NEET Study Notes for S-Block elements

NEET Study Notes for S- block elements: S block elements consist of Group 1 and Group 2 elements. These consist of elements with either 1 or electrons in the s-subshell. The elements with 1 electrons are called Group 1 elements or alkali metals while elements with 2 electrons are called Group 2 elements or alkaline earth metals.

• Group 1 elements are Lithium, Sodium, Potassium, Potassium, Rubidium Caesium and Francium. Group 2 elements consist of Beryllium, Magnesium, Calcium, Strontium, Barium and Radium.
• NEET Chemistry Syllabus is divided into - Organic, Inorganic and Physical Chemistry. S blocke elements is a part of Inorganic chemistry which has a weightage of around 34%.
• NEET Study Notes for S-block elements consists of nomenclature, structure, physical and chemical properties of alkali and alkaline earth metals which will help in NEET 2022. Preparation.

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Important Topics in S- block elements

Group 1- Alkali Metals

Due to the looselh held electrons, alkali metals have high electropositivity. This is why they arenot available in free state. The general electronic configuration for Group 1 S block elements are tabulated bellow;

Properties of Alkali Metals

• Atomic Radii- atomic radii of alkali metals is greater in comparison to alkaline earth metals due to the increase in nuclear charge of these elements. The atomic number increases down the group, which results in increase in atomic radii of alkali metals.
• Density- Alkali metals have lower density. Due to increase in atomic size and mass, density increases from li to Cs while density of alkaline earth metals is higher. Due to the difference in crystal structure, density decreases from Be to Ca and then steadily increases from Ca to Ra.
• Melting and Boiling Point- The melting and boiling point of alkaline earth metals is higher than alkali earth metals as the bonding electrons is two,. In alkali metals, boiling and melting point is low and decreases down the group. At room temperature, Fr is liquid.
• Metallic characteristics- Alkaline earth metals are garder due to the metallic bonding in comparison to alkali metals which are malleable and ductile in nature.
• Ionization Enthalpy- Ionization Ionization Enthalpy decreases due to the increase in atomic number. However the I.E of alkaline earth metals is higher than alkali metals I.E of radium is higher than barium.
• Hydration Enthalpy- Hydration Enthapy decreases with an increase in the atomic size. On decrease of the atomic size, large number of water molecules can be accomodated. This results in high enthalpy on increase of the atomic size.

Also Read

• NEET Study Notes on Solid State
• NEET Study Notes for Aldehydes, Ketones and Carboxylic Acid

Diagonal Relationship with S block elements

The relationship between adjacent elements that are present in the second and third periiod is termed as the diagonal relationship between S block elements. Here the properties of elements that are diaogonally located, show similar characteristics.

For example- berrilyium (located in 2nd group and 2nd period ) have similar properties to allumnium ( located in 3rd group and 3rd period). Diagonal relationship between S block elements is witnessed from left to right and down the group.

For Example- Berrylium and and Allumnium

Berrylium and Allumnium Ions are when beryllium hydroxide and allumnium hydroxide reacts with alkali in excess. The presence of oxide, prevents these elements to get affected acid attack. Berrylium and Allumnium tend to form complex compounds. In organic solvents, chlorides of the elements are soluble.

Chemical Properties

Due to the large atomic size and consequent decrease of I.E. alkali metals alkali metals except Lithium form Ionix xompounds. Lithium can form covalent as well as ionic compounds. Alkali metlas are highly reactive.

Reactivity with water

Alkali Metals react with water and forms Hydrogen

Examples of this reaction are 

where M is any alkali metal

Reactivity with water increases down the group from Li to Cs in the following order. This is due to increase in electropositive nature

Li<Na<K<Rb<Cs

Reaction with Hydrogen

Ionic Hydrides are form on reaction of alkali metals with Hydrogen. Down the group, reactivity with hydrogen decreases. This order is

Li>Na>K>Rb>Cs

Stability of these Hydrides in increasing order is LiH>NaH>KH>RbH>CsH

Reaction with Oxygen

On heating alkali metals with Oxygen, oxides like lithium oxide, sodium oxide and sodium peroxide are formed. Lattice energy helps in stabilisation of larger anions through the larger cations. Stability of these oxides and peroxides formed increases from Li to Cs due to this.

Oxides, Peroxides and Superoxides have basic nature. Solubility and increase in oxide strength in increasing order is

Stability of peroxides and superoxided in the increasing order is

Reaction with Halogens

Ionic Halides are formed on reaction of alkali metals with Hydrogen. Reactivity with Halogens in increasing order is

These alkali halides are soluble in water.

