11.1    Physical Properties of  Group II Elements

Introduction to Group II  elements

• Group II elements(also called the ‘alkaline earth metals’) are s-block elements with a characteristic outer shell configuration ns².

• Group II elements are very reactive metals. They have low electronegativity and are readily oxidised, they always exhibit an oxidation state of +2 in their compounds. This is because the two outer s electrons are readily lost during a reaction to achieve a noble gas configuration

M → M²⁺ + 2e⁻     ; where M = A Group II element

Variation in atomic radius

1) The atomic radius increases going down the Group. This is because going down the Group, each succeeding element has one more shell of electrons. The distance between nucleus and outer electrons are progressively further.

Variation in first ionisation energy

• The first ionisation energy decreases down the This is because the distance between nucleus and outer electrons increases, and the outer electrons are more shielded.

• These two factors outweigh the increasing nuclear So, the attractive force between nucleus and outer electrons decreases and less energy is required to remove the electron.

Variation in electronegativity

• Electronegativity decreases down the This is because the distance between the nucleus and the bonded pair of electrons increases down the Group. Therefore the electrons are held less strongly by the nucleus.

• In other words, the reducing power(and reactivity) increases down the Group