Question

Why is k is highly reactive metal whereas gold is noble metal?

Answer 1

because potassium being in group 1 has 1 electrons in its valence shell therefore a donates it and is very reactive but in case of gold it has more than 4 electrons in its valence shell so it is a Noble metal and generally it does not easily reacts with other metals are acids

Answer 2

Answer:

 potassium and gold have 1 electron in the outer most shell but nucleus of gold is very large than potassium and can bind all electrons together so it is less reactive unlike potassium which has less nuclear charge and give 1 electron easily from its outer shell and react with other elements.