Explain the following:
a. Alkali metals are paramagnetic, but their salts are diamagnetic.
b. The inside surface of a glass bottle containing caustic sada becomes dull.

Explanation

a. The general electronic congiguration of alkali metals is `ns^(1)`, i.e. alkali metals have one unpaired etectron in their valence shells and hence they are paramagnetic. Alkali metal salts are ionic in nature, i.e. alkali metals lose the valence shell electron to form unpiositive cation and non-metal acceprt this electrons to form uninegative ion and thus all the electrons are paired up and hence alkali metal salts are diamagnetic.
b. Glass contains silica. It slowly dissolves in NaOH and forms soluble sodium silicate and thus the inside surface becomes dull.
`2Naoh+2sIo_(2)rarr 2NaSiO_(3)+H_(2)`