General Characteristics Of The Compounds Of Alkaline Earth Metals
Chapter Name : The S- Block Elements |
Sub Topic Code : 102_11_10_08_01 |
Topic Name : General Characteristics Of The Compounds Of Alkaline Earth Metals |
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Sub Topic Name : General Characteristics Of The Compounds Of Alkaline Earth Metals |
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Introduction
• The oxidation state of +2 is the main valence of Group 2 elements. • The alkaline earth metals form compounds which are mainly ionic but less ionic than the corresponding compounds of alkali metals. This is due to increased nuclear charge and smaller size. • The oxides and other compounds of beryllium and magnesium are more covalent than those formed by the Ca, Sr and Ba. • BeO is covalent in nature, while oxides of other elements are ionic in nature • BeO is amphoteric (reacts with acid and alkali both) • All these oxides except BeO are basic in nature and react with water to form sparingly soluble hydroxides. • The tendency to form halide hydrates gradually decreases (for example, MgCl2•8H2O, CaCl2•6H2O, SrCl2•6H2O and BaCl2•2H2O) down the group. • The dehydration of hydrated chlorides, bromides and iodides of Ca, Sr and Ba can be achieved on heating; however, the corresponding hydrated halides of Be and Mg on heating suffer hydrolysis. • The fluorides are relatively less soluble than the chlorides owing to their high lattice energies. • Carbonates of alkaline earth metals are insoluble in water and can be precipitated by addition of a sodium or ammonium carbonate solution. • The sulphates of the alkaline earth metals are all white solids and stable to heat.
Pre-Requisites:
Alkali earth metals, elements, periodic table
Activity:
Busts and statues are sometimes made of Calcium carbonate (an Oxoacid salt of calcium).
Real Life Question:
What is the Taj mahal made of?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Alkaline earth metals | • Group 2 elements. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Periodic table | Look at the elements present in the group 2 of the periodic table. |
Real life uses :
Calcium is important for the bone and teeth development.
Places to visit :
Kitchen, parks, museum.
Practical examples around us
| Examples | Explainations |
|---|---|
| Milk, yogurt | These are rich sources of calcium. |
What you learn in Theory:
• The oxidation state of +2 is the main valence of Group 2 elements. • The alkaline earth metals form compounds which are mainly ionic but less ionic than the corresponding compounds of alkali metals. This is due to increased nuclear charge and smaller size. • The oxides and other compounds of beryllium and magnesium are more covalent than those formed by the Ca, Sr and Ba. • BeO is covalent in nature, while oxides of other elements are ionic in nature • BeO is amphoteric (reacts with acid and alkali both) • All these oxides except BeO are basic in nature and react with water to form sparingly soluble hydroxides. • The tendency to form halide hydrates gradually decreases (for example, MgCl2•8H2O, CaCl2•6H2O, SrCl2•6H2O and BaCl2•2H2O) down the group. • The dehydration of hydrated chlorides, bromides and iodides of Ca, Sr and Ba can be achieved on heating; however, the corresponding hydrated halides of Be and Mg on heating suffer hydrolysis. • The fluorides are relatively less soluble than the chlorides owing to their high lattice energies. • Carbonates of alkaline earth metals are insoluble in water and can be precipitated by addition of a sodium or ammonium carbonate solution. • The sulphates of the alkaline earth metals are all white solids and stable to heat.
What you learn in Practice:
• Important ions for the body like calcium and magnesium belong to group 2 in the periodic table.