Question

What is the difference between penultimate shell and valence shell?

Answer 1

The last shell or the outer most shell from the nucleus is called the valence shell. The shell inner to this is called the inner shell or penultimate

The valence shell is the outer shell of the atom. Some materials have a free electron in their valence shell and this electron can easily move from atom to atom. The free electrons are responsible for electrical current.

Answer 2

valence shell is the last shell of the atom containing valence electrons. this shell is also known as Ultimate shell. Penultimate shell is the shell just before the valence or the ultimate shell . i.e.,the second last shell of the atom.