Also Read

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Alkaline Metals

These are less reactive in relation to alkali metals as the Ionization enthalpy is low. The reaction increases down the group due to decreasing ionization enthalpy

Reaction with water

Hydrogen gas is formed on reaction of alkaline metals with water. On moving from Mg to Ba reaction of alkaline metals with water inctreases. However Ba reacts vigorously even with cold eater . In the increasing order of reactivity with water is

Mg<Ca<Sr<Ba

Reaction with Hydrogen

Hydides are formed on reaction of alkaline metals with hydrogen through the process of heating. Only Be does not react with Hyrogen These hyides also react with water to form Hydrogen gas. These also behave as strong reducinga agents.

Example- 

Reaction with Halogens

Halides are formed un when these elements react with halogen at high temperature. The hallides have solubility in water. As the atomic size increases, their ionic character also increases.

Reaction with Oxygen

Reactivity with Oxygen increases as we move down the group. Be, Mg and Ca formsmonoxides on heating with oxygen while peroxides from Sr, Ba and Ra.

Example-  

Sodium Carbonate

Sodium Carbonate is a white powder and odourless diaozium salt of carbonic acid. It dissolves in water to form to form carbonic acid and sodium hydroxide. Sodium carbonate is also known as washing soda, soda crystals. Washing soda or soda crystals.

The four main ways of preparation of Sodium Carbonate is Solvay, Labnac, Dual and electrolytic process.

• The chemical formula of sodium carbonate is Na2CO3. The melting and boiling point of sodium carbonate is 1600 C or 810 C.
• The release of OH- aq ions ensure that the aqueous solution of sodium carbonate are mildly alkaline.
• Sodium Hydrogen Carbonate is formed when carbon dioxide present in air is absorbed by sodium carbonate (acqueous solution).

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Sodium Chloride

The ionic compound in which the proportion os sodium and ions is in equal ratio is called Sodim Chloride. Chemical formula of Sodium Chloride is NaCl, Sodium Chloride has wide applications in household as well as industries. The common name of sodium chloride is table salt,common salt and halite.

• Sodium Chloride is water soluble but not soluble or partially soluble in other liquids.
• Ions are freely movable in liquid state of NaCL, which makes a good conductor of electrocity.
• IT is used as a food preservative and also as a raw material in industries.
• The melting point and boiling point of sodium chloride is 801 c amd 1413 C.

Sodium Hydroxide

Sodium oxide is a simple inorganic compound that is in the form of a solid state in white color at room temperature. Ph of a substance can be determined by using sodium hydroxide with neutral water and acid. The chemical formular of Sodium Hydroxide is NaOH. It is also known as caustic soda and manufacturing products like paper, soap, detergents, explosives and cleaners etc.

• Sodium Hydroxide is a white odourless crystalline solid.
• It is water soluble and this is a highly exothermic reaction and also soluble in glycerol and ethanol .
• Sodium Hydroxide also exists in liquid form and is able to carbon dioxide and water.
• Sodium Hydroxide can form Hydrates like Dihydrate, Monohydrate, Pentahydrate, Trihydate etc.
• Sodium Hydroxide can be prepared from- Leblanc, Weldon’s, Deacon and Electrolytic process.

Must Read

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• NEET Study Notes on Structure of Atom

Sodium Bicarbonate

Sodium Bicarbonate, also known as Sodium hydrogen carbonate is a white powder like substance. It is formed from sodium and bicarbonate ions. This is also known as baking soda. The chemical formula of Sodium bicarbonate is NaHCO3.

• The melting and boiling point of sodium bicarbonate is 851 and 50 C respectively.
• It is soluble in methanol and acetone but insoluble in ethanol.
• Sodium bicarbonate can be used as disinfectant, pest control, baking, clean kitchen products, medicinal purposes.

NEET Sample MCQs on S-block elements

Question: Element of atomic number 56 belongs to which of the following group

1. f-block
2. d-block
3. s-block
4. P-block

Answer: s- block

Question: Why are the properties of Lithium and Magnesium similar?

1. Due to diagonal relationship
2. As they belong to the same group
3. Ionization Energy is same
4. Electron affinity is same

Answer: Due to diagonal relationship

Question: Potassium is an element from which of the following groups?

1. Halogens
2. Alkali metals
3. Alkaline earth metals
4. Noble gases

Answer: Alkali Metals

Question: In comparison to K, Na has a

1. Large atomic radius
2. Lower melting point
3. Lower electronegativity
4. Higher Ionization enthalpy

Answer: higher ionization energy

Question: With which element is the diagonal relationship of Be seen?

1. B
2. Mg
3. Al
4. Na

Answer: Al

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