Answer:
The electronic configuration uses the principle of the K,L,M,N shells to arrange electrons in the shells of elements. The K shell which is the first shell can only accommodate two electrons while the rest shells can accommodate a maximum of 8 electrons. Metals and nonmetals have atomic numbers which tells us the amount of electrons they contain in their neutral state.
For example the metal Sodium (Na) has an atomic number of 11.The electronic configuration will be; 2,8,1 .
The non metal Chlorine has an atomic number of 17. The electron configuration will be 2,8,7
The valence shell refers to the last shell of an atom.
We can see from the electronic configurations that sodium has 1 electron in its valence shell, while chlorine has 7 electrons in its valence shell. Generally non-metals gain electrons because of the large number of electrons in their valence shell and metals lose electrons due to the fewer number of electrons in their valence shell
