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 |
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Sub Topic Name : Hydration Enthalpy |
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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.