Question

what is penultimate shell?​

Answer 1

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Answer 2

The electrons are arranged in an atom in the various shells around the nucleus. 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 shell and the one inner to penultimate shell is called theinnermost or anti-penultimate shell.

If ‘n’ is the valence shell then (n-1) is the penultimate shell & (n-2) is the anti-penultimate shell.

Transition elements contain unpaired electrons in penultimate d-subshells.