uses: Sodium hydroxide is widely used in the manufacture of pulp and paper, textiles, soaps, detergents, and various types of cleaners. It is also used in the production of biodiesel, as a pH regulator in water treatment, and in many chemical processes.

NaHCO₃ (Sodium Bicarbonate):

Properties: It is a white crystalline solid with a slightly alkaline taste. It is moderately soluble in water.
Uses: Sodium bicarbonate, commonly known as baking soda, is used as a leavening agent in baking. It is also used as an antacid to relieve heartburn and indigestion. Additionally, it finds applications in cleaning and deodorizing.

Na₂CO₃ (Sodium Carbonate):

Properties: It is a white, odorless solid, soluble in water. It is alkaline in nature.
Uses: Sodium carbonate, also known as soda ash or washing soda, is used in glassmaking, detergent production, and in the manufacturing of various chemicals. It is also used in water treatment processes and as a pH regulator in swimming pools.

CaO (Calcium Oxide):

Properties: It is a white, caustic solid with a high melting point. It reacts vigorously with water to form calcium hydroxide.
Uses: Calcium oxide, also known as quicklime, is used in various industrial processes such as steelmaking, water treatment, and the production of cement, paper, and chemicals. It is also used in agriculture to neutralize acidic soils.

Ca(OH)₂ (Calcium Hydroxide):

Properties: It is a white powder with low solubility in water. It forms a strong alkaline solution.
Uses: Calcium hydroxide, commonly known as slaked lime, is used in construction (mortar and plaster), wastewater treatment, and as a pH regulator in agriculture. It is also used in food processing (pickling) and as an ingredient in toothpaste and antacids.

CaSO₄ (Calcium Sulfate):

Uses: Calcium sulfate is commonly found in two forms:
Gypsum (CaSO₄·2H₂O): Used in the construction industry for making plaster of Paris, plasterboard, and cement.
Anhydrous Calcium Sulfate (CaSO₄): Used in agriculture as a soil conditioner and in brewing as a water conditioner.

Plaster of Paris:

Properties: It is a white powder that hardens when mixed with water.
Uses: Plaster of Paris, made by heating gypsum to remove water molecules, is used in construction for making casts, molds, and sculptures. It is also used in medicine for casting broken limbs and in dentistry for making dental impressions. Additionally, it finds applications in art and crafts for creating sculptures and decorative items.

Frequently Asked Questions

The s-block of the periodic table contains a total of 14 elements. These include the alkali metals (Group 1) and the alkaline earth metals (Group 2), which collectively occupy the s orbital in their outermost electron shell.

While both groups are highly reactive, alkali metals are more reactive than alkaline earth metals. Alkali metals have one valence electron to lose in forming an ion, whereas alkaline earth metals have two. The second ionization energy of alkaline earth metals (the energy required to remove a second electron) adds an extra step and more energy compared to alkali metals, making them slightly less reactive.

Alkali Metals (e.g., Sodium and Potassium): Used in various applications such as street lighting (sodium vapor lamps), fertilizers (potassium compounds), and in some types of glass manufacturing. Alkaline Earth Metals (e.g., Magnesium and Calcium): Magnesium is used in lightweight alloys and fireworks, while calcium is crucial in the production of cement and when extracted from limestone, is used in the steelmaking process.

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s-block Elements

1.0What are s-block Elements?

2.0Electronic Configuration of s-block Elements

3.0Properties of s block

Physical Properties of s-block Elements

Chemical Properties of s-block Elements

4.0Important Compounds of s-block Elements

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