NEET Notes: s and p-Block Elements

Introduction

The periodic table is divided into different blocks based on the electronic configuration of elements. The s-block and p-block elements play a crucial role in chemistry, as they include essential metals and non-metals with significant applications in biological, industrial, and environmental processes. Understanding their properties, reactivity, and uses is fundamental for NEET aspirants.

s-Block Elements (Group 1 and Group 2)

1. General Characteristics of s-Block Elements

• These elements have their outermost electron(s) in the s-orbital.

• Group 1 elements (alkali metals) and Group 2 elements (alkaline earth metals) belong to this block.

• They are highly reactive and occur naturally in combined forms.

• Show metallic character and low electronegativity.

• Form strong bases (alkalis) when reacted with water.

2. Alkali Metals (Group 1: Li, Na, K, Rb, Cs, Fr)

(a) Physical Properties

• Soft metals with low density.

• Low melting and boiling points.

• Excellent conductors of heat and electricity.

• Highly reactive, especially with water and oxygen.

(b) Chemical Properties

• React with water to form hydroxides and hydrogen gas.

• React with halogens to form ionic salts (e.g., NaCl, KBr).

• Show strong reducing properties due to low ionization energy.

(c) Important Compounds of Alkali Metals

• Sodium Hydroxide (NaOH): Used in soap-making and paper industries.

• Sodium Carbonate (Na₂CO₃): Used in glass manufacturing.

• Potassium Nitrate (KNO₃): Used in fertilizers and explosives.

3. Alkaline Earth Metals (Group 2: Be, Mg, Ca, Sr, Ba, Ra)

(a) Physical Properties

• Harder and denser than alkali metals.

• Higher melting and boiling points.

• Good conductors of electricity.

(b) Chemical Properties

• Less reactive than alkali metals but still form oxides and hydroxides.

• React with water to form weak bases (e.g., Ca(OH)₂ - slaked lime).

• Form ionic compounds, except for beryllium which forms covalent compounds.

(c) Important Compounds of Alkaline Earth Metals

• Calcium Carbonate (CaCO₃): Found in limestone and marble, used in cement.

• Magnesium Sulfate (MgSO₄): Used as Epsom salt in medicine.

• Barium Sulfate (BaSO₄): Used in medical X-rays for imaging.

p-Block Elements (Groups 13 to 18)

1. General Characteristics of p-Block Elements

• The outermost electron(s) are in the p-orbital.

• Groups 13 to 18 belong to this block, consisting of metals, metalloids, and non-metals.

• Reactivity varies widely across the groups.

• Exhibit multiple oxidation states and form covalent as well as ionic compounds.

2. Group 13: Boron Family (B, Al, Ga, In, Tl)

(a) Physical Properties

• Boron is a metalloid; others are metals.

• Good electrical and thermal conductors.

• Low melting and boiling points (except boron).

(b) Chemical Properties

• Show oxidation states of +3 (common) and +1 (in heavier elements).

• Form oxides and hydroxides (e.g., B₂O₃, Al₂O₃).

(c) Important Compounds

• Boric Acid (H₃BO₃): Used in antiseptics.

• Aluminum Oxide (Al₂O₃): Used in ceramics and abrasives.

3. Group 14: Carbon Family (C, Si, Ge, Sn, Pb)

(a) Physical Properties

• Carbon is a non-metal, silicon and germanium are metalloids, tin and lead are metals.

• Exhibit allotropic forms (e.g., graphite and diamond for carbon).

(b) Chemical Properties

• Show oxidation states of +4 and +2 (lead prefers +2 due to inert pair effect).

• React with oxygen to form oxides (CO₂, SiO₂).

(c) Important Compounds

• Silicon Dioxide (SiO₂): Used in glass and electronics.

• Lead Acetate (Pb(C₂H₃O₂)₂): Used in hair dyes.

4. Group 15: Nitrogen Family (N, P, As, Sb, Bi)

(a) Physical Properties

• Nitrogen and phosphorus are non-metals, arsenic and antimony are metalloids, bismuth is a metal.

(b) Chemical Properties

• Show oxidation states of -3, +3, and +5.

• Form oxides and acidic or basic compounds.

(c) Important Compounds

• Ammonia (NH₃): Used in fertilizers.

• Phosphoric Acid (H₃PO₄): Used in soft drinks and detergents.

5. Group 16: Oxygen Family (O, S, Se, Te, Po)

(a) Physical Properties

• Oxygen and sulfur are non-metals, selenium and tellurium are metalloids, polonium is a metal.

(b) Chemical Properties

• Show oxidation states of -2, +2, +4, and +6.

• Form acidic oxides and sulfides.

(c) Important Compounds

• Sulfuric Acid (H₂SO₄): Used in batteries and fertilizers.

• Selenium Dioxide (SeO₂): Used in xerography.

6. Group 17: Halogens (F, Cl, Br, I, At)

(a) Physical Properties

• Exist as diatomic molecules (F₂, Cl₂, Br₂, I₂).

• Have strong oxidizing properties.

(b) Chemical Properties

• Show oxidation states of -1, +1, +3, +5, and +7.

• React with metals to form halide salts.

(c) Important Compounds

• Hydrochloric Acid (HCl): Used in food processing and cleaning.

• Sodium Hypochlorite (NaOCl): Used as bleach.

7. Group 18: Noble Gases (He, Ne, Ar, Kr, Xe, Rn)

(a) Physical Properties

• Colorless, odorless, and inert gases.

• Low boiling and melting points.

(b) Chemical Properties

• Least reactive due to fully filled valence shells.

• Xenon forms compounds with fluorine and oxygen (XeF₂, XeO₄).

(c) Uses of Noble Gases

• Helium: Used in balloons and cryogenics.

• Neon: Used in neon sign lighting.

• Argon: Used in welding and light bulbs.

Conclusion

The s-block and p-block elements play a crucial role in chemistry and industry. Alkali and alkaline earth metals are highly reactive and essential for biological and industrial applications. The p-block elements exhibit diverse properties, forming a variety of compounds essential for environmental, technological, and medical applications. Understanding their behavior and reactions is key for mastering inorganic chemistry in NEET preparation.