Explain the physical properties of alkaline earth metals (Group $2$).

(N/A) The alkaline earth metals are generally silvery white,lustrous,and relatively soft,though they are harder than the alkali metals.
$Be$ and $Mg$ appear somewhat greyish. The melting and boiling points of these metals are higher than the corresponding alkali metals due to their smaller atomic sizes.
However,the trend in melting and boiling points is not entirely systematic. Due to their low ionisation enthalpies,they are strongly electropositive in nature.
The electropositive character increases down the group from $Be$ to $Ba$. $Ca$,$Sr$,and $Ba$ impart characteristic brick red,crimson,and apple green colours to the flame,respectively.
In the flame,electrons are excited to higher energy levels,and when they return to the ground state,energy is emitted as visible light.
The electrons in $Be$ and $Mg$ are too strongly bound to be excited by the flame,so they do not impart any colour.
The flame test for $Ca$,$Sr$,and $Ba$ is useful for their detection in qualitative analysis and estimation via flame photometry.
Like alkali metals,alkaline earth metals exhibit high electrical and thermal conductivities,which are typical metallic characteristics.