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Group-1 Elements: The Alkali Metals
Chapter Name : The S- Block Elements
Sub Topic Code : 102_11_10_02_04
Topic Name : Group-1 Elements: The Alkali Metals
Sub Topic Name : Hydration Enthalpy
Introduction

• Group 1 of the Periodic Table consists of the elements: lithium, sodium, potassium, rubidium, cesium and francium. • They are collectively known as the alkali metals. • These are so called because they form hydroxides on reaction with water which are strongly alkaline in nature. • Hydration Enthalpy, defined as the enthalpy change observed when one mole of gaseous ions is completely dissolved in water forming one mole of aqueous ions. • The hydration enthalpies of alkali metal ions decrease with increase in ionic sizes. Li+> Na+ > K+ > Rb+ > Cs+ • Li+ has maximum degree of hydration and for this reason lithium salts are mostly hydrated, e.g., LiCl• 2H2O.

Pre-Requisites:

Alkali metals, periodic table, s-block

Activity:

Nerve impulse conduction, Sodium is a primary ingredient of common salt.

Real Life Question:

How do nerve impulses work?

Key Words / FlashCards
Key Words Definitions (pref. in our own words)
Alkali metals • Group 1 elements.
Learning aids / Gadgets
Gadgets How it can be used
needle Prick your finger with a needle lightly. See how the nerve impulse travels through and reaches the brain detecting pain. Sodium calcium and Potassium ions play a major role in nerve impulse conduction.
Real life uses :

Nerve impulse conduction.

Places to visit :

Kitchen.

Practical examples around us
Examples Explainations
salt Salt contains sodium.
What you learn in Theory:

• Hydration Enthalpy, defined as the enthalpy change observed when one mole of gaseous ions is completely dissolved in water forming one mole of aqueous ions. • The hydration enthalpies of alkali metal ions decrease with increase in ionic sizes. Li+> Na+ > K+ > Rb+ > Cs+ • Li+ has maximum degree of hydration and for this reason lithium salts are mostly hydrated, e.g., LiCl• 2H2O.

What you learn in Practice:

• Hydration Enthalpy, defined as the enthalpy change observed when one mole of gaseous ions is completely dissolved in water forming one mole of aqueous ions. • The hydration enthalpies of alkali metal ions decrease with increase in ionic sizes. Li+> Na+ > K+ > Rb+ > Cs+ • Li+ has maximum degree of hydration and for this reason lithium salts are mostly hydrated, e.g., LiCl• 2H2O.

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