Why metal in the middle of metal activity series can't be obtained by heating ors in air​

See Explanation

Explanation:

The way by which a metal is obtained from its ore is determined by the chemical reactivity of the metal.

Metals that are highly reactive are chiefly obtained by electrolysis of the metal salt. These metals are found high up in the metal activity series.

Metals that are at the middle of the series are moderately reactive and are obtained by electrolysis or by reduction since they still form ionic salts.

Metals that are far lower in the series can only be obtained by heating them in air because they are mostly unreactive.

Hence, moderately reactive metals at the middle of the series are not obtained by roasting in air.

it is called acid bonding

the dissolution of polymer can be thermodynamically described in 2 steps.