TOPIC 2 : GROUP 2

PROPERTIES OF GROUP 2

-the elements in group 1 and 2 have larger atomic radii than other elements within the periods
-this is because the outer s electrons are held relatively weakly by the nucleus

1. Going down group 2 , atomic radius increase and effective nuclear charge decrease, the force of attraction between nucleus to the outer electrons decrease. The electrons are removed more easily hence the ionisation energy decrease

2. Melting point decrease when going down group 2 because the metallic bonds get weaker as the atomic size increase

3. Metals have lower electronegativities than non metals, all group 2 elements have low electronegativites. the decrease in electronegativities down group 2 indicates an increase in metallic character

CHEMICAL PROPERTIES OF GROUP 2 ELEMENTS 

-Alkaline earth metals are easily oxidised and are very good reducing agents
-the group 2 elements occurs as 2+
-going down group 2 , the elements become more reactive down the group and more electropositve as it becomes easier to form 2+ ions
-the E values become more negative down the group  which indicates the increase in reducing power

ANOMALOUS BEHAVIOR OF BERYLIUM

-the compound of berylium have significant covalent character while the compounds of other group 2 elements are ionic
-berylium atom has a very high ionisation energy due to the small atomic size and low screening effect
-berylium ion has a very high charge density and high polarising power

1. BERYLIUM CHLORIDE

-is a covalent compound while the other group 2 chlorides are ionic
-berylium chloride is a white solid that sublimes when heated and is soluble in non polar organic solvents
-at room temperature , berylium exist as dimer be2cl4 by forming coordinate bonds between the lone pair electrons
-berylium chloride is hydrolysed exothermically by water liberating acidic , steamy white fumes of hydrogen chloride gas
-beryllium chloride does not conduct electricity in molten state

2. BERYLLIUM OXIDE AND BERYLLIUM HYDROXIDE

-shows amphoteric
-other group 2 elements only react with acids
-beryllium can form complexes , this is due to the charge and small size of be2+ ion. The other group 2 elements rarely form complexes