Introduction

• The alkaline earth metals, in general, are silvery white, lustrous and relatively soft but harder than the alkali metals. • Beryllium and magnesium appear to be somewhat greyish. • The melting and boiling points of these metals are higher than the corresponding alkali metals due to smaller sizes. • Because of the low ionisation enthalpies, they are strongly electropositive in nature. The electropositive character increases down the group from Be to Ba. • In flame the electrons are excited to higher energy levels and when they drop back to the ground state, energy is emitted in the form of visible light. • The electrons in beryllium and magnesium are too strongly bound to get excited by flame. Hence, these elements do not impart any colour to the flame. • The alkaline earth metals like those of alkali metals have high electrical and thermal conductivities which are typical characteristics of metals.

Pre-Requisites:

Alkali earth metals, elements, periodic table, physical properties

Activity:

Bones and teeth have calcium in them.

Real Life Question:

Where do you find calcium in the body?

Key Words / FlashCards

Learning aids / Gadgets

Real life uses :

Calcium is important for the bone and teeth development.

Places to visit :

Kitchen.

Practical examples around us

What you learn in Theory:

• Like alkali metal ions, the hydration enthalpies of alkaline earth metal ions decrease with increase in ionic size down the group. • The hydration enthalpies of alkaline earth metal ions are larger than those of alkali metal ions. • Thus, compounds of alkaline earth metals are more hydrated than those of alkali metals. • E.g., MgCl2 and CaCl2 exist as MgCl2.6H2O and CaCl2• 6H2O while NaCl and KCl do not form such hydrates.

What you learn in Practice:

• Important ions for the body like calcium and magnesium belong to group 2 in the periodic table.